[v2,7/9] nptl: Implement raise in terms of pthread_kill

Message ID 20210527172823.3461314-8-adhemerval.zanella@linaro.org
State New
Headers show
Series
  • nptl: pthread cancellation refactor
Related show

Commit Message

Khem Raj via Libc-alpha May 27, 2021, 5:28 p.m.
Now that pthread_kill is provided by libc.so it is possible to
implement the generic POSIX implementation as
'pthread_kill(pthread_self(), sig)'.

For Linux implementation, pthread_kill read the targeting TID from
the TCB.  For raise, this it not possible because it would make raise
fail when issue after vfork (where creates the resulting process
has a different TID from the parent, but its TCB is not updated as
for pthread_create).  To make raise use pthread_kill, it is make
usable from vfork by getting the target thread id through gettid
syscall.

Checked on x86_64-linux-gnu and aarch64-linux-gnu.
---
 include/pthread.h               |  5 ++++
 nptl/pthreadP.h                 |  4 ++-
 nptl/pthread_kill.c             | 40 ++++++++++++++++---------
 nptl/pthread_self.c             |  4 ++-
 sysdeps/htl/pthreadP.h          |  2 --
 sysdeps/posix/raise.c           | 11 +++++--
 sysdeps/unix/sysv/linux/raise.c | 52 ---------------------------------
 7 files changed, 47 insertions(+), 71 deletions(-)
 delete mode 100644 sysdeps/unix/sysv/linux/raise.c

-- 
2.30.2

Comments

Khem Raj via Libc-alpha June 1, 2021, 12:40 p.m. | #1
* Adhemerval Zanella via Libc-alpha:

> For Linux implementation, pthread_kill read the targeting TID from

> the TCB.  For raise, this it not possible because it would make raise

> fail when issue after vfork (where creates the resulting process

> has a different TID from the parent, but its TCB is not updated as

> for pthread_create).  To make raise use pthread_kill, it is make

> usable from vfork by getting the target thread id through gettid

> syscall.


Please add the vfork information as a comment in pthread_kill.
Otherwise looks good.

Thanks,
Florian
Khem Raj via Libc-alpha June 2, 2021, 1:14 p.m. | #2
On 01/06/2021 09:40, Florian Weimer wrote:
> * Adhemerval Zanella via Libc-alpha:

> 

>> For Linux implementation, pthread_kill read the targeting TID from

>> the TCB.  For raise, this it not possible because it would make raise

>> fail when issue after vfork (where creates the resulting process

>> has a different TID from the parent, but its TCB is not updated as

>> for pthread_create).  To make raise use pthread_kill, it is make

>> usable from vfork by getting the target thread id through gettid

>> syscall.

> 

> Please add the vfork information as a comment in pthread_kill.

> Otherwise looks good.


I added the following comment:

  if (pd == THREAD_SELF)
    /* It is a special case to handle raise() implementation after a vfork
       call (which does not update the PD tid field).  */
    tid = INLINE_SYSCALL_CALL (gettid);

Patch

diff --git a/include/pthread.h b/include/pthread.h
index a3e1cf51b0..1158919247 100644
--- a/include/pthread.h
+++ b/include/pthread.h
@@ -16,4 +16,9 @@  extern int __pthread_barrier_wait (pthread_barrier_t *__barrier)
 
 /* This function is called to initialize the pthread library.  */
 extern void __pthread_initialize (void) __attribute__ ((weak));
+
+extern int __pthread_kill (pthread_t threadid, int signo);
+
+extern pthread_t __pthread_self (void);
+
 #endif
diff --git a/nptl/pthreadP.h b/nptl/pthreadP.h
index 3e7a4f52ab..618922f47a 100644
--- a/nptl/pthreadP.h
+++ b/nptl/pthreadP.h
@@ -508,11 +508,13 @@  extern int __pthread_once (pthread_once_t *once_control,
 libc_hidden_proto (__pthread_once)
 extern int __pthread_atfork (void (*prepare) (void), void (*parent) (void),
 			     void (*child) (void));
-extern pthread_t __pthread_self (void);
+libc_hidden_proto (__pthread_self)
 extern int __pthread_equal (pthread_t thread1, pthread_t thread2);
 extern int __pthread_detach (pthread_t th);
 libc_hidden_proto (__pthread_detach)
 extern int __pthread_kill (pthread_t threadid, int signo);
+libc_hidden_proto (__pthread_kill)
+extern int __pthread_cancel (pthread_t th);
 extern void __pthread_exit (void *value) __attribute__ ((__noreturn__));
 libc_hidden_proto (__pthread_exit)
 extern int __pthread_join (pthread_t threadid, void **thread_return);
diff --git a/nptl/pthread_kill.c b/nptl/pthread_kill.c
index ad7e011779..0392c3f9e5 100644
--- a/nptl/pthread_kill.c
+++ b/nptl/pthread_kill.c
@@ -28,24 +28,38 @@  __pthread_kill (pthread_t threadid, int signo)
   if (__is_internal_signal (signo))
     return EINVAL;
 
-  /* 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.  */
+  pid_t tid;
   struct pthread *pd = (struct pthread *) threadid;
-  pid_t tid = atomic_forced_read (pd->tid);
-  if (__glibc_unlikely (tid <= 0))
-    /* Not a valid thread handle.  */
-    return ESRCH;
 
-  /* We have a special syscall to do the work.  */
-  pid_t pid = __getpid ();
+  if (pd == THREAD_SELF)
+    tid = INLINE_SYSCALL_CALL (gettid);
+  else
+    /* 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.  */
+    tid = atomic_forced_read (pd->tid);
 
-  int val = INTERNAL_SYSCALL_CALL (tgkill, pid, tid, signo);
-  return (INTERNAL_SYSCALL_ERROR_P (val)
-	  ? INTERNAL_SYSCALL_ERRNO (val) : 0);
+  int val;
+  if (__glibc_likely (tid > 0))
+    {
+      pid_t pid = __getpid ();
+
+      val = INTERNAL_SYSCALL_CALL (tgkill, pid, tid, signo);
+      val = (INTERNAL_SYSCALL_ERROR_P (val)
+	    ? INTERNAL_SYSCALL_ERRNO (val) : 0);
+    }
+  else
+    val = ESRCH;
+
+  return val;
 }
+/* Some architectures (for instance arm) might pull raise through libgcc, so
+   avoid the symbol version if it ends up being used on ld.so.  */
+#if !IS_IN(rtld)
+libc_hidden_def (__pthread_kill)
 versioned_symbol (libc, __pthread_kill, pthread_kill, GLIBC_2_34);
 
-#if OTHER_SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_34)
+# if OTHER_SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_34)
 compat_symbol (libc, __pthread_kill, pthread_kill, GLIBC_2_0);
+# endif
 #endif
diff --git a/nptl/pthread_self.c b/nptl/pthread_self.c
index f877a2e6bd..196d93fb8e 100644
--- a/nptl/pthread_self.c
+++ b/nptl/pthread_self.c
@@ -20,7 +20,9 @@ 
 #include <tls.h>
 
 pthread_t
-pthread_self (void)
+__pthread_self (void)
 {
   return (pthread_t) THREAD_SELF;
 }
+libc_hidden_def (__pthread_self)
+weak_alias (__pthread_self, pthread_self)
diff --git a/sysdeps/htl/pthreadP.h b/sysdeps/htl/pthreadP.h
index 8e2cf2ce65..3b357b7bdc 100644
--- a/sysdeps/htl/pthreadP.h
+++ b/sysdeps/htl/pthreadP.h
@@ -31,8 +31,6 @@  extern void __pthread_init_static_tls (struct link_map *) attribute_hidden;
 
 /* These represent the interface used by glibc itself.  */
 
-extern pthread_t __pthread_self (void);
-extern int __pthread_kill (pthread_t threadid, int signo);
 extern struct __pthread **__pthread_threads;
 
 extern int __pthread_mutex_init (pthread_mutex_t *__mutex, const pthread_mutexattr_t *__attr);
diff --git a/sysdeps/posix/raise.c b/sysdeps/posix/raise.c
index 9fdb4d538b..4806c0cc63 100644
--- a/sysdeps/posix/raise.c
+++ b/sysdeps/posix/raise.c
@@ -16,13 +16,20 @@ 
    <https://www.gnu.org/licenses/>.  */
 
 #include <signal.h>
-#include <unistd.h>
+#include <errno.h>
+#include <pthread.h>
 
 /* Raise the signal SIG.  */
 int
 raise (int sig)
 {
-  return __kill (__getpid (), sig);
+  int ret = __pthread_kill (__pthread_self (), sig);
+  if (ret != 0)
+    {
+      __set_errno (ret);
+      ret = -1;
+    }
+  return ret;
 }
 libc_hidden_def (raise)
 weak_alias (raise, gsignal)
diff --git a/sysdeps/unix/sysv/linux/raise.c b/sysdeps/unix/sysv/linux/raise.c
deleted file mode 100644
index 9be3b37f53..0000000000
--- a/sysdeps/unix/sysv/linux/raise.c
+++ /dev/null
@@ -1,52 +0,0 @@ 
-/* Copyright (C) 2002-2021 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 <signal.h>
-#include <sysdep.h>
-#include <errno.h>
-#include <sys/types.h>
-#include <unistd.h>
-#include <internal-signals.h>
-
-int
-raise (int sig)
-{
-  /* rt_sigprocmask may fail if:
-
-     1. sigsetsize != sizeof (sigset_t) (EINVAL)
-     2. a failure in copy from/to user space (EFAULT)
-     3. an invalid 'how' operation (EINVAL)
-
-     The first case is already handle in glibc syscall call by using the arch
-     defined _NSIG.  Second case is handled by using a stack allocated mask.
-     The last one should be handled by the block/unblock functions.  */
-
-  sigset_t set;
-  __libc_signal_block_app (&set);
-
-  pid_t pid = INTERNAL_SYSCALL_CALL (getpid);
-  pid_t tid = INTERNAL_SYSCALL_CALL (gettid);
-
-  int ret = INLINE_SYSCALL_CALL (tgkill, pid, tid, sig);
-
-  __libc_signal_restore_set (&set);
-
-  return ret;
-}
-libc_hidden_def (raise)
-weak_alias (raise, gsignal)