From b470030f839a375e5030ec9d44903ef7581c15a2 Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Thu, 24 Mar 2011 14:18:00 -0400 Subject: 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... --- src/time/nanosleep.c | 1 + 1 file changed, 1 insertion(+) (limited to 'src/time/nanosleep.c') diff --git a/src/time/nanosleep.c b/src/time/nanosleep.c index 2f65762f..0e0753f3 100644 --- a/src/time/nanosleep.c +++ b/src/time/nanosleep.c @@ -8,6 +8,7 @@ int nanosleep(const struct timespec *req, struct timespec *rem) int ret; CANCELPT_BEGIN; ret = syscall(SYS_nanosleep, req, rem); + CANCELPT_TRY; CANCELPT_END; return ret; } -- cgit v1.2.1