X-Git-Url: http://nsz.repo.hu/git/?p=musl;a=blobdiff_plain;f=src%2Fthread%2Fpthread_create.c;h=6c841be799b1632917c4b318dc0fa8faf4bd3e3a;hp=a65e88e153e90514c6e21e43af1a1f9974d99bbf;hb=HEAD;hpb=1e21e78bf7a5c24c217446d8760be7b7188711c2

diff --git a/src/thread/pthread_create.c b/src/thread/pthread_create.c
index a65e88e1..6c841be7 100644
--- a/src/thread/pthread_create.c
+++ b/src/thread/pthread_create.c
@@ -12,7 +12,7 @@ weak_alias(dummy_0, __pthread_tsd_run_dtors);
 _Noreturn void pthread_exit(void *result)
 {
 	pthread_t self = pthread_self();
-	int n;
+	sigset_t set;
 
 	self->result = result;
 
@@ -30,17 +30,43 @@ _Noreturn void pthread_exit(void *result)
 	/* Mark this thread dead before decrementing count */
 	__lock(self->killlock);
 	self->dead = 1;
+
+	/* 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. */
+	__block_all_sigs(&set);
+
+	/* Wait to unlock the kill lock, which governs functions like
+	 * pthread_kill which target a thread id, until signals have
+	 * been blocked. This precludes observation of the thread id
+	 * as a live thread (with application code running in it) after
+	 * the thread was reported dead by ESRCH being returned. */
 	__unlock(self->killlock);
 
-	do n = libc.threads_minus_1;
-	while (n && a_cas(&libc.threads_minus_1, n, n-1)!=n);
-	if (!n) exit(0);
+	/* 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;
+		__restore_sigs(&set);
+		exit(0);
+	}
 
 	if (self->detached && self->map_base) {
-		if (self->detached == 2)
-			__syscall(SYS_set_tid_address, 0);
-		__syscall(SYS_rt_sigprocmask, SIG_BLOCK,
-			SIGALL_SET, 0, __SYSCALL_SSLEN);
+		/* 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);
 	}
 
@@ -68,12 +94,11 @@ static int start(void *p)
 			self->detached = 2;
 			pthread_exit(0);
 		}
-		__syscall(SYS_rt_sigprocmask, SIG_SETMASK,
-			self->sigmask, 0, __SYSCALL_SSLEN);
+		__restore_sigs(self->sigmask);
 	}
 	if (self->unblock_cancel)
 		__syscall(SYS_rt_sigprocmask, SIG_UNBLOCK,
-			SIGPT_SET, 0, __SYSCALL_SSLEN);
+			SIGPT_SET, 0, _NSIG/8);
 	pthread_exit(self->start(self->start_arg));
 	return 0;
 }
@@ -96,15 +121,15 @@ static void init_file_lock(FILE *f)
 
 void *__copy_tls(unsigned char *);
 
-int pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict attr, void *(*entry)(void *), void *restrict arg)
+int pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict attrp, void *(*entry)(void *), void *restrict arg)
 {
 	int ret;
-	size_t size = DEFAULT_STACK_SIZE + DEFAULT_GUARD_SIZE;
-	size_t guard = DEFAULT_GUARD_SIZE;
+	size_t size, guard;
 	struct pthread *self = pthread_self(), *new;
-	unsigned char *map, *stack, *tsd;
+	unsigned char *map = 0, *stack = 0, *tsd = 0, *stack_limit;
 	unsigned flags = 0x7d8f00;
 	int do_sched = 0;
+	pthread_attr_t attr = {0};
 
 	if (!self) return ENOSYS;
 	if (!libc.threaded) {
@@ -115,49 +140,68 @@ int pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict attr,
 		init_file_lock(__stderr_used);
 		libc.threaded = 1;
 	}
+	if (attrp) attr = *attrp;
 
 	__acquire_ptc();
 
-	if (attr && attr->_a_stackaddr) {
-		map = 0;
-		tsd = (void *)(attr->_a_stackaddr-__pthread_tsd_size & -16);
-	} else {
-		if (attr) {
-			guard = ROUND(attr->_a_guardsize + DEFAULT_GUARD_SIZE);
-			size = guard + ROUND(attr->_a_stacksize
-				+ DEFAULT_STACK_SIZE + libc.tls_size);
+	if (attr._a_stackaddr) {
+		size_t need = libc.tls_size + __pthread_tsd_size;
+		size = attr._a_stacksize + DEFAULT_STACK_SIZE;
+		stack = (void *)(attr._a_stackaddr & -16);
+		stack_limit = (void *)(attr._a_stackaddr - size);
+		/* Use application-provided stack for TLS only when
+		 * it does not take more than ~12% or 2k of the
+		 * application's stack space. */
+		if (need < size/8 && need < 2048) {
+			tsd = stack - __pthread_tsd_size;
+			stack = tsd - libc.tls_size;
+		} else {
+			size = ROUND(need);
+			guard = 0;
 		}
-		size += __pthread_tsd_size;
+	} else {
+		guard = ROUND(DEFAULT_GUARD_SIZE + attr._a_guardsize);
+		size = guard + ROUND(DEFAULT_STACK_SIZE + attr._a_stacksize
+			+ libc.tls_size +  __pthread_tsd_size);
+	}
+
+	if (!tsd) {
 		if (guard) {
 			map = mmap(0, size, PROT_NONE, MAP_PRIVATE|MAP_ANON, -1, 0);
-			if (map == MAP_FAILED) return EAGAIN;
+			if (map == MAP_FAILED) goto fail;
 			if (mprotect(map+guard, size-guard, PROT_READ|PROT_WRITE)) {
 				munmap(map, size);
-				return EAGAIN;
+				goto fail;
 			}
 		} else {
 			map = mmap(0, size, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON, -1, 0);
-			if (map == MAP_FAILED) return EAGAIN;
+			if (map == MAP_FAILED) goto fail;
 		}
 		tsd = map + size - __pthread_tsd_size;
+		if (!stack) {
+			stack = tsd - libc.tls_size;
+			stack_limit = map + guard;
+		}
 	}
-	new = __copy_tls(stack = tsd - libc.tls_size);
+
+	new = __copy_tls(tsd - libc.tls_size);
 	new->map_base = map;
 	new->map_size = size;
+	new->stack = stack;
+	new->stack_size = stack - stack_limit;
 	new->pid = self->pid;
 	new->errno_ptr = &new->errno_val;
 	new->start = entry;
 	new->start_arg = arg;
 	new->self = new;
 	new->tsd = (void *)tsd;
-	if (attr && attr->_a_detach) {
+	if (attr._a_detach) {
 		new->detached = 1;
 		flags -= 0x200000;
 	}
-	if (attr && attr->_a_sched) {
+	if (attr._a_sched) {
 		do_sched = new->startlock[0] = 1;
-		__syscall(SYS_rt_sigprocmask, SIG_BLOCK,
-			SIGALL_SET, self->sigmask, __SYSCALL_SSLEN);
+		__block_app_sigs(new->sigmask);
 	}
 	new->unblock_cancel = self->cancel;
 	new->canary = self->canary;
@@ -168,19 +212,18 @@ int pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict attr,
 	__release_ptc();
 
 	if (do_sched) {
-		__syscall(SYS_rt_sigprocmask, SIG_SETMASK,
-			new->sigmask, 0, __SYSCALL_SSLEN);
+		__restore_sigs(new->sigmask);
 	}
 
 	if (ret < 0) {
 		a_dec(&libc.threads_minus_1);
-		munmap(map, size);
+		if (map) munmap(map, size);
 		return EAGAIN;
 	}
 
 	if (do_sched) {
 		ret = __syscall(SYS_sched_setscheduler, new->tid,
-			attr->_a_policy, &attr->_a_prio);
+			attr._a_policy, &attr._a_prio);
 		a_store(new->startlock, ret<0 ? 2 : 0);
 		__wake(new->startlock, 1, 1);
 		if (ret < 0) return -ret;
@@ -188,4 +231,7 @@ int pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict attr,
 
 	*res = new;
 	return 0;
+fail:
+	__release_ptc();
+	return EAGAIN;
 }