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authorRich Felker <dalias@aerifal.cx>2013-04-26 16:04:30 -0400
committerRich Felker <dalias@aerifal.cx>2013-04-26 16:04:30 -0400
commit6e531f999a82cf39a951e1e9bba3cb80a6eb1464 (patch)
treec17563fb2d6210fb8b513b0c968e4ad5bfcf02d0
parent23f21c304fd6a7592b70927e247129c5a2bc2390 (diff)
downloadmusl-6e531f999a82cf39a951e1e9bba3cb80a6eb1464.tar.gz
add comments on some of the pthread_exit logic
-rw-r--r--src/thread/pthread_create.c17
1 files changed, 15 insertions, 2 deletions
diff --git a/src/thread/pthread_create.c b/src/thread/pthread_create.c
index 0cd2d6c2..6a37ee9b 100644
--- a/src/thread/pthread_create.c
+++ b/src/thread/pthread_create.c
@@ -32,6 +32,10 @@ _Noreturn void pthread_exit(void *result)
self->dead = 1;
__unlock(self->killlock);
+ /* Block all signals before decrementing the live thread count.
+ * This is important to ensure that dynamically allocated TLS
+ * is not under-allocated/over-committed, and possibly for other
+ * reasons as well. */
__syscall(SYS_rt_sigprocmask, SIG_BLOCK, SIGALL_SET, 0, _NSIG/8);
do n = libc.threads_minus_1;
@@ -39,8 +43,17 @@ _Noreturn void pthread_exit(void *result)
if (!n) exit(0);
if (self->detached && self->map_base) {
- if (self->detached == 2)
- __syscall(SYS_set_tid_address, 0);
+ /* Detached threads must avoid the kernel clear_child_tid
+ * feature, since the virtual address will have been
+ * unmapped and possibly already reused by a new mapping
+ * at the time the kernel would perform the write. In
+ * the case of threads that started out detached, the
+ * initial clone flags are correct, but if the thread was
+ * detached later (== 2), we need to clear it here. */
+ if (self->detached == 2) __syscall(SYS_set_tid_address, 0);
+
+ /* The following call unmaps the thread's stack mapping
+ * and then exits without touching the stack. */
__unmapself(self->map_base, self->map_size);
}