make last thread's pthread_exit give exit(0) a consistent state

the previous few commits ended up leaving the thread count and signal
mask wrong for atexit handlers and stdio cleanup.

diff --git a/src/thread/pthread_create.c b/src/thread/pthread_create.c
index 0567f966e02d26fbfc366631af9919e20ce7378c..5d5d3a6f939a84548faab354f970556109bec107 100644 (file)
--- a/src/thread/pthread_create.c
+++ b/src/thread/pthread_create.c
@@ -12,6 +12,7 @@ weak_alias(dummy_0, __pthread_tsd_run_dtors);
 _Noreturn void pthread_exit(void *result)
 {
        pthread_t self = pthread_self();
+       sigset_t set;
 
        self->result = result;
 
@@ -35,9 +36,18 @@ _Noreturn void pthread_exit(void *result)
         * 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);
-
-       if (a_fetch_add(&libc.threads_minus_1, -1)==0) exit(0);
+       __syscall(SYS_rt_sigprocmask, SIG_BLOCK, SIGALL_SET, &set, _NSIG/8);
+
+       /* It's impossible to determine whether this is "the last thread"
+        * until performing the atomic decrement, since multiple threads
+        * could exit at the same time. For the last thread, revert the
+        * decrement and unblock signals to give the atexit handlers and
+        * stdio cleanup code a consistent state. */
+       if (a_fetch_add(&libc.threads_minus_1, -1)==0) {
+               libc.threads_minus_1 = 0;
+               __syscall(SYS_rt_sigprocmask, SIG_SETMASK, &set, 0, _NSIG/8);
+               exit(0);
+       }
 
        if (self->detached && self->map_base) {
                /* Detached threads must avoid the kernel clear_child_tid