path: root/src/thread/pthread_self.c
diff options
authorRich Felker <>2014-03-24 16:57:11 -0400
committerRich Felker <>2014-03-24 16:57:11 -0400
commitdab441aea240f3b7c18a26d2ef51979ea36c301c (patch)
tree9bb6c68bc3b025020a15d0d92b2b6aeff84a4d8c /src/thread/pthread_self.c
parent98221c36119d2abfc55fe1d919705f625709fe3b (diff)
always initialize thread pointer at program start
this is the first step in an overhaul aimed at greatly simplifying and optimizing everything dealing with thread-local state. previously, the thread pointer was initialized lazily on first access, or at program startup if stack protector was in use, or at certain random places where inconsistent state could be reached if it were not initialized early. while believed to be fully correct, the logic was fragile and non-obvious. in the first phase of the thread pointer overhaul, support is retained (and in some cases improved) for systems/situation where loading the thread pointer fails, e.g. old kernels. some notes on specific changes: - the confusing use of libc.main_thread as an indicator that the thread pointer is initialized is eliminated in favor of an explicit has_thread_pointer predicate. - sigaction no longer needs to ensure that the thread pointer is initialized before installing a signal handler (this was needed to prevent a situation where the signal handler caused the thread pointer to be initialized and the subsequent sigreturn cleared it again) but it still needs to ensure that implementation-internal thread-related signals are not blocked. - pthread tsd initialization for the main thread is deferred in a new manner to minimize bloat in the static-linked __init_tp code. - pthread_setcancelstate no longer needs special handling for the situation before the thread pointer is initialized. it simply fails on systems that cannot support a thread pointer, which are non-conforming anyway. - pthread_cleanup_push/pop now check for missing thread pointer and nop themselves out in this case, so stdio no longer needs to avoid the cancellable path when the thread pointer is not available. a number of cases remain where certain interfaces may crash if the system does not support a thread pointer. at this point, these should be limited to pthread interfaces, and the number of such cases should be fewer than before.
Diffstat (limited to 'src/thread/pthread_self.c')
1 files changed, 1 insertions, 40 deletions
diff --git a/src/thread/pthread_self.c b/src/thread/pthread_self.c
index aed4b5f1..5f9e6516 100644
--- a/src/thread/pthread_self.c
+++ b/src/thread/pthread_self.c
@@ -1,45 +1,6 @@
#include "pthread_impl.h"
-static struct pthread *main_thread = &(struct pthread){0};
-/* pthread_key_create.c overrides this */
-static const void *dummy[1] = { 0 };
-weak_alias(dummy, __pthread_tsd_main);
-static int init_main_thread()
- __syscall(SYS_rt_sigprocmask, SIG_UNBLOCK,
- SIGPT_SET, 0, _NSIG/8);
- if (__set_thread_area(TP_ADJ(main_thread)) < 0) return -1;
- main_thread->canceldisable = libc.canceldisable;
- main_thread->tsd = (void **)__pthread_tsd_main;
- main_thread->errno_ptr = __errno_location();
- main_thread->self = main_thread;
- main_thread->tid = main_thread->pid =
- __syscall(SYS_set_tid_address, &main_thread->tid);
- if (!main_thread->dtv)
- main_thread->dtv = (void *)dummy;
- libc.main_thread = main_thread;
- return 0;
-pthread_t __pthread_self_def()
+pthread_t pthread_self()
- static int init, failed;
- if (!init) {
- if (failed) return 0;
- if (init_main_thread() < 0) failed = 1;
- if (failed) return 0;
- init = 1;
- }
return __pthread_self();
-weak_alias(__pthread_self_def, pthread_self);
-weak_alias(__pthread_self_def, __pthread_self_init);
-void *__install_initial_tls(void *p)
- main_thread = p;
- return __pthread_self_def();