[01/13] posix: Consolidate Linux pause syscall
Commit Message
This patch consolidates the pause Linux implementation on
sysdeps/unix/sysv/linux/pause.c. If defined the pause syscall
(__NR_pause) will be used, other ppoll with 0 arguments will be
used instead.
It has the small advantage of generic pause implementation with
uses rt_sigprocmask plus rt_sigsuspend because it requires only
one syscall and the pause is done atomically regarding signal
handling (for instance, pause may not be interrupted if the
signal arrives between the rt_sigprocmask and rt_sigsuspend
syscall).
Checked on i686-linux-gnu, x86_64-linux-gnu, x86_64-linux-gnux32,
arch64-linux-gnu, arm-linux-gnueabihf, powerpc64le-linux-gnu,
sparc64-linux-gnu, and sparcv9-linux-gnu.
* sysdeps/unix/sysv/linux/generic/pause.c: Remove file.
* sysdeps/unix/sysv/linux/sparc/sparc64/pause.c: Likewise.
* sysdeps/unix/sysv/linux/sparc/kernel-features.h [__arch64__]
(__NR_pause): Undefine.
* sysdeps/unix/sysv/linux/pause.c: New file.
* sysdeps/unix/sysv/linux/syscalls.list: Remove pause from
auto-generation list.
---
ChangeLog | 10 ++++++++++
sysdeps/unix/sysv/linux/{generic => }/pause.c | 18 +++++++-----------
sysdeps/unix/sysv/linux/sparc/kernel-features.h | 6 ++++++
sysdeps/unix/sysv/linux/sparc/sparc64/pause.c | 9 ---------
sysdeps/unix/sysv/linux/syscalls.list | 1 -
5 files changed, 23 insertions(+), 21 deletions(-)
rename sysdeps/unix/sysv/linux/{generic => }/pause.c (75%)
delete mode 100644 sysdeps/unix/sysv/linux/sparc/sparc64/pause.c
Comments
On 05/12/2017 07:58 PM, Adhemerval Zanella wrote:
> +/* sparc64 defines __NR_pause, however it is not supported (ENOSYS).
> + Undefine so pause.c can use a correct alternative. */
> +# ifdef __NR_pause
> +# undef __NR_pause
> +# endif
I think you can #undef unconditionally, there isn't a warning for that.
+ return SYSCALL_CANCEL (ppoll, 0, 0, 0, 0, 0);
I think some of the arguments should be NULL instead of 0.
I'm not completely sure if an empty ppoll without a timeout has the
required semantics, but I can't think of a reason why it would not work.
Thanks,
Florian
On 12/05/2017 15:15, Florian Weimer wrote:
> On 05/12/2017 07:58 PM, Adhemerval Zanella wrote:
>> +/* sparc64 defines __NR_pause, however it is not supported (ENOSYS).
>> + Undefine so pause.c can use a correct alternative. */
>> +# ifdef __NR_pause
>> +# undef __NR_pause
>> +# endif
>
> I think you can #undef unconditionally, there isn't a warning for that.
Alright, I will change it.
>
> + return SYSCALL_CANCEL (ppoll, 0, 0, 0, 0, 0);
>
> I think some of the arguments should be NULL instead of 0.
I will change to SYSCALL_CANCEL (ppoll, NULL, 0, NULL, NULL).
>
> I'm not completely sure if an empty ppoll without a timeout has the required semantics, but I can't think of a reason why it would not work.
I though about Linux syscall with similar semantics regarding signals,
but I couldn't find one.
similarity index 75%
rename from sysdeps/unix/sysv/linux/generic/pause.c
rename to sysdeps/unix/sysv/linux/pause.c
@@ -1,6 +1,6 @@
-/* Copyright (C) 2011-2017 Free Software Foundation, Inc.
+/* Linux pause syscall implementation.
+ Copyright (C) 2017 Free Software Foundation, Inc.
This file is part of the GNU C Library.
- Contributed by Chris Metcalf <cmetcalf@tilera.com>, 2011.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
@@ -26,14 +26,10 @@
int
__libc_pause (void)
{
- sigset_t set;
-
- int rc =
- SYSCALL_CANCEL (rt_sigprocmask, SIG_BLOCK, NULL, &set, _NSIG / 8);
- if (rc == 0)
- rc = SYSCALL_CANCEL (rt_sigsuspend, &set, _NSIG / 8);
-
- return rc;
+#ifdef __NR_pause
+ return SYSCALL_CANCEL (pause);
+#else
+ return SYSCALL_CANCEL (ppoll, 0, 0, 0, 0, 0);
+#endif
}
-
weak_alias (__libc_pause, pause)
@@ -32,6 +32,12 @@
# undef __ASSUME_ACCEPT_SYSCALL
# undef __ASSUME_CONNECT_SYSCALL
# undef __ASSUME_RECVFROM_SYSCALL
+#else
+/* sparc64 defines __NR_pause, however it is not supported (ENOSYS).
+ Undefine so pause.c can use a correct alternative. */
+# ifdef __NR_pause
+# undef __NR_pause
+# endif
#endif
/* sparc only supports ipc syscall. */
deleted file mode 100644
@@ -1,9 +0,0 @@
-#include <errno.h>
-#include <signal.h>
-#include <unistd.h>
-#include <sysdep-cancel.h>
-
-#define __sigprocmask(how, set, oset) \
- INLINE_SYSCALL (rt_sigprocmask, 4, how, set, oset, _NSIG / 8)
-
-#include <sysdeps/posix/pause.c>
@@ -44,7 +44,6 @@ munlock - munlock i:ai munlock
munlockall - munlockall i: munlockall
nanosleep - nanosleep Ci:pp __nanosleep nanosleep
nfsservctl EXTRA nfsservctl i:ipp nfsservctl
-pause - pause Ci: __libc_pause pause
pipe - pipe i:f __pipe pipe
pipe2 - pipe2 i:fi __pipe2 pipe2
pivot_root EXTRA pivot_root i:ss pivot_root