pthread stack treatment overhaul for application-provided stacks, etc.

[musl] / src / thread / pthread_create.c

diff --git a/src/thread/pthread_create.c b/src/thread/pthread_create.c
index a65e88e..4c1deca 100644 (file)
--- a/src/thread/pthread_create.c
+++ b/src/thread/pthread_create.c
@@ -96,15 +96,15 @@ 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;
        unsigned flags = 0x7d8f00;
        int do_sched = 0;
+       pthread_attr_t attr = {0};
 
        if (!self) return ENOSYS;
        if (!libc.threaded) {
@@ -115,19 +115,31 @@ 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);
+               /* 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;
@@ -140,8 +152,10 @@ int pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict attr,
                        if (map == MAP_FAILED) return EAGAIN;
                }
                tsd = map + size - __pthread_tsd_size;
+               if (!stack) stack = tsd - libc.tls_size;
        }
-       new = __copy_tls(stack = tsd - libc.tls_size);
+
+       new = __copy_tls(tsd - libc.tls_size);
        new->map_base = map;
        new->map_size = size;
        new->pid = self->pid;
@@ -150,11 +164,11 @@ int pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict attr,
        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);
@@ -180,7 +194,7 @@ int pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict attr,
 
        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;