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add comments on some of the pthread_exit logic

This commit is contained in:
Rich Felker 2013-04-26 16:04:30 -04:00
parent 23f21c304f
commit 6e531f999a
1 changed files with 15 additions and 2 deletions
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17
src/thread/pthread_create.c
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@ -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);
}