[09/18] linux: Remove time64-support

Message ID 20210617115104.1359598-10-adhemerval.zanella@linaro.org
State New
Headers show
Series
  • More y2038 fixes
Related show

Commit Message

Michael Hudson-Doyle via Libc-alpha June 17, 2021, 11:50 a.m.
It breaks the usage case of live migration like CRIU or similar
and most usages can be optimized away by either building glibc with
a minimum 5.1 kernel or by using the 32-bit syscall for the common
case.

Checked on i686-linux-gnu on a 4.15 kernel and on a 5.11 kernel
(with and without --enable-kernel=5.1) and on x86_64-linux-gnu.
---
 sysdeps/unix/sysv/linux/Makefile         |  2 +-
 sysdeps/unix/sysv/linux/time64-support.c | 23 --------
 sysdeps/unix/sysv/linux/time64-support.h | 70 ------------------------
 3 files changed, 1 insertion(+), 94 deletions(-)
 delete mode 100644 sysdeps/unix/sysv/linux/time64-support.c
 delete mode 100644 sysdeps/unix/sysv/linux/time64-support.h

-- 
2.30.2

Comments

Lukasz Majewski June 21, 2021, 7:43 a.m. | #1
On Thu, 17 Jun 2021 08:50:55 -0300
Adhemerval Zanella <adhemerval.zanella@linaro.org> wrote:

> It breaks the usage case of live migration like CRIU or similar

> and most usages can be optimized away by either building glibc with

> a minimum 5.1 kernel or by using the 32-bit syscall for the common

> case.

> 

> Checked on i686-linux-gnu on a 4.15 kernel and on a 5.11 kernel

> (with and without --enable-kernel=5.1) and on x86_64-linux-gnu.

> ---

>  sysdeps/unix/sysv/linux/Makefile         |  2 +-

>  sysdeps/unix/sysv/linux/time64-support.c | 23 --------

>  sysdeps/unix/sysv/linux/time64-support.h | 70

> ------------------------ 3 files changed, 1 insertion(+), 94

> deletions(-) delete mode 100644

> sysdeps/unix/sysv/linux/time64-support.c delete mode 100644

> sysdeps/unix/sysv/linux/time64-support.h

> 

> diff --git a/sysdeps/unix/sysv/linux/Makefile

> b/sysdeps/unix/sysv/linux/Makefile index 710169a454..982755f980 100644

> --- a/sysdeps/unix/sysv/linux/Makefile

> +++ b/sysdeps/unix/sysv/linux/Makefile

> @@ -61,7 +61,7 @@ sysdep_routines += adjtimex clone umount umount2

> readahead sysctl \ open_by_handle_at mlock2 pkey_mprotect pkey_set

> pkey_get \ timerfd_gettime timerfd_settime prctl \

>  		   process_vm_readv process_vm_writev clock_adjtime \

> -		   time64-support pselect32 select32 \

> +		   pselect32 select32 \

>  		   xstat fxstat lxstat xstat64 fxstat64 lxstat64 \

>  		   fxstatat fxstatat64 \

>  		   xmknod xmknodat convert_scm_timestamps

> diff --git a/sysdeps/unix/sysv/linux/time64-support.c

> b/sysdeps/unix/sysv/linux/time64-support.c deleted file mode 100644

> index 0718e7421b..0000000000

> --- a/sysdeps/unix/sysv/linux/time64-support.c

> +++ /dev/null

> @@ -1,23 +0,0 @@

> -/* Auxiliary definitions for 64-bit time_t support.

> -   Copyright (C) 2020-2021 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/>.  */

> -

> -#include <time64-support.h>

> -

> -#ifndef __ASSUME_TIME64_SYSCALLS

> -int __time64_support = 1;

> -#endif

> diff --git a/sysdeps/unix/sysv/linux/time64-support.h

> b/sysdeps/unix/sysv/linux/time64-support.h deleted file mode 100644

> index 8466d37f8f..0000000000

> --- a/sysdeps/unix/sysv/linux/time64-support.h

> +++ /dev/null

> @@ -1,70 +0,0 @@

> -/* Auxiliary definitions for 64-bit time_t support.

> -   Copyright (C) 2020-2021 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/>.  */

> -

> -#include <stdbool.h>

> -#include <atomic.h>

> -

> -/* These helper functions are used to optimize the 64-bit time_t

> support on

> -   configurations that requires support for 32-bit time_t fallback

> -   (!__ASSUME_TIME64_SYSCALLS).  The idea is once the kernel

> advertises that

> -   it does not have 64-bit time_t support, glibc will stop to try

> issue the

> -   64-bit time_t syscall altogether.

> -

> -   For instance:

> -

> -     #ifndef __NR_symbol_time64

> -     # define __NR_symbol_time64 __NR_symbol

> -     #endif

> -     int r;

> -     if (supports_time64 ())

> -       {

> -         r = INLINE_SYSCALL_CALL (symbol, ...);

> -         if (r == 0 || errno != ENOSYS)

> -	   return r;

> -

> -         mark_time64_unsupported ();

> -       }

> -     #ifndef __ASSUME_TIME64_SYSCALLS

> -     <32-bit fallback syscall>

> -     #endif

> -     return r;

> -

> -   On configuration with default 64-bit time_t this optimization

> should be

> -   optimized away by the compiler resulting in no overhead.  */

> -

> -#ifndef __ASSUME_TIME64_SYSCALLS

> -extern int __time64_support attribute_hidden;

> -#endif

> -

> -static inline bool

> -supports_time64 (void)

> -{

> -#ifdef __ASSUME_TIME64_SYSCALLS

> -  return true;

> -#else

> -  return atomic_load_relaxed (&__time64_support) != 0;

> -#endif

> -}

> -

> -static inline void

> -mark_time64_unsupported (void)

> -{

> -#ifndef __ASSUME_TIME64_SYSCALLS

> -  atomic_store_relaxed (&__time64_support, 0);

> -#endif

> -}


Reviewed-by: Lukasz Majewski <lukma@denx.de>



Best regards,

Lukasz Majewski

--

DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma@denx.de

Patch

diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
index 710169a454..982755f980 100644
--- a/sysdeps/unix/sysv/linux/Makefile
+++ b/sysdeps/unix/sysv/linux/Makefile
@@ -61,7 +61,7 @@  sysdep_routines += adjtimex clone umount umount2 readahead sysctl \
 		   open_by_handle_at mlock2 pkey_mprotect pkey_set pkey_get \
 		   timerfd_gettime timerfd_settime prctl \
 		   process_vm_readv process_vm_writev clock_adjtime \
-		   time64-support pselect32 select32 \
+		   pselect32 select32 \
 		   xstat fxstat lxstat xstat64 fxstat64 lxstat64 \
 		   fxstatat fxstatat64 \
 		   xmknod xmknodat convert_scm_timestamps
diff --git a/sysdeps/unix/sysv/linux/time64-support.c b/sysdeps/unix/sysv/linux/time64-support.c
deleted file mode 100644
index 0718e7421b..0000000000
--- a/sysdeps/unix/sysv/linux/time64-support.c
+++ /dev/null
@@ -1,23 +0,0 @@ 
-/* Auxiliary definitions for 64-bit time_t support.
-   Copyright (C) 2020-2021 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/>.  */
-
-#include <time64-support.h>
-
-#ifndef __ASSUME_TIME64_SYSCALLS
-int __time64_support = 1;
-#endif
diff --git a/sysdeps/unix/sysv/linux/time64-support.h b/sysdeps/unix/sysv/linux/time64-support.h
deleted file mode 100644
index 8466d37f8f..0000000000
--- a/sysdeps/unix/sysv/linux/time64-support.h
+++ /dev/null
@@ -1,70 +0,0 @@ 
-/* Auxiliary definitions for 64-bit time_t support.
-   Copyright (C) 2020-2021 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/>.  */
-
-#include <stdbool.h>
-#include <atomic.h>
-
-/* These helper functions are used to optimize the 64-bit time_t support on
-   configurations that requires support for 32-bit time_t fallback
-   (!__ASSUME_TIME64_SYSCALLS).  The idea is once the kernel advertises that
-   it does not have 64-bit time_t support, glibc will stop to try issue the
-   64-bit time_t syscall altogether.
-
-   For instance:
-
-     #ifndef __NR_symbol_time64
-     # define __NR_symbol_time64 __NR_symbol
-     #endif
-     int r;
-     if (supports_time64 ())
-       {
-         r = INLINE_SYSCALL_CALL (symbol, ...);
-         if (r == 0 || errno != ENOSYS)
-	   return r;
-
-         mark_time64_unsupported ();
-       }
-     #ifndef __ASSUME_TIME64_SYSCALLS
-     <32-bit fallback syscall>
-     #endif
-     return r;
-
-   On configuration with default 64-bit time_t this optimization should be
-   optimized away by the compiler resulting in no overhead.  */
-
-#ifndef __ASSUME_TIME64_SYSCALLS
-extern int __time64_support attribute_hidden;
-#endif
-
-static inline bool
-supports_time64 (void)
-{
-#ifdef __ASSUME_TIME64_SYSCALLS
-  return true;
-#else
-  return atomic_load_relaxed (&__time64_support) != 0;
-#endif
-}
-
-static inline void
-mark_time64_unsupported (void)
-{
-#ifndef __ASSUME_TIME64_SYSCALLS
-  atomic_store_relaxed (&__time64_support, 0);
-#endif
-}