[03/13] posix: Consolidate Linux nanosleep syscall

Message ID 1494611894-9282-3-git-send-email-adhemerval.zanella@linaro.org
State New
Headers show
Series
  • [01/13] posix: Consolidate Linux pause syscall
Related show

Commit Message

Adhemerval Zanella May 12, 2017, 5:58 p.m.
This patch consolidates the nanosleep Linux syscall generation on
sysdeps/unix/sysv/linux/nanosleep.c.  It basically removes it from
architectures auto-generation list.

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.

	* nptl/Makefile (CFLAGS-nanosleep.c): New rule.
	* posix/Makefile (CFLAGS-nanosleep.c): Likewise.
	* sysdeps/unix/sysv/linux/nanosleep.c: New file.
	* sysdeps/unix/sysv/linux/syscalls.list: Remove nanosleep from
	auto-generated list.
---
 ChangeLog                             |  6 ++++++
 nptl/Makefile                         |  1 +
 posix/Makefile                        |  1 +
 sysdeps/unix/sysv/linux/nanosleep.c   | 30 ++++++++++++++++++++++++++++++
 sysdeps/unix/sysv/linux/syscalls.list |  1 -
 5 files changed, 38 insertions(+), 1 deletion(-)
 create mode 100644 sysdeps/unix/sysv/linux/nanosleep.c

-- 
2.7.4

Comments

Florian Weimer May 12, 2017, 6:21 p.m. | #1
On 05/12/2017 07:58 PM, Adhemerval Zanella wrote:
> +++ b/nptl/Makefile


> +CFLAGS-nanosleep.c = -fexceptions -fasynchronous-unwind-tables



> +++ b/posix/Makefile


> +CFLAGS-nanosleep.c = -fexceptions


Why the discrepancy?  I suppose both implementations could be called in 
a multi-threaded program.

Thanks,
Florian
Adhemerval Zanella May 12, 2017, 6:30 p.m. | #2
On 12/05/2017 15:21, Florian Weimer wrote:
> On 05/12/2017 07:58 PM, Adhemerval Zanella wrote:

>> +++ b/nptl/Makefile

> 

>> +CFLAGS-nanosleep.c = -fexceptions -fasynchronous-unwind-tables

> 

> 

>> +++ b/posix/Makefile

> 

>> +CFLAGS-nanosleep.c = -fexceptions

> 

> Why the discrepancy?  I suppose both implementations could be called in a multi-threaded program.


I do not recall a reason why these are different, I will set both to
-fexceptions -fasynchronous-unwind-tables.  AFAIK -fexception is the
required flag for cancelable syscall to work correctly, while 
-fasynchronous-unwind-tables is make it work also through signals
(not really sure though).  So I would say to be safe we should set
both.
Joseph Myers May 15, 2017, 11:36 a.m. | #3
On Mon, 15 May 2017, Florian Weimer wrote:

> Technically, __gcc_personality_v0 is part of the ABI, so there could still be

> user code out there that uses it.  And of course, Ada and C++ code which is

> called from glibc code (or which runs from a signal handler that interrupts

> glibc code) could have stack frames with crucial unwinding information when

> thread cancellation happens.

> 

> In order to reach those stack frames, the cancellation code needs to unwind

> through glibc code.  This could be any code in glibc which calls a function

> which is a cancellation point.

> 

> Based on that, I think we should compile all of glibc with unwinding support,

> and considering that asynchronous cancellation can happen through synchronous

> cancellation within signal handlers, we need both -fexceptions *and*

> -fasynchronous-unwind-tables.


See <https://sourceware.org/ml/libc-alpha/2015-10/msg00569.html> and 
followups for discussion of the circumstances when those options may be 
needed.

-- 
Joseph S. Myers
joseph@codesourcery.com
Florian Weimer May 15, 2017, 11:46 a.m. | #4
On 05/15/2017 01:36 PM, Joseph Myers wrote:

> See <https://sourceware.org/ml/libc-alpha/2015-10/msg00569.html> and

> followups for discussion of the circumstances when those options may be

> needed.


Interesting.  So the C frontend can actually generate code which invokes 
the personality routine (via the cleanup attribute).

I wonder if we can use this to make cancellation safer, at least within 
glibc.

Florian

Patch

diff --git a/nptl/Makefile b/nptl/Makefile
index d39bb50..cdf69bd 100644
--- a/nptl/Makefile
+++ b/nptl/Makefile
@@ -216,6 +216,7 @@  CFLAGS-sendmsg.c = -fexceptions -fasynchronous-unwind-tables
 CFLAGS-close.c = -fexceptions -fasynchronous-unwind-tables
 CFLAGS-read.c = -fexceptions -fasynchronous-unwind-tables
 CFLAGS-write.c = -fexceptions -fasynchronous-unwind-tables
+CFLAGS-nanosleep.c = -fexceptions -fasynchronous-unwind-tables
 
 CFLAGS-pt-system.c = -fexceptions
 
diff --git a/posix/Makefile b/posix/Makefile
index 0025d8a..9f186cd 100644
--- a/posix/Makefile
+++ b/posix/Makefile
@@ -232,6 +232,7 @@  CFLAGS-execle.os = -fomit-frame-pointer
 CFLAGS-execl.os = -fomit-frame-pointer
 CFLAGS-execvp.os = -fomit-frame-pointer
 CFLAGS-execlp.os = -fomit-frame-pointer
+CFLAGS-nanosleep.c = -fexceptions
 
 tstgetopt-ARGS = -a -b -cfoobar --required foobar --optional=bazbug \
 		--none random --col --color --colour
diff --git a/sysdeps/unix/sysv/linux/nanosleep.c b/sysdeps/unix/sysv/linux/nanosleep.c
new file mode 100644
index 0000000..b352f84
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/nanosleep.c
@@ -0,0 +1,30 @@ 
+/* Linux high resolution nanosleep implementation.
+   Copyright (C) 2017 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 <time.h>
+#include <sysdep-cancel.h>
+
+/* Pause execution for a number of nanoseconds.  */
+int
+__nanosleep (const struct timespec *requested_time,
+	     struct timespec *remaining)
+{
+  return SYSCALL_CANCEL (nanosleep, requested_time, remaining);
+}
+libc_hidden_def (__nanosleep)
+weak_alias (__nanosleep, nanosleep)
diff --git a/sysdeps/unix/sysv/linux/syscalls.list b/sysdeps/unix/sysv/linux/syscalls.list
index eab30dd..7fca6f8 100644
--- a/sysdeps/unix/sysv/linux/syscalls.list
+++ b/sysdeps/unix/sysv/linux/syscalls.list
@@ -42,7 +42,6 @@  mount		EXTRA	mount		i:sssip	__mount	mount
 mremap		EXTRA	mremap		b:ainip	__mremap	mremap
 munlock		-	munlock		i:ai	munlock
 munlockall	-	munlockall	i:	munlockall
-nanosleep	-	nanosleep	Ci:pp	__nanosleep	nanosleep
 nfsservctl	EXTRA	nfsservctl	i:ipp	nfsservctl
 pipe		-	pipe		i:f	__pipe		pipe
 pipe2		-	pipe2		i:fi	__pipe2		pipe2