[v4,02/21] nptl: Fix Race conditions in pthread cancellation [BZ#12683]

Message ID 20200403203201.7494-3-adhemerval.zanella@linaro.org
State New
Headers show
Series
  • nptl: Fix Race conditions in pthread cancellation [BZ#12683]
Related show

Commit Message

Sergei Trofimovich via Libc-alpha April 3, 2020, 8:31 p.m.
This patch is the initial fix for race conditions in NPTL cancellation
code by redefining how cancellable syscalls are defined and handled.
The current buggy approach is to enable asynchronous cancellation
before making the syscall and restore the previous cancellation
type once the syscall returns.

As described in BZ#12683, this approach shows 2 important problems:

  1. Cancellation can act after the syscall has returned from the
     kernel, but before userspace saves the return value.  It might
     result in a resource leak if the syscall allocated a resource or a
     side effect (partial read/write), and there is no way to program
     handle it with cancellation handlers.

  2. If a signal is handled while the thread is blocked at a cancellable
     syscall, the entire signal handler runs with asynchronous
     cancellation enabled.  This can lead to issues if the signal
     handler call functions which are async-signal-safe but not
     async-cancel-safe.

For the cancellation to work correctly, there are 5 points at which the
cancellation signal could arrive:

  1. Before the final "testcancel" and before the syscall is made.
  2. Between the "testcancel" and the syscall.
  3. While the syscall is blocked and no side effects have yet taken
     place.
  4. While the syscall is blocked but with some side effects already
     having taken place (e.g. a partial read or write).
  5. After the syscall has returned.

And GLIBC wants to act on cancellation in cases 1, 2, and 3 but not
in cases 4 or 5.  For the 4 and 5 cases, the cancellation will eventually
happen in the next cancellable entry point without any further external
event.

The proposed solution follows for each case:

  1. Do a conditional branch based on whether the thread has received
     a cancellation request;

  2. It can be caught by the signal handler determining that the saved
     program counter (from the ucontext_t) is in some address range
     beginning just before the "testcancel" and ending with the
     syscall instruction.

  3. In this case, except for certain syscalls that ALWAYS fail with
     EINTR even for non-interrupting signals, the kernel will reset
     the program counter to point at the syscall instruction during
     signal handling, so that the syscall is restarted when the signal
     handler returns.  So, from the signal handler's standpoint, this
     looks the same as case 2, and thus it's taken care of.

  4. For syscalls with side-effects, the kernel cannot restart the
     syscall; when it's interrupted by a signal, the kernel must cause
     the syscall to return with whatever partial result is obtained
     (e.g. partial read or write).

  5. In this case, the saved program counter points just after the
     syscall instruction, so the signal handler won't act on
     cancellation.  This is similar to 4. since the program counter
     is past the syscall instruction.

Another case that needs handling is syscalls that fail with EINTR even
when the signal handler is non-interrupting. In this case, the syscall
wrapper code can just check the cancellation flag when the errno result
is EINTR, and act on cancellation if it's set.

The proposed GLIBC adjustments are:

  1. Remove the enable_asynccancel/disable_asynccancel function usage in
     syscall definition and instead make them call a common symbol that
     will check if cancellation is enabled (__syscall_cancel at
     nptl/libc-cancellation.c), call the arch-specific cancellable
     entry-point (__syscall_cancel_arch) and cancel the thread when
     required.

  2. Provide an arch-specific generic system call wrapper function
     that contains global markers.  These markers will be used in
     SIGCANCEL handler to check if the interruption has been called in a
     valid syscall and if the syscalls have been completed or not.

     A reference implementation sysdeps/unix/sysv/linux/syscall_cancel.c
     is provided.  However, the markers may not be set on correct
     expected places depending on how INTERNAL_SYSCALL_NCS is
     implemented by the architecture and it uses compiler-specific
     construct (asm volatile) to place the required markers.
     It is expected that all architectures add an arch-specific
     implementation.

  3. Rewrite SIGCANCEL asynchronous handler to check for both canceling
     type and if current IP from signal handler falls between the global
     markers and act accordingly (sigcancel_handler at nptl/nptl-init.c).

  4. Adjust nptl/pthread_cancel.c to send a signal instead of acting
     directly. This avoids synchronization issues when updating the
     cancellation status and also focuses the logic on the signal
     handler and cancellation syscall code.

  5. Adjust pthread code to replace CANCEL_ASYNC/CANCEL_RESET calls to
     appropriated cancelable futex syscalls.

  6. Adjust libc code to replace LIBC_CANCEL_ASYNC/LIBC_CANCEL_RESET to
     appropriated cancelable syscalls.

  7. Adjust 'lowlevellock-futex.h' arch-specific implementations to
     provide cancelable futex calls (used in libpthread code).

This patch adds the proposed changes to NPTL common code and the
following patches add the requires arch-specific bits.  The build for
ia64-linux-gnu, mips-*, and x86_64-* are broken without the
arch-specific patches.

As a side note regarding SIGCANCEL and SIGTIMER being the the same,
it should not impact timer_create functionality.  It arranges for
SIGCANCEL/SIGTIMER to be sent to the internal helper thread, which
in turn check if the si.si_code is SI_TIMER and call pthread_exit
otherwise (sysdeps/unix/sysv/linux/timer_routines.c:129).

This suggests that the helper thread does NOT depend on EINTR
being generated for SIGCANCEL/SIGTIMER, and it should be fine to use
SA_RESTART for that signal as far as timer_create is concerned.
---
 manual/llio.texi                              |   4 +-
 nptl/Makefile                                 |  10 +-
 nptl/Versions                                 |   4 +
 nptl/cancellation.c                           |  78 ------------
 nptl/descr.h                                  |   3 -
 nptl/libc-cancellation.c                      |  43 ++++++-
 nptl/nptl-init.c                              |  92 +++++++-------
 nptl/pthreadP.h                               |  57 ++++++---
 nptl/pthread_cancel.c                         |  66 +++-------
 nptl/pthread_create.c                         |   7 +-
 nptl/pthread_exit.c                           |   9 +-
 nptl/pthread_join_common.c                    |   7 +-
 nptl/pthread_kill.c                           |   7 +-
 .../pthread_kill_internal.c                   |  21 +---
 nptl/pthread_setcanceltype.c                  |   2 +-
 nptl/pthread_testcancel.c                     |  12 +-
 nptl/sem_wait.c                               |   2 +-
 nptl/tst-cancel29.c                           | 100 +++++++++++++++
 rt/Makefile                                   |   2 +-
 .../syscall_types.h}                          |  13 +-
 sysdeps/generic/sysdep-cancel.h               |   2 -
 sysdeps/nptl/Makefile                         |   3 +-
 sysdeps/nptl/cancellation-pc-check.h          |  53 ++++++++
 sysdeps/nptl/cancellation-sigmask.h           |  30 +++++
 sysdeps/nptl/futex-internal.h                 |  19 +--
 sysdeps/nptl/lowlevellock-futex.h             |  41 ++++--
 sysdeps/unix/sysdep.h                         | 118 ++++++++++++++----
 sysdeps/unix/sysv/linux/socketcall.h          |  40 ++++--
 sysdeps/unix/sysv/linux/syscall_cancel.c      |  62 +++++++++
 sysdeps/unix/sysv/linux/sysdep-cancel.h       |  42 -------
 sysdeps/unix/sysv/linux/sysdep.h              |   9 ++
 31 files changed, 591 insertions(+), 367 deletions(-)
 delete mode 100644 nptl/cancellation.c
 rename sysdeps/unix/sysv/linux/pthread_kill.c => nptl/pthread_kill_internal.c (75%)
 create mode 100644 nptl/tst-cancel29.c
 rename sysdeps/{nptl/librt-cancellation.c => generic/syscall_types.h} (70%)
 create mode 100644 sysdeps/nptl/cancellation-pc-check.h
 create mode 100644 sysdeps/nptl/cancellation-sigmask.h
 create mode 100644 sysdeps/unix/sysv/linux/syscall_cancel.c

-- 
2.17.1

Comments

Zack Weinberg April 7, 2020, 6:24 p.m. | #1
On Fri, Apr 3, 2020 at 4:32 PM Adhemerval Zanella via Libc-alpha
<libc-alpha@sourceware.org> wrote:
>

> This patch is the initial fix for race conditions in NPTL cancellation

> code by redefining how cancellable syscalls are defined and handled.

> The current buggy approach is to enable asynchronous cancellation

> before making the syscall and restore the previous cancellation

> type once the syscall returns.


I want to see this bug fixed.  Unfortunately I don't know the guts of
NPTL well enough to review your patches completely, but here are a few
things I noticed:

> As a side note regarding SIGCANCEL and SIGTIMER being the the same,

> it should not impact timer_create functionality.  It arranges for

> SIGCANCEL/SIGTIMER to be sent to the internal helper thread, which

> in turn check if the si.si_code is SI_TIMER and call pthread_exit

> otherwise (sysdeps/unix/sysv/linux/timer_routines.c:129).


Can we be absolutely certain that SIGCANCEL/SIGTIMER will always be
sent to a specific thread and not to a process?

> +  /* Add SIGCANCEL on ignored sigmask to avoid the handler to be called

> +     again.  */

> +  ucontext_block_sigcancel (ctx);

> +

> +  /* Check if asynchronous cancellation mode is set or if interrupted

> +     instruction pointer falls within the cancellable syscall bridge.  For

> +     interruptable syscalls that might generate external side-effects (partial

> +     reads or writes, for instance), the kernel will set the IP to after

> +     '__syscall_cancel_arch_end', thus disabling the cancellation and allowing

> +     the process to handle such conditions.  */

> +  if (self->canceltype == PTHREAD_CANCEL_ASYNCHRONOUS

> +      || cancellation_pc_check (ctx))

> +    __do_cancel (PTHREAD_CANCELED);


Shouldn't this check happen _before_ we block further SIGCANCELs?
If cancellation_pc_check fails, because the signal was delivered on
exit from a system call that has had side effects, don't we need to
be able to receive future SIGCANCELs in order for the next cancellation
point to trigger?

>    /* Install the cancellation signal handler.  If for some reason we

>       cannot install the handler we do not abort.  Maybe we should, but

>       it is only asynchronous cancellation which is affected.  */


1) I think the third sentence of this comment has always been wrong.
2) Perhaps, if we cannot install a handler for SIGCANCEL, we should set
   a global flag which causes all calls to pthread_cancel to fail?

> +    /* Install the handle to change the threads' uid/gid.  */


Typo: handle -> handler (it was wrong before, but you may as well fix it)

> +    struct sigaction sa;

> +    __sigemptyset (&sa.sa_mask);

> +    sa.sa_sigaction = sighandler_setxid;

> +    sa.sa_flags = SA_SIGINFO | SA_RESTART;

> +    __libc_sigaction (SIGSETXID, &sa, NULL);


Unrelated preexisting bug, but I think we probably _should_ crash the
whole process if the SIGSETXID handler cannot be installed,
particularly when __libc_enable_secure is true.

> +  /* Avoid signaling when thread attempts cancel itself (pthread_kill

> +     is expensive).  */

> +  if (pd == THREAD_SELF)

> +    {

> +      if (pd->cancelstate == PTHREAD_CANCEL_ENABLE

> +         && pd->canceltype == PTHREAD_CANCEL_ASYNCHRONOUS)

> +       __pthread_exit (PTHREAD_CANCELED);

> +      return 0;


This works because __pthread_exit is actually a tiny wrapper around
__do_cancel, but I think the logic would be easier to understand,
here, if it called __do_cancel.

zw
Sergei Trofimovich via Libc-alpha April 8, 2020, 2:13 p.m. | #2
On 07/04/2020 15:24, Zack Weinberg wrote:
> On Fri, Apr 3, 2020 at 4:32 PM Adhemerval Zanella via Libc-alpha

> <libc-alpha@sourceware.org> wrote:

>>

>> This patch is the initial fix for race conditions in NPTL cancellation

>> code by redefining how cancellable syscalls are defined and handled.

>> The current buggy approach is to enable asynchronous cancellation

>> before making the syscall and restore the previous cancellation

>> type once the syscall returns.

> 

> I want to see this bug fixed.  Unfortunately I don't know the guts of

> NPTL well enough to review your patches completely, but here are a few

> things I noticed:


Thanks.

> 

>> As a side note regarding SIGCANCEL and SIGTIMER being the the same,

>> it should not impact timer_create functionality.  It arranges for

>> SIGCANCEL/SIGTIMER to be sent to the internal helper thread, which

>> in turn check if the si.si_code is SI_TIMER and call pthread_exit

>> otherwise (sysdeps/unix/sysv/linux/timer_routines.c:129).

> 

> Can we be absolutely certain that SIGCANCEL/SIGTIMER will always be

> sent to a specific thread and not to a process?


With this patch pthread_cancel calls __pthread_kill_internal and
in turn it will use tgkill with process's pid and struct pthread tid.

And Linux timer_create does use the helper thread tid as the target one
(line 148).

> 

>> +  /* Add SIGCANCEL on ignored sigmask to avoid the handler to be called

>> +     again.  */

>> +  ucontext_block_sigcancel (ctx);

>> +

>> +  /* Check if asynchronous cancellation mode is set or if interrupted

>> +     instruction pointer falls within the cancellable syscall bridge.  For

>> +     interruptable syscalls that might generate external side-effects (partial

>> +     reads or writes, for instance), the kernel will set the IP to after

>> +     '__syscall_cancel_arch_end', thus disabling the cancellation and allowing

>> +     the process to handle such conditions.  */

>> +  if (self->canceltype == PTHREAD_CANCEL_ASYNCHRONOUS

>> +      || cancellation_pc_check (ctx))

>> +    __do_cancel (PTHREAD_CANCELED);

> 

> Shouldn't this check happen _before_ we block further SIGCANCELs?

> If cancellation_pc_check fails, because the signal was delivered on

> exit from a system call that has had side effects, don't we need to

> be able to receive future SIGCANCELs in order for the next cancellation

> point to trigger?


For this case the cancellation will happen on next cancellation entrypoint
since pthread_cancel has already set the CANCELED_BIT on the target 
struct pthread cancelhandling member and it will be checked on every 
cancellation entrypoint prior issuing the syscall.

> 

>>    /* Install the cancellation signal handler.  If for some reason we

>>       cannot install the handler we do not abort.  Maybe we should, but

>>       it is only asynchronous cancellation which is affected.  */

> 

> 1) I think the third sentence of this comment has always been wrong.

> 2) Perhaps, if we cannot install a handler for SIGCANCEL, we should set

>    a global flag which causes all calls to pthread_cancel to fail?

> 


The cases I see it might fail are if kernel or some filter (seccomp, bpf,
etc.) explicit disables it. And I am not sure if is up to glibc to actually
handle it, since it would require to:

  1. Set a global flag stating that *asynchronous* thread cancellation is
     not supported at runtime, as you noted.

  2. The pthread_setcanceltype should the check this flag and fail for 
     PTHREAD_CANCEL_ASYNCHRONOUS.

  3. We will need to adjust the code on thread start (START_THREAD_DEFN)
     which set PTHREAD_CANCEL_ASYNCHRONOUS (and as Florian noted, this
     code might be unnecessary).

  4. We will also need to adjust on how to handle
     pthread_cleanup_push_defer_np since __pthread_register_cancel_defer
     also set and reset cancellation type to PTHREAD_CANCEL_ASYNCHRONOUS.

So I am not sure which would be better: 

  1. Do nothing (currently).

  2. Abort in case of an handler installation error.

  3. Disable asynchronous cancellation at runtime.

In any case I think we should discuss in in another thread.

>> +    /* Install the handle to change the threads' uid/gid.  */

> 

> Typo: handle -> handler (it was wrong before, but you may as well fix it)


Ack.

> 

>> +    struct sigaction sa;

>> +    __sigemptyset (&sa.sa_mask);

>> +    sa.sa_sigaction = sighandler_setxid;

>> +    sa.sa_flags = SA_SIGINFO | SA_RESTART;

>> +    __libc_sigaction (SIGSETXID, &sa, NULL);

> 

> Unrelated preexisting bug, but I think we probably _should_ crash the

> whole process if the SIGSETXID handler cannot be installed,

> particularly when __libc_enable_secure is true.


I tend to agree, but is there a real scenario where sigaction syscall
might fail here?

> 

>> +  /* Avoid signaling when thread attempts cancel itself (pthread_kill

>> +     is expensive).  */

>> +  if (pd == THREAD_SELF)

>> +    {

>> +      if (pd->cancelstate == PTHREAD_CANCEL_ENABLE

>> +         && pd->canceltype == PTHREAD_CANCEL_ASYNCHRONOUS)

>> +       __pthread_exit (PTHREAD_CANCELED);

>> +      return 0;

> 

> This works because __pthread_exit is actually a tiny wrapper around

> __do_cancel, but I think the logic would be easier to understand,

> here, if it called __do_cancel.


The idea is eventually just remove __do_cancel and use __pthread_exit
instead internally.  I didn't do it on this patch because it would 
require first to move __pthread_exit to libc.so.

Patch

diff --git a/manual/llio.texi b/manual/llio.texi
index fe59002915..c02ee83428 100644
--- a/manual/llio.texi
+++ b/manual/llio.texi
@@ -2534,13 +2534,13 @@  aiocb64}, since the LFS transparently replaces the old interface.
 @c     sigemptyset ok
 @c     sigaddset ok
 @c     setjmp ok
-@c     CANCEL_ASYNC -> pthread_enable_asynccancel ok
+@c     __pthread_setcanceltype ok
 @c      do_cancel ok
 @c       pthread_unwind ok
 @c        Unwind_ForcedUnwind or longjmp ok [@ascuheap @acsmem?]
 @c     lll_lock @asulock @aculock
 @c     lll_unlock @asulock @aculock
-@c     CANCEL_RESET -> pthread_disable_asynccancel ok
+@c     __pthread_setcanceltype ok
 @c      lll_futex_wait ok
 @c     ->start_routine ok -----
 @c     call_tls_dtors @asulock @ascuheap @aculock @acsmem
diff --git a/nptl/Makefile b/nptl/Makefile
index e554a3898d..0cb724eb76 100644
--- a/nptl/Makefile
+++ b/nptl/Makefile
@@ -60,6 +60,7 @@  routines = \
   pthread_self \
   pthread_setschedparam \
   register-atfork \
+  syscall_cancel
 
 shared-only-routines = forward
 static-only-routines = pthread_atfork
@@ -123,7 +124,8 @@  libpthread-routines = nptl-init nptlfreeres vars events version pt-interp \
 		      pthread_barrierattr_setpshared \
 		      pthread_key_create pthread_key_delete \
 		      pthread_getspecific pthread_setspecific \
-		      pthread_sigmask pthread_kill pthread_sigqueue \
+		      pthread_sigmask pthread_kill pthread_kill_internal \
+		      pthread_sigqueue \
 		      pthread_cancel pthread_testcancel \
 		      pthread_setcancelstate pthread_setcanceltype \
 		      pthread_once \
@@ -137,7 +139,6 @@  libpthread-routines = nptl-init nptlfreeres vars events version pt-interp \
 		      cleanup cleanup_defer cleanup_compat \
 		      cleanup_defer_compat unwind \
 		      pt-longjmp pt-cleanup\
-		      cancellation \
 		      lowlevellock \
 		      lll_timedlock_wait \
 		      pt-fork pt-fcntl \
@@ -187,8 +188,7 @@  CFLAGS-pthread_setcanceltype.c += -fexceptions -fasynchronous-unwind-tables
 
 # These are internal functions which similar functionality as setcancelstate
 # and setcanceltype.
-CFLAGS-cancellation.c += -fasynchronous-unwind-tables
-CFLAGS-libc-cancellation.c += -fasynchronous-unwind-tables
+CFLAGS-libc-cancellation.c += -fexceptions -fasynchronous-unwind-tables
 
 # Calling pthread_exit() must cause the registered cancel handlers to
 # be executed.  Therefore exceptions have to be thrown through this
@@ -286,7 +286,7 @@  tests = tst-attr2 tst-attr3 tst-default-attr \
 	tst-cancel11 tst-cancel12 tst-cancel13 tst-cancel14 tst-cancel15 \
 	tst-cancel16 tst-cancel17 tst-cancel18 tst-cancel19 tst-cancel20 \
 	tst-cancel21 tst-cancel22 tst-cancel23 tst-cancel24 \
-	tst-cancel26 tst-cancel27 tst-cancel28 \
+	tst-cancel26 tst-cancel27 tst-cancel28 tst-cancel29 \
 	tst-cancel-self tst-cancel-self-cancelstate \
 	tst-cancel-self-canceltype tst-cancel-self-testcancel \
 	tst-cleanup0 tst-cleanup1 tst-cleanup2 tst-cleanup3 tst-cleanup4 \
diff --git a/nptl/Versions b/nptl/Versions
index 543dddc4ee..41d732e1dd 100644
--- a/nptl/Versions
+++ b/nptl/Versions
@@ -41,6 +41,10 @@  libc {
     __libc_allocate_rtsig_private;
     # Used by the C11 threads implementation.
     __pthread_cond_destroy; __pthread_cond_init;
+    # Used by pthread cancellation.
+    __syscall_cancel;
+    __syscall_cancel_arch_start;
+    __syscall_cancel_arch_end;
   }
 }
 
diff --git a/nptl/cancellation.c b/nptl/cancellation.c
deleted file mode 100644
index 7127f9ae91..0000000000
--- a/nptl/cancellation.c
+++ /dev/null
@@ -1,78 +0,0 @@ 
-/* Copyright (C) 2002-2020 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-   Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library; if not, see
-   <https://www.gnu.org/licenses/>.  */
-
-#include <setjmp.h>
-#include <stdlib.h>
-#include "pthreadP.h"
-#include <futex-internal.h>
-
-
-/* The next two functions are similar to pthread_setcanceltype() but
-   more specialized for the use in the cancelable functions like write().
-   They do not need to check parameters etc.  These functions must be
-   AS-safe, with the exception of the actual cancellation, because they
-   are called by wrappers around AS-safe functions like write().*/
-int
-attribute_hidden
-__pthread_enable_asynccancel (void)
-{
-  struct pthread *self = THREAD_SELF;
-
-  int oldval = THREAD_GETMEM (self, canceltype);
-  THREAD_SETMEM (self, canceltype, PTHREAD_CANCEL_ASYNCHRONOUS);
-
-  int ch = THREAD_GETMEM (self, cancelhandling);
-
-  if (self->cancelstate == PTHREAD_CANCEL_ENABLE
-      && (ch & (CANCELED_BITMASK | EXITING_BITMASK | TERMINATED_BITMASK))
-	  == CANCELED_BITMASK)
-    {
-      THREAD_SETMEM (self, result, PTHREAD_CANCELED);
-      __do_cancel ();
-    }
-
-  return oldval;
-}
-
-/* See the comment for __pthread_enable_asynccancel regarding
-   the AS-safety of this function.  */
-void
-attribute_hidden
-__pthread_disable_asynccancel (int oldtype)
-{
-  /* If asynchronous cancellation was enabled before we do not have
-     anything to do.  */
-  if (oldtype == PTHREAD_CANCEL_ASYNCHRONOUS)
-    return;
-
-  struct pthread *self = THREAD_SELF;
-  THREAD_SETMEM (self, canceltype, PTHREAD_CANCEL_DEFERRED);
-
-  /* We cannot return when we are being canceled.  Upon return the
-     thread might be things which would have to be undone.  The
-     following loop should loop until the cancellation signal is
-     delivered.  */
-  int ch = THREAD_GETMEM (self, cancelhandling);
-  while (__glibc_unlikely ((ch & (CANCELING_BITMASK | CANCELED_BITMASK))
-			    == CANCELING_BITMASK))
-    {
-      futex_wait_simple ((unsigned int *) &self->cancelhandling, ch,
-			 FUTEX_PRIVATE);
-      ch = THREAD_GETMEM (self, cancelhandling);
-    }
-}
diff --git a/nptl/descr.h b/nptl/descr.h
index bae9457e33..c0b8f6c40e 100644
--- a/nptl/descr.h
+++ b/nptl/descr.h
@@ -269,9 +269,6 @@  struct pthread
 
   /* Flags determining processing of cancellation.  */
   int cancelhandling;
-  /* Bit set if canceling has been initiated.  */
-#define CANCELING_BIT		2
-#define CANCELING_BITMASK	(0x01 << CANCELING_BIT)
   /* Bit set if canceled.  */
 #define CANCELED_BIT		3
 #define CANCELED_BITMASK	(0x01 << CANCELED_BIT)
diff --git a/nptl/libc-cancellation.c b/nptl/libc-cancellation.c
index eae81d504c..e695d67417 100644
--- a/nptl/libc-cancellation.c
+++ b/nptl/libc-cancellation.c
@@ -18,7 +18,44 @@ 
 
 #include "pthreadP.h"
 
+/* Cancellation function called by all cancellable syscalls.  */
+long int
+__syscall_cancel (__syscall_arg_t nr, __syscall_arg_t a1,
+		  __syscall_arg_t a2, __syscall_arg_t a3,
+		  __syscall_arg_t a4, __syscall_arg_t a5,
+		  __syscall_arg_t a6)
+{
+  struct pthread *pd = THREAD_SELF;
+  long int result;
 
-#define __pthread_enable_asynccancel __libc_enable_asynccancel
-#define __pthread_disable_asynccancel __libc_disable_asynccancel
-#include <nptl/cancellation.c>
+  /* If cancellation is not enabled, call the syscall directly.  */
+  if (pd->cancelstate == PTHREAD_CANCEL_DISABLE)
+    {
+      result = INTERNAL_SYSCALL_NCS_CALL (nr, a1, a2, a3, a4, a5, a6);
+      if (INTERNAL_SYSCALL_ERROR_P (result))
+	return -INTERNAL_SYSCALL_ERRNO (result);
+      return result;
+    }
+
+  /* Call the arch-specific entry points that contains the globals markers
+     to be checked by SIGCANCEL handler.  */
+  result = __syscall_cancel_arch (&pd->cancelhandling, nr, a1, a2, a3, a4, a5,
+			          a6);
+
+  if (result == -EINTR
+      && __pthread_self_cancelled ()
+      && pd->cancelstate == PTHREAD_CANCEL_ENABLE)
+    __do_cancel (PTHREAD_CANCELED);
+
+  return result;
+}
+libc_hidden_def (__syscall_cancel)
+
+/* Since __do_cancel is a always inline function, this creates a symbol the
+   arch-specific symbol can call to cancel the thread.  */
+_Noreturn void
+attribute_hidden
+__syscall_do_cancel (void)
+{
+  __do_cancel (PTHREAD_CANCELED);
+}
diff --git a/nptl/nptl-init.c b/nptl/nptl-init.c
index 89f58d2e5e..75225965c4 100644
--- a/nptl/nptl-init.c
+++ b/nptl/nptl-init.c
@@ -39,6 +39,9 @@ 
 #include <libc-pointer-arith.h>
 #include <pthread-pids.h>
 #include <pthread_mutex_conf.h>
+#include <sigcontextinfo.h>
+#include <cancellation-sigmask.h>
+#include <cancellation-pc-check.h>
 
 #ifndef TLS_MULTIPLE_THREADS_IN_TCB
 /* Pointer to the corresponding variable in libc.  */
@@ -137,35 +140,23 @@  sigcancel_handler (int sig, siginfo_t *si, void *ctx)
 
   struct pthread *self = THREAD_SELF;
 
-  int oldval = THREAD_GETMEM (self, cancelhandling);
-  while (1)
-    {
-      /* We are canceled now.  When canceled by another thread this flag
-	 is already set but if the signal is directly send (internally or
-	 from another process) is has to be done here.  */
-      int newval = oldval | CANCELING_BITMASK | CANCELED_BITMASK;
-
-      if (oldval == newval || (oldval & EXITING_BITMASK) != 0)
-	/* Already canceled or exiting.  */
-	break;
-
-      int curval = THREAD_ATOMIC_CMPXCHG_VAL (self, cancelhandling, newval,
-					      oldval);
-      if (curval == oldval)
-	{
-	  /* Set the return value.  */
-	  THREAD_SETMEM (self, result, PTHREAD_CANCELED);
-
-	  /* Make sure asynchronous cancellation is still enabled.  */
-	  if (self->canceltype == PTHREAD_CANCEL_ASYNCHRONOUS)
-	    /* Run the registered destructors and terminate the thread.  */
-	    __do_cancel ();
-
-	  break;
-	}
-
-      oldval = curval;
-    }
+  if (!__pthread_self_cancelled ()
+      || self->cancelstate == PTHREAD_CANCEL_DISABLE)
+    return;
+
+  /* Add SIGCANCEL on ignored sigmask to avoid the handler to be called
+     again.  */
+  ucontext_block_sigcancel (ctx);
+
+  /* Check if asynchronous cancellation mode is set or if interrupted
+     instruction pointer falls within the cancellable syscall bridge.  For
+     interruptable syscalls that might generate external side-effects (partial
+     reads or writes, for instance), the kernel will set the IP to after
+     '__syscall_cancel_arch_end', thus disabling the cancellation and allowing
+     the process to handle such conditions.  */
+  if (self->canceltype == PTHREAD_CANCEL_ASYNCHRONOUS
+      || cancellation_pc_check (ctx))
+    __do_cancel (PTHREAD_CANCELED);
 }
 
 
@@ -260,28 +251,39 @@  __pthread_initialize_minimal_internal (void)
      had to set __nptl_initial_report_events.  Propagate its setting.  */
   THREAD_SETMEM (pd, report_events, __nptl_initial_report_events);
 
-  struct sigaction sa;
-  __sigemptyset (&sa.sa_mask);
-
   /* Install the cancellation signal handler.  If for some reason we
      cannot install the handler we do not abort.  Maybe we should, but
      it is only asynchronous cancellation which is affected.  */
-  sa.sa_sigaction = sigcancel_handler;
-  sa.sa_flags = SA_SIGINFO;
-  (void) __libc_sigaction (SIGCANCEL, &sa, NULL);
+  {
+    struct sigaction sa;
+    sa.sa_sigaction = sigcancel_handler;
+    /* The signal handle should be non-interruptible to avoid the risk of
+       spurious EINTR caused by SIGCANCEL sent to process or if pthread_cancel
+       is called while cancellation is disabled in the target thread.  */
+    sa.sa_flags = SA_SIGINFO | SA_RESTART;
+    sa.sa_mask = sigall_set;
+    __libc_sigaction (SIGCANCEL, &sa, NULL);
+  }
 
-  /* Install the handle to change the threads' uid/gid.  */
-  sa.sa_sigaction = sighandler_setxid;
-  sa.sa_flags = SA_SIGINFO | SA_RESTART;
-  (void) __libc_sigaction (SIGSETXID, &sa, NULL);
+  {
+    /* Install the handle to change the threads' uid/gid.  */
+    struct sigaction sa;
+    __sigemptyset (&sa.sa_mask);
+    sa.sa_sigaction = sighandler_setxid;
+    sa.sa_flags = SA_SIGINFO | SA_RESTART;
+    __libc_sigaction (SIGSETXID, &sa, NULL);
+  }
 
   /* The parent process might have left the signals blocked.  Just in
-     case, unblock it.  We reuse the signal mask in the sigaction
-     structure.  It is already cleared.  */
-  __sigaddset (&sa.sa_mask, SIGCANCEL);
-  __sigaddset (&sa.sa_mask, SIGSETXID);
-  INTERNAL_SYSCALL_CALL (rt_sigprocmask, SIG_UNBLOCK, &sa.sa_mask,
-			 NULL, _NSIG / 8);
+     case, unblock it.  */
+  {
+    struct sigaction sa;
+    __sigemptyset (&sa.sa_mask);
+    __sigaddset (&sa.sa_mask, SIGCANCEL);
+    __sigaddset (&sa.sa_mask, SIGSETXID);
+    INTERNAL_SYSCALL_CALL (rt_sigprocmask, SIG_UNBLOCK, &sa.sa_mask,
+			   NULL, _NSIG / 8);
+  }
 
   /* Get the size of the static and alignment requirements for the TLS
      block.  */
diff --git a/nptl/pthreadP.h b/nptl/pthreadP.h
index d55c3b26a4..a20b136f14 100644
--- a/nptl/pthreadP.h
+++ b/nptl/pthreadP.h
@@ -286,20 +286,13 @@  extern void __nptl_unwind_freeres (void) attribute_hidden;
 #endif
 
 
-/* Called when a thread reacts on a cancellation request.  */
-static inline void
-__attribute ((noreturn, always_inline))
-__do_cancel (void)
-{
-  struct pthread *self = THREAD_SELF;
-
-  /* Make sure we get no more cancellations.  */
-  THREAD_ATOMIC_BIT_SET (self, cancelhandling, EXITING_BIT);
-
-  __pthread_unwind ((__pthread_unwind_buf_t *)
-		    THREAD_GETMEM (self, cleanup_jmp_buf));
-}
+extern long int __syscall_cancel_arch (volatile int *, __syscall_arg_t nr,
+     __syscall_arg_t arg1, __syscall_arg_t arg2, __syscall_arg_t arg3,
+     __syscall_arg_t arg4, __syscall_arg_t arg5, __syscall_arg_t arg6);
+libc_hidden_proto (__syscall_cancel_arch);
 
+extern _Noreturn void __syscall_do_cancel (void)
+     attribute_hidden;
 
 /* Internal prototypes.  */
 
@@ -461,12 +454,13 @@  extern int __pthread_equal (pthread_t thread1, pthread_t thread2);
 extern int __pthread_detach (pthread_t th);
 extern int __pthread_cancel (pthread_t th);
 extern int __pthread_kill (pthread_t threadid, int signo);
-extern void __pthread_exit (void *value) __attribute__ ((__noreturn__));
+extern int __pthread_kill_internal (pthread_t threadid, int signo)
+  attribute_hidden;
+extern void _Noreturn __pthread_exit (void *value);
 extern int __pthread_join (pthread_t threadid, void **thread_return);
 extern int __pthread_setcanceltype (int type, int *oldtype);
-extern int __pthread_enable_asynccancel (void) attribute_hidden;
-extern void __pthread_disable_asynccancel (int oldtype) attribute_hidden;
 extern void __pthread_testcancel (void);
+extern void __pthread_exit (void *value);
 extern int __pthread_clockjoin_ex (pthread_t, void **, clockid_t,
 				   const struct timespec *, bool)
   attribute_hidden;
@@ -487,10 +481,41 @@  hidden_proto (__pthread_setspecific)
 hidden_proto (__pthread_once)
 hidden_proto (__pthread_setcancelstate)
 hidden_proto (__pthread_testcancel)
+hidden_proto (__pthread_exit)
 hidden_proto (__pthread_mutexattr_init)
 hidden_proto (__pthread_mutexattr_settype)
 #endif
 
+/* Called when a thread reacts on a cancellation request.  */
+_Noreturn static inline void
+__do_cancel (void *value)
+{
+  struct pthread *self = THREAD_SELF;
+
+  /* Make sure we get no more cancellations by clearing the cancel
+     state.  */
+  THREAD_SETMEM (self, cancelstate, PTHREAD_CANCEL_DISABLE);
+  THREAD_SETMEM (self, canceltype, PTHREAD_CANCEL_DEFERRED);
+
+  THREAD_SETMEM (self, result, value);
+
+  THREAD_ATOMIC_BIT_SET (self, cancelhandling, EXITING_BIT);
+
+  __pthread_unwind ((__pthread_unwind_buf_t *)
+		    THREAD_GETMEM (self, cleanup_jmp_buf));
+}
+
+static inline bool
+__pthread_self_cancelled (void)
+{
+  struct pthread *self = THREAD_SELF;
+  int cancelhandling = THREAD_GETMEM (self, cancelhandling);
+  return self->cancelstate == PTHREAD_CANCEL_ENABLE
+	  && (cancelhandling & (CANCELED_BITMASK | EXITING_BITMASK
+			        | TERMINATED_BITMASK))
+	      == CANCELED_BITMASK;
+}
+
 extern int __pthread_cond_broadcast_2_0 (pthread_cond_2_0_t *cond);
 extern int __pthread_cond_destroy_2_0 (pthread_cond_2_0_t *cond);
 extern int __pthread_cond_init_2_0 (pthread_cond_2_0_t *cond,
diff --git a/nptl/pthread_cancel.c b/nptl/pthread_cancel.c
index 7518c0b8bf..3873a47af8 100644
--- a/nptl/pthread_cancel.c
+++ b/nptl/pthread_cancel.c
@@ -37,63 +37,29 @@  __pthread_cancel (pthread_t th)
 #ifdef SHARED
   pthread_cancel_init ();
 #endif
-  int result = 0;
-  int oldval;
-  int newval;
-  do
-    {
-    again:
-      oldval = pd->cancelhandling;
-      newval = oldval | CANCELING_BITMASK | CANCELED_BITMASK;
-
-      /* Avoid doing unnecessary work.  The atomic operation can
-	 potentially be expensive if the bug has to be locked and
-	 remote cache lines have to be invalidated.  */
-      if (oldval == newval)
-	break;
-
-      /* If the cancellation is handled asynchronously just send a
-	 signal.  We avoid this if possible since it's more
-	 expensive.  */
-      if (pd->cancelstate == PTHREAD_CANCEL_ENABLE
-	  && pd->canceltype == PTHREAD_CANCEL_ASYNCHRONOUS
-	  && (newval & (CANCELED_BITMASK | EXITING_BITMASK
-			| TERMINATED_BITMASK))
-	      == CANCELED_BITMASK)
-	{
-	  /* Mark the cancellation as "in progress".  */
-	  if (atomic_compare_and_exchange_bool_acq (&pd->cancelhandling,
-						    oldval | CANCELING_BITMASK,
-						    oldval))
-	    goto again;
 
-	  /* The cancellation handler will take care of marking the
-	     thread as canceled.  */
-	  pid_t pid = __getpid ();
+  THREAD_ATOMIC_BIT_SET (pd, cancelhandling, CANCELED_BIT);
 
-	  int val = INTERNAL_SYSCALL_CALL (tgkill, pid, pd->tid,
-					   SIGCANCEL);
-	  if (INTERNAL_SYSCALL_ERROR_P (val))
-	    result = INTERNAL_SYSCALL_ERRNO (val);
+  /* A single-threaded process should be able to kill itself, since there is
+     nothing in the POSIX specification that says that it cannot.  So we set
+     multiple_threads to true so that cancellation points get executed.  */
+  THREAD_SETMEM (THREAD_SELF, header.multiple_threads, 1);
 
-	  break;
-	}
-
-	/* A single-threaded process should be able to kill itself, since
-	   there is nothing in the POSIX specification that says that it
-	   cannot.  So we set multiple_threads to true so that cancellation
-	   points get executed.  */
-	THREAD_SETMEM (THREAD_SELF, header.multiple_threads, 1);
 #ifndef TLS_MULTIPLE_THREADS_IN_TCB
-	__pthread_multiple_threads = *__libc_multiple_threads_ptr = 1;
+  __pthread_multiple_threads = *__libc_multiple_threads_ptr = 1;
 #endif
+
+  /* Avoid signaling when thread attempts cancel itself (pthread_kill
+     is expensive).  */
+  if (pd == THREAD_SELF)
+    {
+      if (pd->cancelstate == PTHREAD_CANCEL_ENABLE
+	  && pd->canceltype == PTHREAD_CANCEL_ASYNCHRONOUS)
+	__pthread_exit (PTHREAD_CANCELED);
+      return 0;
     }
-  /* Mark the thread as canceled.  This has to be done
-     atomically since other bits could be modified as well.  */
-  while (atomic_compare_and_exchange_bool_acq (&pd->cancelhandling, newval,
-					       oldval));
 
-  return result;
+  return __pthread_kill_internal (th, SIGCANCEL);
 }
 weak_alias (__pthread_cancel, pthread_cancel)
 
diff --git a/nptl/pthread_create.c b/nptl/pthread_create.c
index 7c752d0f99..bc9dd2d965 100644
--- a/nptl/pthread_create.c
+++ b/nptl/pthread_create.c
@@ -402,7 +402,7 @@  START_THREAD_DEFN
   /* If the parent was running cancellation handlers while creating
      the thread the new thread inherited the signal mask.  Reset the
      cancellation signal mask.  */
-  if (__glibc_unlikely (pd->parent_cancelhandling & CANCELING_BITMASK))
+  if (__glibc_unlikely (pd->parent_cancelhandling & CANCELED_BITMASK))
     {
       sigset_t mask;
       __sigemptyset (&mask);
@@ -443,7 +443,8 @@  START_THREAD_DEFN
 	 have ownership (see CONCURRENCY NOTES above).  */
       if (__glibc_unlikely (pd->stopped_start))
 	{
-	  int oldtype = CANCEL_ASYNC ();
+	  int ct;
+	  __pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, &ct);
 
 	  /* Get the lock the parent locked to force synchronization.  */
 	  lll_lock (pd->lock, LLL_PRIVATE);
@@ -453,7 +454,7 @@  START_THREAD_DEFN
 	  /* And give it up right away.  */
 	  lll_unlock (pd->lock, LLL_PRIVATE);
 
-	  CANCEL_RESET (oldtype);
+	  __pthread_setcanceltype (ct, NULL);
 	}
 
       LIBC_PROBE (pthread_start, 3, (pthread_t) pd, pd->start_routine, pd->arg);
diff --git a/nptl/pthread_exit.c b/nptl/pthread_exit.c
index e9b5e62c86..059b30623d 100644
--- a/nptl/pthread_exit.c
+++ b/nptl/pthread_exit.c
@@ -16,18 +16,15 @@ 
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
-#include <stdlib.h>
 #include "pthreadP.h"
 
-
-void
+_Noreturn void
 __pthread_exit (void *value)
 {
-  THREAD_SETMEM (THREAD_SELF, result, value);
-
-  __do_cancel ();
+  __do_cancel (value);
 }
 weak_alias (__pthread_exit, pthread_exit)
+hidden_def (__pthread_exit)
 
 /* After a thread terminates, __libc_start_main decrements
    __nptl_nthreads defined in pthread_create.c.  */
diff --git a/nptl/pthread_join_common.c b/nptl/pthread_join_common.c
index 03e202136f..4d1898c52b 100644
--- a/nptl/pthread_join_common.c
+++ b/nptl/pthread_join_common.c
@@ -70,7 +70,8 @@  clockwait_tid (pid_t *tidp, clockid_t clockid, const struct timespec *abstime)
       /* If *tidp == tid, wait until thread terminates or the wait times out.
          The kernel up to version 3.16.3 does not use the private futex
          operations for futex wake-up when the clone terminates.  */
-      if (lll_futex_timed_wait_cancel (tidp, tid, &rt, LLL_SHARED)
+      if (lll_futex_timed_wait_cancel ((unsigned int *) tidp, tid, &rt,
+				       LLL_SHARED)
 	  == -ETIMEDOUT)
         return ETIMEDOUT;
     }
@@ -103,7 +104,7 @@  __pthread_clockjoin_ex (pthread_t threadid, void **thread_return,
   if ((pd == self
        || (self->joinid == pd
 	   && (pd->cancelhandling
-	       & (CANCELING_BITMASK | CANCELED_BITMASK | EXITING_BITMASK
+	       & (CANCELED_BITMASK | EXITING_BITMASK
 		  | TERMINATED_BITMASK)) == 0))
       && !(self->cancelstate == PTHREAD_CANCEL_ENABLE
 	   && (pd->cancelhandling & (CANCELED_BITMASK | EXITING_BITMASK
@@ -145,7 +146,7 @@  __pthread_clockjoin_ex (pthread_t threadid, void **thread_return,
 	  /* We need acquire MO here so that we synchronize with the
 	     kernel's store to 0 when the clone terminates. (see above)  */
 	  while ((tid = atomic_load_acquire (&pd->tid)) != 0)
-	    lll_futex_wait_cancel (&pd->tid, tid, LLL_SHARED);
+	    lll_futex_wait_cancel ((unsigned int *) &pd->tid, tid, LLL_SHARED);
 	}
 
       pthread_cleanup_pop (0);
diff --git a/nptl/pthread_kill.c b/nptl/pthread_kill.c
index 73144a07ec..bf9e9bb81f 100644
--- a/nptl/pthread_kill.c
+++ b/nptl/pthread_kill.c
@@ -31,8 +31,9 @@  __pthread_kill (pthread_t threadid, int signo)
     /* Not a valid thread handle.  */
     return ESRCH;
 
-  return ENOSYS;
+  if (__is_internal_signal (signo))
+    return EINVAL;
+
+  return __pthread_kill_internal (threadid, signo);
 }
 strong_alias (__pthread_kill, pthread_kill)
-
-stub_warning (pthread_kill)
diff --git a/sysdeps/unix/sysv/linux/pthread_kill.c b/nptl/pthread_kill_internal.c
similarity index 75%
rename from sysdeps/unix/sysv/linux/pthread_kill.c
rename to nptl/pthread_kill_internal.c
index 4dfe08ffcd..f428a46f57 100644
--- a/sysdeps/unix/sysv/linux/pthread_kill.c
+++ b/nptl/pthread_kill_internal.c
@@ -16,24 +16,15 @@ 
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
-#include <errno.h>
-#include <signal.h>
-#include <pthreadP.h>
-#include <tls.h>
-#include <sysdep.h>
 #include <unistd.h>
+#include <pthreadP.h>
 
-
+/* Used internally by pthread_cancel, so we can't filter SIGCANCEL.  */
 int
-__pthread_kill (pthread_t threadid, int signo)
+__pthread_kill_internal (pthread_t threadid, int signo)
 {
   struct pthread *pd = (struct pthread *) threadid;
 
-  /* Make sure the descriptor is valid.  */
-  if (DEBUGGING_P && INVALID_TD_P (pd))
-    /* Not a valid thread handle.  */
-    return ESRCH;
-
   /* Force load of pd->tid into local variable or register.  Otherwise
      if a thread exits between ESRCH test and tgkill, we might return
      EINVAL, because pd->tid would be cleared by the kernel.  */
@@ -42,11 +33,6 @@  __pthread_kill (pthread_t threadid, int signo)
     /* Not a valid thread handle.  */
     return ESRCH;
 
-  /* Disallow sending the signal we use for cancellation, timers,
-     for the setxid implementation.  */
-  if (signo == SIGCANCEL || signo == SIGTIMER || signo == SIGSETXID)
-    return EINVAL;
-
   /* We have a special syscall to do the work.  */
   pid_t pid = __getpid ();
 
@@ -54,4 +40,3 @@  __pthread_kill (pthread_t threadid, int signo)
   return (INTERNAL_SYSCALL_ERROR_P (val)
 	  ? INTERNAL_SYSCALL_ERRNO (val) : 0);
 }
-strong_alias (__pthread_kill, pthread_kill)
diff --git a/nptl/pthread_setcanceltype.c b/nptl/pthread_setcanceltype.c
index d8cb54736d..77e4adf537 100644
--- a/nptl/pthread_setcanceltype.c
+++ b/nptl/pthread_setcanceltype.c
@@ -37,4 +37,4 @@  __pthread_setcanceltype (int type, int *oldtype)
 
   return 0;
 }
-strong_alias (__pthread_setcanceltype, pthread_setcanceltype)
+weak_alias (__pthread_setcanceltype, pthread_setcanceltype)
diff --git a/nptl/pthread_testcancel.c b/nptl/pthread_testcancel.c
index 026c20f82e..584ff242be 100644
--- a/nptl/pthread_testcancel.c
+++ b/nptl/pthread_testcancel.c
@@ -23,16 +23,8 @@ 
 void
 __pthread_testcancel (void)
 {
-  struct pthread *self = THREAD_SELF;
-  int cancelhandling = THREAD_GETMEM (self, cancelhandling);
-  if (self->cancelstate == PTHREAD_CANCEL_ENABLE
-      && (cancelhandling & (CANCELED_BITMASK | EXITING_BITMASK
-			    | TERMINATED_BITMASK))
-	  == CANCELED_BITMASK)
-    {
-      THREAD_SETMEM (self, result, PTHREAD_CANCELED);
-      __do_cancel ();
-    }
+  if (__pthread_self_cancelled ())
+    __do_cancel (PTHREAD_CANCELED);
 }
 weak_alias (__pthread_testcancel, pthread_testcancel)
 hidden_def (__pthread_testcancel)
diff --git a/nptl/sem_wait.c b/nptl/sem_wait.c
index 171716fdbc..1ba9926c0e 100644
--- a/nptl/sem_wait.c
+++ b/nptl/sem_wait.c
@@ -58,7 +58,7 @@  __old_sem_wait (sem_t *sem)
 	return 0;
 
       /* Always assume the semaphore is shared.  */
-      err = lll_futex_wait_cancel (futex, 0, LLL_SHARED);
+      err = lll_futex_wait_cancel ((unsigned int *) futex, 0, LLL_SHARED);
     }
   while (err == 0 || err == -EWOULDBLOCK);
 
diff --git a/nptl/tst-cancel29.c b/nptl/tst-cancel29.c
new file mode 100644
index 0000000000..1671cfe04f
--- /dev/null
+++ b/nptl/tst-cancel29.c
@@ -0,0 +1,100 @@ 
+/* Check side-effect act for cancellable syscalls (BZ #12683).
+   Copyright (C) 2020 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+/* This testcase checks if there is resource leakage if the syscall has
+   returned from kernelspace, but before userspace saves the return
+   value.  The 'leaker' thread should be able to close the file descriptor
+   if the resource is already allocated, meaning that if the cancellation
+   signal arrives *after* the open syscal return from kernel, the
+   side-effect should be visible to application.  */
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <stdlib.h>
+
+#include <support/xunistd.h>
+#include <support/xthread.h>
+#include <support/check.h>
+#include <support/temp_file.h>
+#include <support/support.h>
+#include <support/descriptors.h>
+
+static void *
+writeopener (void *arg)
+{
+  int fd;
+  for (;;)
+    {
+      fd = open (arg, O_WRONLY);
+      xclose (fd);
+    }
+  return NULL;
+}
+
+static void *
+leaker (void *arg)
+{
+  int fd = open (arg, O_RDONLY);
+  TEST_VERIFY_EXIT (fd > 0);
+  pthread_setcancelstate (PTHREAD_CANCEL_DISABLE, 0);
+  xclose (fd);
+  return NULL;
+}
+
+static int
+do_test (void)
+{
+  enum {
+    iter_count = 1000
+  };
+
+  char *dir = support_create_temp_directory ("tst-cancel28");
+  char *name = xasprintf ("%s/fifo", dir);
+  TEST_COMPARE (mkfifo (name, 0600), 0);
+  add_temp_file (name);
+
+  struct support_descriptors *descrs = support_descriptors_list ();
+
+  srand (1);
+
+  xpthread_create (NULL, writeopener, name);
+  for (int i = 0; i < iter_count; i++)
+    {
+      pthread_t td = xpthread_create (NULL, leaker, name);
+      struct timespec ts =
+	{ .tv_nsec = rand () % 100000, .tv_sec = 0 };
+      nanosleep (&ts, NULL);
+      /* Ignore pthread_cancel result because it might be the
+	 case when pthread_cancel is called when thread is already
+	 exited.  */
+      pthread_cancel (td);
+      xpthread_join (td);
+    }
+
+  support_descriptors_check (descrs);
+
+  support_descriptors_free (descrs);
+
+  free (name);
+
+  return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/rt/Makefile b/rt/Makefile
index dab5d62a57..565b76c9c4 100644
--- a/rt/Makefile
+++ b/rt/Makefile
@@ -57,7 +57,7 @@  include ../Rules
 CFLAGS-aio_suspend.c += -fexceptions
 CFLAGS-mq_timedreceive.c += -fexceptions -fasynchronous-unwind-tables
 CFLAGS-mq_timedsend.c += -fexceptions -fasynchronous-unwind-tables
-CFLAGS-librt-cancellation.c += -fasynchronous-unwind-tables
+CFLAGS-clock_nanosleep.c += -fexceptions -fasynchronous-unwind-tables
 
 LDFLAGS-rt.so = -Wl,--enable-new-dtags,-z,nodelete
 
diff --git a/sysdeps/nptl/librt-cancellation.c b/sysdeps/generic/syscall_types.h
similarity index 70%
rename from sysdeps/nptl/librt-cancellation.c
rename to sysdeps/generic/syscall_types.h
index af1d11b2e6..cf11956fd7 100644
--- a/sysdeps/nptl/librt-cancellation.c
+++ b/sysdeps/generic/syscall_types.h
@@ -1,6 +1,6 @@ 
-/* Copyright (C) 2002-2020 Free Software Foundation, Inc.
+/* Types and macros used for syscall issuing.
+   Copyright (C) 2020 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
-   Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
 
    The GNU C Library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
@@ -16,9 +16,10 @@ 
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
-#include <nptl/pthreadP.h>
+#ifndef _SYSCALL_TYPES_H
+#define _SYSCALL_TYPES_H
 
+typedef long int __syscall_arg_t;
+#define __SSC(__x) ((__syscall_arg_t) (__x))
 
-#define __pthread_enable_asynccancel __librt_enable_asynccancel
-#define __pthread_disable_asynccancel __librt_disable_asynccancel
-#include <nptl/cancellation.c>
+#endif
diff --git a/sysdeps/generic/sysdep-cancel.h b/sysdeps/generic/sysdep-cancel.h
index d22a786536..5c84b4499a 100644
--- a/sysdeps/generic/sysdep-cancel.h
+++ b/sysdeps/generic/sysdep-cancel.h
@@ -3,5 +3,3 @@ 
 /* No multi-thread handling enabled.  */
 #define SINGLE_THREAD_P (1)
 #define RTLD_SINGLE_THREAD_P (1)
-#define LIBC_CANCEL_ASYNC()	0 /* Just a dummy value.  */
-#define LIBC_CANCEL_RESET(val)	((void)(val)) /* Nothing, but evaluate it.  */
diff --git a/sysdeps/nptl/Makefile b/sysdeps/nptl/Makefile
index 0631a870c8..30f9c8e91e 100644
--- a/sysdeps/nptl/Makefile
+++ b/sysdeps/nptl/Makefile
@@ -21,8 +21,7 @@  libpthread-sysdep_routines += errno-loc
 endif
 
 ifeq ($(subdir),rt)
-librt-sysdep_routines += timer_routines librt-cancellation
-CFLAGS-librt-cancellation.c += -fexceptions -fasynchronous-unwind-tables
+librt-sysdep_routines += timer_routines
 
 tests += tst-mqueue8x
 CFLAGS-tst-mqueue8x.c += -fexceptions
diff --git a/sysdeps/nptl/cancellation-pc-check.h b/sysdeps/nptl/cancellation-pc-check.h
new file mode 100644
index 0000000000..ae124fcced
--- /dev/null
+++ b/sysdeps/nptl/cancellation-pc-check.h
@@ -0,0 +1,53 @@ 
+/* Architecture specific code for pthread cancellation handling.
+   Copyright (C) 2020 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef _NPTL_CANCELLATION_PC_CHECK
+#define _NPTL_CANCELLATION_PC_CHECK
+
+#include <sigcontextinfo.h>
+
+/* For syscalls with side-effects, the kernel cannot restart the syscall; when
+   it is interrupted by a signal, the kernel must cause the syscall to return
+   with whatever partial result is obtained (e.g. partial read or write).  In
+   this case, the saved program counter points just after the syscall
+   instruction, so the SIGCANCEL handler should not act on cancellation.
+
+   The __syscall_cancel_arch function, used for all cancellable syscalls,
+   contains two extra markers, __syscall_cancel_arch_start and
+   __syscall_cancel_arch_end.  The former points to just before the initial
+   conditional branch that checks if the thread has received a cancellation
+   request, while former points to the instruction after the one responsible
+   to issue the syscall.
+
+   The function check if the program counter (PC) from ucontext_t CTX is
+   within the start and then end boundary from the __syscall_cancel_arch
+   bridge.  Return TRUE if the PC is within the boundary, meaning the
+   syscall does not have any side effects; or FALSE otherwise.  */
+static bool
+cancellation_pc_check (void *ctx)
+{
+  /* Both are defined in syscall_cancel.S.  */
+  extern const char __syscall_cancel_arch_start[1];
+  extern const char __syscall_cancel_arch_end[1];
+
+  uintptr_t pc = sigcontext_get_pc (ctx);
+  return pc >= (uintptr_t) __syscall_cancel_arch_start
+	 && pc < (uintptr_t) __syscall_cancel_arch_end;
+}
+
+#endif
diff --git a/sysdeps/nptl/cancellation-sigmask.h b/sysdeps/nptl/cancellation-sigmask.h
new file mode 100644
index 0000000000..80c2a2d2f2
--- /dev/null
+++ b/sysdeps/nptl/cancellation-sigmask.h
@@ -0,0 +1,30 @@ 
+/* Architecture specific code for pthread cancellation handling.
+   Copyright (C) 2020 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef _NPTL_CANCELLATION_SIGMASK_H
+#define _NPTL_CANCELLATION_SIGMASK_H
+
+/* Add the SIGCANCEL signal on sigmask set at the ucontext_t CTX obtained from
+   the sigaction handler.  */
+static void
+ucontext_block_sigcancel (void *ctx)
+{
+  __sigaddset (&((ucontext_t*) ctx)->uc_sigmask, SIGCANCEL);
+}
+
+#endif
diff --git a/sysdeps/nptl/futex-internal.h b/sysdeps/nptl/futex-internal.h
index d622122ddc..9bce768afc 100644
--- a/sysdeps/nptl/futex-internal.h
+++ b/sysdeps/nptl/futex-internal.h
@@ -178,10 +178,7 @@  static __always_inline int
 futex_wait_cancelable (unsigned int *futex_word, unsigned int expected,
 		       int private)
 {
-  int oldtype;
-  oldtype = __pthread_enable_asynccancel ();
-  int err = lll_futex_timed_wait (futex_word, expected, NULL, private);
-  __pthread_disable_asynccancel (oldtype);
+  int err = lll_futex_timed_wait_cancel (futex_word, expected, NULL, private);
   switch (err)
     {
     case 0:
@@ -239,10 +236,8 @@  futex_reltimed_wait_cancelable (unsigned int* futex_word,
 				unsigned int expected,
 			        const struct timespec* reltime, int private)
 {
-  int oldtype;
-  oldtype = LIBC_CANCEL_ASYNC ();
-  int err = lll_futex_timed_wait (futex_word, expected, reltime, private);
-  LIBC_CANCEL_RESET (oldtype);
+  int err = lll_futex_timed_wait_cancel (futex_word, expected, reltime,
+					 private);
   switch (err)
     {
     case 0:
@@ -315,12 +310,8 @@  futex_abstimed_wait_cancelable (unsigned int* futex_word,
      despite them being valid.  */
   if (__glibc_unlikely ((abstime != NULL) && (abstime->tv_sec < 0)))
     return ETIMEDOUT;
-  int oldtype;
-  oldtype = __pthread_enable_asynccancel ();
-  int err = lll_futex_clock_wait_bitset (futex_word, expected,
-					clockid, abstime,
-					private);
-  __pthread_disable_asynccancel (oldtype);
+  int err = lll_futex_clock_wait_bitset_cancel (futex_word, expected, clockid,
+						abstime, private);
   switch (err)
     {
     case 0:
diff --git a/sysdeps/nptl/lowlevellock-futex.h b/sysdeps/nptl/lowlevellock-futex.h
index 2209ca76a1..4b72deda95 100644
--- a/sysdeps/nptl/lowlevellock-futex.h
+++ b/sysdeps/nptl/lowlevellock-futex.h
@@ -174,21 +174,36 @@ 
 		     nr_wake, nr_move, mutex, val)
 
 /* Like lll_futex_wait, but acting as a cancellable entrypoint.  */
-# define lll_futex_wait_cancel(futexp, val, private) \
-  ({                                                                   \
-    int __oldtype = CANCEL_ASYNC ();				       \
-    long int __err = lll_futex_wait (futexp, val, LLL_SHARED);	       \
-    CANCEL_RESET (__oldtype);					       \
-    __err;							       \
-  })
+# define lll_futex_wait_cancel(futexp, val, private)			\
+  lll_futex_timed_wait_cancel (futexp, val, NULL, private)
 
 /* Like lll_futex_timed_wait, but acting as a cancellable entrypoint.  */
-# define lll_futex_timed_wait_cancel(futexp, val, timeout, private) \
-  ({									   \
-    int __oldtype = CANCEL_ASYNC ();				       	   \
-    long int __err = lll_futex_timed_wait (futexp, val, timeout, private); \
-    CANCEL_RESET (__oldtype);						   \
-    __err;								   \
+# define lll_futex_timed_wait_cancel(futexp, val, timeout, private) 	\
+  ({									\
+     int __op = __lll_private_flag (FUTEX_WAIT, private);		\
+     INTERNAL_SYSCALL_CANCEL (futex, futexp, __op, val, timeout);	\
+  })
+
+/* Like lll_futex_clock_wait_bitset, but acting as a cancellable
+   entrypoint.  */
+# define lll_futex_clock_wait_bitset_cancel(futexp, val, clockid, timeout, \
+					    private)			   \
+  ({									\
+    long int __ret;							\
+    if (lll_futex_supported_clockid (clockid))			  	\
+      {								 	\
+	const unsigned int __clockbit =				 	\
+	  (clockid == CLOCK_REALTIME) ? FUTEX_CLOCK_REALTIME : 0;       \
+	const int __op =						\
+	  __lll_private_flag (FUTEX_WAIT_BITSET | __clockbit, private); \
+									\
+	__ret = INTERNAL_SYSCALL_CANCEL (futex, futexp, __op, val,	\
+					 timeout, NULL,			\
+					 FUTEX_BITSET_MATCH_ANY);	\
+      }								 	\
+    else								\
+      __ret = -EINVAL;							\
+    __ret;								\
   })
 
 #endif  /* !__ASSEMBLER__  */
diff --git a/sysdeps/unix/sysdep.h b/sysdeps/unix/sysdep.h
index 3c687a717a..c19cffabee 100644
--- a/sysdeps/unix/sysdep.h
+++ b/sysdeps/unix/sysdep.h
@@ -15,6 +15,9 @@ 
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
+#ifndef _SYSDEP_UNIX_H
+#define _SYSDEP_UNIX_H 1
+
 #include <sysdeps/generic/sysdep.h>
 #include <single-thread.h>
 #include <sys/syscall.h>
@@ -24,6 +27,9 @@ 
 #define	SYSCALL__(name, args)	PSEUDO (__##name, name, args)
 #define	SYSCALL(name, args)	PSEUDO (name, name, args)
 
+#ifndef __ASSEMBLER__
+# include <errno.h>
+
 #define __SYSCALL_CONCAT_X(a,b)     a##b
 #define __SYSCALL_CONCAT(a,b)       __SYSCALL_CONCAT_X (a, b)
 
@@ -57,6 +63,29 @@ 
 #define INTERNAL_SYSCALL_CALL(...) \
   __INTERNAL_SYSCALL_DISP (__INTERNAL_SYSCALL, __VA_ARGS__)
 
+#define __INTERNAL_SYSCALL_NCS0(name) \
+  INTERNAL_SYSCALL_NCS (name, 0)
+#define __INTERNAL_SYSCALL_NCS1(name, a1) \
+  INTERNAL_SYSCALL_NCS (name, 1, a1)
+#define __INTERNAL_SYSCALL_NCS2(name, a1, a2) \
+  INTERNAL_SYSCALL_NCS (name, 2, a1, a2)
+#define __INTERNAL_SYSCALL_NCS3(name, a1, a2, a3) \
+  INTERNAL_SYSCALL_NCS (name, 3, a1, a2, a3)
+#define __INTERNAL_SYSCALL_NCS4(name, a1, a2, a3, a4) \
+  INTERNAL_SYSCALL_NCS (name, 4, a1, a2, a3, a4)
+#define __INTERNAL_SYSCALL_NCS5(name, a1, a2, a3, a4, a5) \
+  INTERNAL_SYSCALL_NCS (name, 5, a1, a2, a3, a4, a5)
+#define __INTERNAL_SYSCALL_NCS6(name, a1, a2, a3, a4, a5, a6) \
+  INTERNAL_SYSCALL_NCS (name, 6, a1, a2, a3, a4, a5, a6)
+#define __INTERNAL_SYSCALL_NCS7(name, a1, a2, a3, a4, a5, a6, a7) \
+  INTERNAL_SYSCALL_NCS (name, 7, a1, a2, a3, a4, a5, a6, a7)
+
+/* Issue a syscall defined by syscall number plus any other argument required.
+   It is similar to INTERNAL_SYSCALL_NCS macro, but without the need to pass
+   the expected argument number as third parameter.  */
+#define INTERNAL_SYSCALL_NCS_CALL(...) \
+  __INTERNAL_SYSCALL_DISP (__INTERNAL_SYSCALL_NCS, __VA_ARGS__)
+
 #define __INLINE_SYSCALL0(name) \
   INLINE_SYSCALL (name, 0)
 #define __INLINE_SYSCALL1(name, a1) \
@@ -88,35 +117,68 @@ 
 #define INLINE_SYSCALL_CALL(...) \
   __INLINE_SYSCALL_DISP (__INLINE_SYSCALL, __VA_ARGS__)
 
-#define SYSCALL_CANCEL(...) \
-  ({									     \
-    long int sc_ret;							     \
-    if (SINGLE_THREAD_P) 						     \
-      sc_ret = INLINE_SYSCALL_CALL (__VA_ARGS__); 			     \
-    else								     \
-      {									     \
-	int sc_cancel_oldtype = LIBC_CANCEL_ASYNC ();			     \
-	sc_ret = INLINE_SYSCALL_CALL (__VA_ARGS__);			     \
-        LIBC_CANCEL_RESET (sc_cancel_oldtype);				     \
-      }									     \
-    sc_ret;								     \
-  })
 
-/* Issue a syscall defined by syscall number plus any other argument
-   required.  Any error will be returned unmodified (including errno).  */
-#define INTERNAL_SYSCALL_CANCEL(...) \
-  ({									     \
-    long int sc_ret;							     \
-    if (SINGLE_THREAD_P) 						     \
-      sc_ret = INTERNAL_SYSCALL_CALL (__VA_ARGS__); 			     \
-    else								     \
-      {									     \
-	int sc_cancel_oldtype = LIBC_CANCEL_ASYNC ();			     \
-	sc_ret = INTERNAL_SYSCALL_CALL (__VA_ARGS__);			     \
-        LIBC_CANCEL_RESET (sc_cancel_oldtype);				     \
-      }									     \
-    sc_ret;								     \
+/* Cancellation macros.  */
+#include <syscall_types.h>
+
+long int __syscall_cancel (__syscall_arg_t nr, __syscall_arg_t arg1,
+			   __syscall_arg_t arg2, __syscall_arg_t arg3,
+			   __syscall_arg_t arg4, __syscall_arg_t arg5,
+			   __syscall_arg_t arg6);
+libc_hidden_proto (__syscall_cancel);
+
+#define __SYSCALL_CANCEL0(name) \
+  __syscall_cancel (__NR_##name, 0, 0, 0, 0, 0, 0)
+#define __SYSCALL_CANCEL1(name, a1) \
+  __syscall_cancel (__NR_##name, __SSC (a1), 0, 0, 0, 0, 0)
+#define __SYSCALL_CANCEL2(name, a1, a2) \
+  __syscall_cancel (__NR_##name, __SSC (a1), __SSC (a2), 0, 0, 0, 0)
+#define __SYSCALL_CANCEL3(name, a1, a2, a3) \
+  __syscall_cancel (__NR_##name, __SSC (a1), __SSC (a2), __SSC (a3), \
+		     0, 0, 0)
+#define __SYSCALL_CANCEL4(name, a1, a2, a3, a4) \
+  __syscall_cancel (__NR_##name, __SSC (a1), __SSC (a2), __SSC (a3), \
+		     __SSC(a4), 0, 0)
+#define __SYSCALL_CANCEL5(name, a1, a2, a3, a4, a5) \
+  __syscall_cancel (__NR_##name, __SSC (a1), __SSC (a2), __SSC (a3), \
+		     __SSC(a4), __SSC (a5), 0)
+#define __SYSCALL_CANCEL6(name, a1, a2, a3, a4, a5, a6) \
+  __syscall_cancel (__NR_##name, __SSC (a1), __SSC (a2), __SSC (a3), \
+		     __SSC (a4), __SSC (a5), __SSC (a6))
+
+#define __SYSCALL_CANCEL_NARGS_X(a,b,c,d,e,f,g,h,n,...) n
+#define __SYSCALL_CANCEL_NARGS(...) \
+  __SYSCALL_CANCEL_NARGS_X (__VA_ARGS__,7,6,5,4,3,2,1,0,)
+#define __SYSCALL_CANCEL_CONCAT_X(a,b)     a##b
+#define __SYSCALL_CANCEL_CONCAT(a,b)       __SYSCALL_CANCEL_CONCAT_X (a, b)
+#define __SYSCALL_CANCEL_DISP(b,...) \
+  __SYSCALL_CANCEL_CONCAT (b,__SYSCALL_CANCEL_NARGS(__VA_ARGS__))(__VA_ARGS__)
+
+#define __SYSCALL_CANCEL_CALL(...) \
+  __SYSCALL_CANCEL_DISP (__SYSCALL_CANCEL, __VA_ARGS__)
+
+/* Issue a cancellable syscall defined by syscall number NAME plus any other
+   argument required.  If an error occurs its value is returned as an negative
+   number unmodified and errno is not set.  */
+#define INTERNAL_SYSCALL_CANCEL(name, args...) \
+  __SYSCALL_CANCEL_CALL (name, args)
+
+/* Issue a cancellable syscall defined first argument plus any other argument
+   required.  If and error occurs its value, the macro returns -1 and sets
+   errno accordingly.  */
+#if IS_IN (rtld)
+/* The loader does not need to handle thread cancellation, use direct
+   syscall instead.  */
+# define SYSCALL_CANCEL(...) INLINE_SYSCALL_CALL (__VA_ARGS__)
+#else
+# define SYSCALL_CANCEL(...) \
+  ({									\
+    long int sc_ret = __SYSCALL_CANCEL_CALL (__VA_ARGS__);		\
+    SYSCALL_CANCEL_RET ((sc_ret));					\
   })
+#endif
+
+#endif /* __ASSEMBLER__  */
 
 /* Machine-dependent sysdep.h files are expected to define the macro
    PSEUDO (function_name, syscall_name) to emit assembly code to define the
@@ -146,3 +208,5 @@ 
 #ifndef INLINE_SYSCALL
 #define INLINE_SYSCALL(name, nr, args...) __syscall_##name (args)
 #endif
+
+#endif /* _SYSDEP_UNIX_H  */
diff --git a/sysdeps/unix/sysv/linux/socketcall.h b/sysdeps/unix/sysv/linux/socketcall.h
index 75c2a6404d..64af566e18 100644
--- a/sysdeps/unix/sysv/linux/socketcall.h
+++ b/sysdeps/unix/sysv/linux/socketcall.h
@@ -87,18 +87,32 @@ 
   })
 
 
-#if IS_IN (libc)
-# define __pthread_enable_asynccancel  __libc_enable_asynccancel
-# define __pthread_disable_asynccancel __libc_disable_asynccancel
-#endif
-
-#define SOCKETCALL_CANCEL(name, args...)				\
-  ({									\
-    int oldtype = LIBC_CANCEL_ASYNC ();					\
-    long int sc_ret = __SOCKETCALL (SOCKOP_##name, args);		\
-    LIBC_CANCEL_RESET (oldtype);					\
-    sc_ret;								\
-  })
-
+#define __SOCKETCALL_CANCEL1(__name, __a1) \
+  SYSCALL_CANCEL (socketcall, __name, \
+     ((long int [1]) { (long int) __a1 }))
+#define __SOCKETCALL_CANCEL2(__name, __a1, __a2) \
+  SYSCALL_CANCEL (socketcall, __name, \
+     ((long int [2]) { (long int) __a1, (long int) __a2 }))
+#define __SOCKETCALL_CANCEL3(__name, __a1, __a2, __a3) \
+  SYSCALL_CANCEL (socketcall, __name, \
+     ((long int [3]) { (long int) __a1, (long int) __a2, (long int) __a3 }))
+#define __SOCKETCALL_CANCEL4(__name, __a1, __a2, __a3, __a4) \
+  SYSCALL_CANCEL (socketcall, __name, \
+     ((long int [4]) { (long int) __a1, (long int) __a2, (long int) __a3, \
+                       (long int) __a4 }))
+#define __SOCKETCALL_CANCEL5(__name, __a1, __a2, __a3, __a4, __a5) \
+  SYSCALL_CANCEL (socketcall, __name, \
+     ((long int [5]) { (long int) __a1, (long int) __a2, (long int) __a3, \
+                       (long int) __a4, (long int) __a5 }))
+#define __SOCKETCALL_CANCEL6(__name, __a1, __a2, __a3, __a4, __a5, __a6) \
+  SYSCALL_CANCEL (socketcall, __name, \
+     ((long int [6]) { (long int) __a1, (long int) __a2, (long int) __a3, \
+                       (long int) __a4, (long int) __a5, (long int) __a6 }))
+
+#define __SOCKETCALL_CANCEL(...) __SOCKETCALL_DISP (__SOCKETCALL_CANCEL,\
+						    __VA_ARGS__)
+
+#define SOCKETCALL_CANCEL(name, args...) \
+   __SOCKETCALL_CANCEL (SOCKOP_##name, args)
 
 #endif /* sys/socketcall.h */
diff --git a/sysdeps/unix/sysv/linux/syscall_cancel.c b/sysdeps/unix/sysv/linux/syscall_cancel.c
new file mode 100644
index 0000000000..003e485b5c
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/syscall_cancel.c
@@ -0,0 +1,62 @@ 
+/* Default cancellation syscall bridge.
+   Copyright (C) 2020 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <sysdep.h>
+#include <pthreadP.h>
+
+#warning "This implementation should be use just as reference or for bootstrapping"
+
+/* This is the generic version of the cancellable syscall code which
+   adds the label guards (__syscall_cancel_arch_{start,end}) used
+   on SIGCANCEL sigcancel_handler (nptl-init.c) to check if the cancelled
+   syscall have side-effects that need to be signaled to program.
+
+   This implementation should be used a reference one to document the
+   implementation constraints: the __syscall_cancel_arch_end should point
+   to the immediate next instruction after the syscall one.  This is because
+   kernel will signal interrupted syscall with side effects by setting
+   the signal frame program counter (on the ucontext_t third argument from
+   SA_SIGINFO signal handler) right after the syscall instruction.
+
+   If the INTERNAL_SYSCALL_NCS macro use more instructions to get the
+   error condition from kernel (as for powerpc and sparc), uses an
+   out of the line helper (as for ARM thumb), or uses a kernel helper
+   gate (as for i686 or ia64) the architecture should adjust the
+   macro or provide a custom __syscall_cancel_arch implementation.   */
+long int
+__syscall_cancel_arch (volatile int *ch, __syscall_arg_t nr,
+		       __syscall_arg_t a1, __syscall_arg_t a2,
+		       __syscall_arg_t a3, __syscall_arg_t a4,
+		       __syscall_arg_t a5, __syscall_arg_t a6)
+{
+#define ADD_LABEL(__label)		\
+  asm volatile (			\
+    ".global " __label "\t\n"		\
+    __label ":\n");
+
+  ADD_LABEL ("__syscall_cancel_arch_start");
+  if (__glibc_unlikely (*ch & CANCELED_BITMASK))
+    __syscall_do_cancel();
+
+  long int result = INTERNAL_SYSCALL_NCS_CALL (nr, a1, a2, a3, a4, a5, a6);
+  ADD_LABEL ("__syscall_cancel_arch_end");
+  if (__glibc_unlikely (INTERNAL_SYSCALL_ERROR_P (result)))
+    return -INTERNAL_SYSCALL_ERRNO (result);
+  return result;
+}
+libc_hidden_def (__syscall_cancel_arch)
diff --git a/sysdeps/unix/sysv/linux/sysdep-cancel.h b/sysdeps/unix/sysv/linux/sysdep-cancel.h
index 61d3348768..20824bc096 100644
--- a/sysdeps/unix/sysv/linux/sysdep-cancel.h
+++ b/sysdeps/unix/sysv/linux/sysdep-cancel.h
@@ -21,47 +21,5 @@ 
 #define _SYSDEP_CANCEL_H
 
 #include <sysdep.h>
-#include <tls.h>
-#include <errno.h>
-
-/* The two functions are in libc.so and not exported.  */
-extern int __libc_enable_asynccancel (void) attribute_hidden;
-extern void __libc_disable_asynccancel (int oldtype) attribute_hidden;
-
-/* The two functions are in librt.so and not exported.  */
-extern int __librt_enable_asynccancel (void) attribute_hidden;
-extern void __librt_disable_asynccancel (int oldtype) attribute_hidden;
-
-/* The two functions are in libpthread.so and not exported.  */
-extern int __pthread_enable_asynccancel (void) attribute_hidden;
-extern void __pthread_disable_asynccancel (int oldtype) attribute_hidden;
-
-/* Set cancellation mode to asynchronous.  */
-#define CANCEL_ASYNC() \
-  __pthread_enable_asynccancel ()
-/* Reset to previous cancellation mode.  */
-#define CANCEL_RESET(oldtype) \
-  __pthread_disable_asynccancel (oldtype)
-
-#if IS_IN (libc)
-/* Same as CANCEL_ASYNC, but for use in libc.so.  */
-# define LIBC_CANCEL_ASYNC() \
-  __libc_enable_asynccancel ()
-/* Same as CANCEL_RESET, but for use in libc.so.  */
-# define LIBC_CANCEL_RESET(oldtype) \
-  __libc_disable_asynccancel (oldtype)
-#elif IS_IN (libpthread)
-# define LIBC_CANCEL_ASYNC() CANCEL_ASYNC ()
-# define LIBC_CANCEL_RESET(val) CANCEL_RESET (val)
-#elif IS_IN (librt)
-# define LIBC_CANCEL_ASYNC() \
-  __librt_enable_asynccancel ()
-# define LIBC_CANCEL_RESET(val) \
-  __librt_disable_asynccancel (val)
-#else
-# define LIBC_CANCEL_ASYNC()	0 /* Just a dummy value.  */
-# define LIBC_CANCEL_RESET(val)	((void)(val)) /* Nothing, but evaluate it.  */
-#endif
-
 
 #endif
diff --git a/sysdeps/unix/sysv/linux/sysdep.h b/sysdeps/unix/sysv/linux/sysdep.h
index 5e7b6c5765..8442de9b13 100644
--- a/sysdeps/unix/sysv/linux/sysdep.h
+++ b/sysdeps/unix/sysv/linux/sysdep.h
@@ -58,6 +58,15 @@ 
     -1l;					\
   })
 
+/* The return error from cancellable syscall has the same semantic as non
+   cancellable ones.  */
+#define SYSCALL_CANCEL_RET(__ret)				\
+  ({								\
+    __glibc_unlikely (INTERNAL_SYSCALL_ERROR_P (__ret))		\
+    ? SYSCALL_ERROR_LABEL (INTERNAL_SYSCALL_ERRNO (__ret))	\
+    : __ret;							\
+   })
+
 /* Provide a dummy argument that can be used to force register
    alignment for register pairs if required by the syscall ABI.  */
 #ifdef __ASSUME_ALIGNED_REGISTER_PAIRS