musl/src/signal/sigtimedwait.c

#include <signal.h>
#include <errno.h>
#include "syscall.h"
#include "libc.h"

int sigtimedwait(const sigset_t *mask, siginfo_t *si, const struct timespec *timeout)
{
	int ret;
	CANCELPT_BEGIN;
	do {
		ret = syscall(__NR_rt_sigtimedwait, mask, si, timeout, 8);
		if (ret<0) CANCELPT_TRY;
	} while (ret<0 && errno==EINTR);
	CANCELPT_END;
	return ret;
}
initial check-in, version 0.5.0 2011-02-12 00:22:29 -05:00			`#include <signal.h>`
don't fail with EINTR in sigtimedwait POSIX allows either behavior, but sigwait is not allowed to fail with EINTR, so the retry loop would have to be in one or the other anyway. 2011-03-10 10:43:09 -05:00			`#include <errno.h>`
initial check-in, version 0.5.0 2011-02-12 00:22:29 -05:00			`#include "syscall.h"`
make sigtimedwait a cancellation point 2011-03-10 10:59:50 -05:00			`#include "libc.h"`
initial check-in, version 0.5.0 2011-02-12 00:22:29 -05:00
			`int sigtimedwait(const sigset_t mask, siginfo_t si, const struct timespec *timeout)`
			`{`
don't fail with EINTR in sigtimedwait POSIX allows either behavior, but sigwait is not allowed to fail with EINTR, so the retry loop would have to be in one or the other anyway. 2011-03-10 10:43:09 -05:00			`int ret;`
make sigtimedwait a cancellation point 2011-03-10 10:59:50 -05:00			`CANCELPT_BEGIN;`
don't fail with EINTR in sigtimedwait POSIX allows either behavior, but sigwait is not allowed to fail with EINTR, so the retry loop would have to be in one or the other anyway. 2011-03-10 10:43:09 -05:00			`do {`
syscall overhaul part two - unify public and internal syscall interface with this patch, the syscallN() functions are no longer needed; a variadic syscall() macro allows syscalls with anywhere from 0 to 6 arguments to be made with a single macro name. also, manually casting each non-integer argument with (long) is no longer necessary; the casts are hidden in the macros. some source files which depended on being able to define the old macro SYSCALL_RETURNS_ERRNO have been modified to directly use __syscall() instead of syscall(). references to SYSCALL_SIGSET_SIZE and SYSCALL_LL have also been changed. x86_64 has not been tested, and may need a follow-up commit to fix any minor bugs/oversights. 2011-03-19 21:36:10 -04:00			`ret = syscall(__NR_rt_sigtimedwait, mask, si, timeout, 8);`
overhaul cancellation to fix resource leaks and dangerous behavior with signals this commit addresses two issues: 1. a race condition, whereby a cancellation request occurring after a syscall returned from kernelspace but before the subsequent CANCELPT_END would cause cancellable resource-allocating syscalls (like open) to leak resources. 2. signal handlers invoked while the thread was blocked at a cancellation point behaved as if asynchronous cancellation mode wer in effect, resulting in potentially dangerous state corruption if a cancellation request occurs. the glibc/nptl implementation of threads shares both of these issues. with this commit, both are fixed. however, cancellation points encountered in a signal handler will not be acted upon if the signal was received while the thread was already at a cancellation point. they will of course be acted upon after the signal handler returns, so in real-world usage where signal handlers quickly return, it should not be a problem. it's possible to solve this problem too by having sigaction() wrap all signal handlers with a function that uses a pthread_cleanup handler to catch cancellation, patch up the saved context, and return into the cancellable function that will catch and act upon the cancellation. however that would be a lot of complexity for minimal if any benefit... 2011-03-24 14:18:00 -04:00			`if (ret<0) CANCELPT_TRY;`
don't fail with EINTR in sigtimedwait POSIX allows either behavior, but sigwait is not allowed to fail with EINTR, so the retry loop would have to be in one or the other anyway. 2011-03-10 10:43:09 -05:00			`} while (ret<0 && errno==EINTR);`
make sigtimedwait a cancellation point 2011-03-10 10:59:50 -05:00			`CANCELPT_END;`
don't fail with EINTR in sigtimedwait POSIX allows either behavior, but sigwait is not allowed to fail with EINTR, so the retry loop would have to be in one or the other anyway. 2011-03-10 10:43:09 -05:00			`return ret;`
initial check-in, version 0.5.0 2011-02-12 00:22:29 -05:00			`}`