fix pthread_detach inadvertently acting as cancellation point in race case

[musl] / src / thread / pthread_barrier_wait.c

diff --git a/src/thread/pthread_barrier_wait.c b/src/thread/pthread_barrier_wait.c
index 6052925..cc2a8bb 100644 (file)
--- a/src/thread/pthread_barrier_wait.c
+++ b/src/thread/pthread_barrier_wait.c
@@ -1,23 +1,5 @@
 #include "pthread_impl.h"
 
-static int vmlock[2];
-
-void __vm_lock(int inc)
-{
-       for (;;) {
-               int v = vmlock[0];
-               if (inc*v < 0) __wait(vmlock, vmlock+1, v, 1);
-               else if (a_cas(vmlock, v, v+inc)==v) break;
-       }
-}
-
-void __vm_unlock(void)
-{
-       int inc = vmlock[0]>0 ? -1 : 1;
-       if (a_fetch_add(vmlock, inc)==-inc && vmlock[1])
-               __wake(vmlock, -1, 1);
-}
-
 static int pshared_barrier_wait(pthread_barrier_t *b)
 {
        int limit = (b->_b_limit & INT_MAX) + 1;
@@ -41,7 +23,7 @@ static int pshared_barrier_wait(pthread_barrier_t *b)
                        __wait(&b->_b_count, &b->_b_waiters2, v, 0);
        }
 
-       __vm_lock(+1);
+       __vm_lock();
 
        /* Ensure all threads have a vm lock before proceeding */
        if (a_fetch_add(&b->_b_count, -1)==1-limit) {
@@ -69,10 +51,10 @@ static int pshared_barrier_wait(pthread_barrier_t *b)
 
 struct instance
 {
-       int count;
-       int last;
-       int waiters;
-       int finished;
+       volatile int count;
+       volatile int last;
+       volatile int waiters;
+       volatile int finished;
 };
 
 int pthread_barrier_wait(pthread_barrier_t *b)
@@ -94,7 +76,7 @@ int pthread_barrier_wait(pthread_barrier_t *b)
        /* First thread to enter the barrier becomes the "instance owner" */
        if (!inst) {
                struct instance new_inst = { 0 };
-               int spins = 10000;
+               int spins = 200;
                b->_b_inst = inst = &new_inst;
                a_store(&b->_b_lock, 0);
                if (b->_b_waiters) __wake(&b->_b_lock, 1, 1);
@@ -102,7 +84,8 @@ int pthread_barrier_wait(pthread_barrier_t *b)
                        a_spin();
                a_inc(&inst->finished);
                while (inst->finished == 1)
-                       __syscall(SYS_futex, &inst->finished, FUTEX_WAIT,1,0);
+                       __syscall(SYS_futex,&inst->finished,FUTEX_WAIT|FUTEX_PRIVATE,1,0) != -ENOSYS
+                       || __syscall(SYS_futex,&inst->finished,FUTEX_WAIT,1,0);
                return PTHREAD_BARRIER_SERIAL_THREAD;
        }