musl/src/thread/pthread_kill.c

#include "pthread_impl.h"

int pthread_kill(pthread_t t, int sig)
{
	int r;
	__lock(&t->killlock);
	r = t->dead ? ESRCH : -__syscall(SYS_tgkill, t->pid, t->tid, sig);
	a_store(&t->killlock, 0);
	return r;
}
initial check-in, version 0.5.0 2011-02-12 00:22:29 -05:00			`#include "pthread_impl.h"`

			`int pthread_kill(pthread_t t, int sig)`
			`{`
fix race condition in pthread_kill if thread id was reused by the kernel between the time pthread_kill read it from the userspace pthread_t object and the time of the tgkill syscall, a signal could be sent to the wrong thread. the tgkill syscall was supposed to prevent this race (versus the old tkill syscall) but it can't; it can only help in the case where the tid is reused in a different process, but not when the tid is reused in the same process. the only solution i can see is an extra lock to prevent threads from exiting while another thread is trying to pthread_kill them. it should be very very cheap in the non-contended case. 2011-06-14 01:35:51 -04:00			`int r;`
			`__lock(&t->killlock);`
			`r = t->dead ? ESRCH : -__syscall(SYS_tgkill, t->pid, t->tid, sig);`
			`a_store(&t->killlock, 0);`
			`return r;`
initial check-in, version 0.5.0 2011-02-12 00:22:29 -05:00			`}`