path: root/src/signal
diff options
authorRich Felker <>2011-03-24 14:18:00 -0400
committerRich Felker <>2011-03-24 14:18:00 -0400
commitb470030f839a375e5030ec9d44903ef7581c15a2 (patch)
tree462b1df89a3ea45bcf50b9d0a844472576ed6585 /src/signal
parent095820016689dfdc9141f477a86de22054c86078 (diff)
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/signal')
2 files changed, 2 insertions, 0 deletions
diff --git a/src/signal/sigsuspend.c b/src/signal/sigsuspend.c
index 6c13fce1..9ee71240 100644
--- a/src/signal/sigsuspend.c
+++ b/src/signal/sigsuspend.c
@@ -7,6 +7,7 @@ int sigsuspend(const sigset_t *mask)
int ret;
ret = syscall(__NR_rt_sigsuspend, mask, 8);
+ if (ret<0) CANCELPT_TRY;
return ret;
diff --git a/src/signal/sigtimedwait.c b/src/signal/sigtimedwait.c
index a0edaaf3..86a2c879 100644
--- a/src/signal/sigtimedwait.c
+++ b/src/signal/sigtimedwait.c
@@ -9,6 +9,7 @@ int sigtimedwait(const sigset_t *mask, siginfo_t *si, const struct timespec *tim
do {
ret = syscall(__NR_rt_sigtimedwait, mask, si, timeout, 8);
+ if (ret<0) CANCELPT_TRY;
} while (ret<0 && errno==EINTR);
return ret;