New: async-signal-safe functions list in Linux
https://bugzilla.kernel.org/show_bug.cgi?id=25292
Summary: async-signal-safe functions list in Linux
Product: Documentation
Version: unspecified
Platform: All
OS/Version: Linux
Tree: Mainline
Status: NEW
Severity: normal
Priority: P1
Component: man-pages
AssignedTo: documentation_man-pages-ztI5WcYan/[email protected]
ReportedBy: [email protected]
Regression: No
Signal(7) described which functions are async-signal-safe. But it is only written POSIX definition, is not described linux implementation specific limit. And it should be.
I have three example.
1. fork
glibc malloc are calling pthread_atfork() internally, therefore our fork is async signal unsafe since long time ago.
http://sourceware.org/bugzilla/show_bug.cgi?id=4737
The standard comitte has decided to remove fork() from async-signal-safe functions in future standard. (see following defect reports)
http://www.opengroup.org/austin/aardvark/latest/xshbug3.txt
Quoted 23 lines
_____________________________________________________________________________
COMMENT Enhancement Request Number 15
rajani.g.k:xxxxxx Defect in XSH 2.4.3 (rdvk# 6)
{GKRFORK012009} Thu, 8 Jan 2009 07:41:10 GMT
_____________________________________________________________________________
Accept_____Accept as markedbelow_X___Duplicate_____Reject_____
Rationale for rejected or partial changes:We agreed not to send this down the interps track yet.
The standard is clear and concerns are being forwarded to the sponsor. A previous interpretation 1003.1c-1995 #37, and also ERN XSHbug2145 have addressed the same issue, but still the problem has remained unresolved.
Because of the problems which exist here it has become
clear that an application usingpthread_atfork(), even if the application itself did not callpthread_atfork(), may have hadpthread_atfork()handlers installed by a third party library or the implementation. Therefore callingfork()from an asynchronous signal handler is undefined. Therefore we are removingfork()from the list of
async-signal-safe functions.
Quoted 5 lines
Recommendations for a future revision:
A future revision should mandateposix_spawn()and add that to the list of async-signal-safe functions.
Removefork()from the list of async-signal-safe functions.
[ 12 Feb 2009 - we had no consensus on the changes for a future revision]
2. aio_suspend
It is using pthread_mutex_lock() internally.
glibc/sysdeps/pthread/aio_suspend.c
------------------------------------------
intaio_suspend (list, nent, timeout)
const struct aiocb *const list[];
int nent;
const struct timespec *timeout;{
(snip)
/* Request the mutex. */ pthread_mutex_lock (&__aio_requests_mutex);
3. execle
It is using realloc internally.
glibc/posix/execle.c
----------------------------------------------------------
int
execle (const char *path, const char *arg, ...)
{
#define INITIAL_ARGV_MAX 1024
size_t argv_max = INITIAL_ARGV_MAX;
const char *initial_argv[INITIAL_ARGV_MAX];
const char **argv = initial_argv;
va_list args;
argv[0] = arg;
va_start (args, arg);
unsigned int i = 0;
while (argv[i++] != NULL)
{
if (i == argv_max)
{
argv_max *= 2;
const char **nptr = realloc (argv == initial_argv ? NULL : argv,
argv_max * sizeof (const char *));
if (nptr == NULL)
{Can you please consider to update signal(7) man page?
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[Bug 25292] async-signal-safe functions list in Linux
https://bugzilla.kernel.org/show_bug.cgi?id=25292
[email protected] changed:
What |Removed |Added
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CC| |[email protected]
--- Comment #1 from [email protected] --- This bug is outdated , please tell against a newer kernel. Thanks Nick
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[Bug 25292] async-signal-safe functions list in Linux
In reply to a message not in the archivehttps://bugzilla.kernel.org/show_bug.cgi?id=25292
--- Comment #2 from KOSAKI Motohiro <[email protected]> --- ?
My example don't depend on kernel version. All of them describes glibc implementations.
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[Bug 25292] async-signal-safe functions list in Linux
In reply to a message not in the archivehttps://bugzilla.kernel.org/show_bug.cgi?id=25292
Alan <alan-qBU/[email protected]> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |alan-qBU/[email protected]
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