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authorRich Felker <dalias@aerifal.cx>2011-03-24 14:18:00 -0400
committerRich Felker <dalias@aerifal.cx>2011-03-24 14:18:00 -0400
commitb470030f839a375e5030ec9d44903ef7581c15a2 (patch)
tree462b1df89a3ea45bcf50b9d0a844472576ed6585 /src/thread/pthread_cond_timedwait.c
parent095820016689dfdc9141f477a86de22054c86078 (diff)
downloadmusl-b470030f839a375e5030ec9d44903ef7581c15a2.tar.gz
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...
Diffstat (limited to 'src/thread/pthread_cond_timedwait.c')
-rw-r--r--src/thread/pthread_cond_timedwait.c10
1 files changed, 6 insertions, 4 deletions
diff --git a/src/thread/pthread_cond_timedwait.c b/src/thread/pthread_cond_timedwait.c
index 228f61f7..1439aace 100644
--- a/src/thread/pthread_cond_timedwait.c
+++ b/src/thread/pthread_cond_timedwait.c
@@ -8,19 +8,21 @@ static void relock(void *m)
int pthread_cond_timedwait(pthread_cond_t *c, pthread_mutex_t *m, const struct timespec *ts)
{
int r, e=0;
- CANCELPT(0);
+ CANCELPT_BEGIN;
+ CANCELPT_END;
pthread_cleanup_push(relock, m);
c->_c_block = 1;
if ((r=pthread_mutex_unlock(m))) return r;
- CANCELPT(1);
+ CANCELPT_BEGIN;
e = __timedwait(&c->_c_block, 1, c->_c_clock, ts, 0);
- CANCELPT(0);
+ CANCELPT_END;
pthread_cleanup_pop(0);
if ((r=pthread_mutex_lock(m))) return r;
- CANCELPT(0);
+ CANCELPT_BEGIN;
+ CANCELPT_END;
return e;
}