fix deletion of pthread tsd keys that still have non-null values stored

[musl] / src / thread / pthread_key_create.c

diff --git a/src/thread/pthread_key_create.c b/src/thread/pthread_key_create.c
index c29935c..e26f199 100644 (file)
--- a/src/thread/pthread_key_create.c
+++ b/src/thread/pthread_key_create.c
@@ -1,49 +1,125 @@
 #include "pthread_impl.h"
 
-const size_t __pthread_tsd_size = sizeof(void *) * PTHREAD_KEYS_MAX;
+volatile size_t __pthread_tsd_size = sizeof(void *) * PTHREAD_KEYS_MAX;
 void *__pthread_tsd_main[PTHREAD_KEYS_MAX] = { 0 };
 
 static void (*keys[PTHREAD_KEYS_MAX])(void *);
 
+static pthread_rwlock_t key_lock = PTHREAD_RWLOCK_INITIALIZER;
+
+static pthread_key_t next_key;
+
 static void nodtor(void *dummy)
 {
 }
 
-int pthread_key_create(pthread_key_t *k, void (*dtor)(void *))
+static void dirty(void *dummy)
+{
+}
+
+struct cleanup_args {
+       pthread_t caller;
+       int ret;
+};
+
+static void clean_dirty_tsd_callback(void *p)
+{
+       struct cleanup_args *args = p;
+       pthread_t self = __pthread_self();
+       pthread_key_t i;
+       for (i=0; i<PTHREAD_KEYS_MAX; i++) {
+               if (keys[i] == dirty && self->tsd[i])
+                       self->tsd[i] = 0;
+       }
+       /* Arbitrary choice to avoid data race. */
+       if (args->caller == self) args->ret = 0;
+}
+
+static int clean_dirty_tsd(void)
+{
+       struct cleanup_args args = {
+               .caller = __pthread_self(),
+               .ret = EAGAIN
+       };
+       __pthread_key_delete_synccall(clean_dirty_tsd_callback, &args);
+       return args.ret;
+}
+
+int __pthread_key_create(pthread_key_t *k, void (*dtor)(void *))
 {
-       unsigned i = (uintptr_t)&k / 16 % PTHREAD_KEYS_MAX;
-       unsigned j = i;
+       pthread_key_t j = next_key;
+       pthread_t self = __pthread_self();
+       int found_dirty = 0;
 
-       __pthread_self_init();
+       /* This can only happen in the main thread before
+        * pthread_create has been called. */
+       if (!self->tsd) self->tsd = __pthread_tsd_main;
+
+       /* Purely a sentinel value since null means slot is free. */
        if (!dtor) dtor = nodtor;
+
+       pthread_rwlock_wrlock(&key_lock);
        do {
-               if (!a_cas_p(keys+j, 0, (void *)dtor)) {
-                       *k = j;
+               if (!keys[j]) {
+                       keys[next_key = *k = j] = dtor;
+                       pthread_rwlock_unlock(&key_lock);
                        return 0;
+               } else if (keys[j] == dirty) {
+                       found_dirty = 1;
                }
-       } while ((j=(j+1)%PTHREAD_KEYS_MAX) != i);
-       return EAGAIN;
+       } while ((j=(j+1)%PTHREAD_KEYS_MAX) != next_key);
+
+       /* It's possible that all slots are in use or __synccall fails. */
+       if (!found_dirty || clean_dirty_tsd()) {
+               pthread_rwlock_unlock(&key_lock);
+               return EAGAIN;
+       }
+
+       /* If this point is reached there is necessarily a newly-cleaned
+        * slot to allocate to satisfy the caller's request. Find it and
+        * mark any additional previously-dirty slots clean. */
+       for (j=0; j<PTHREAD_KEYS_MAX; j++) {
+               if (keys[j] == dirty) {
+                       if (dtor) {
+                               keys[next_key = *k = j] = dtor;
+                               dtor = 0;
+                       } else {
+                               keys[j] = 0;
+                       }
+               }
+       }
+
+       pthread_rwlock_unlock(&key_lock);
+       return 0;
 }
 
-int pthread_key_delete(pthread_key_t k)
+int __pthread_key_delete_impl(pthread_key_t k)
 {
-       keys[k] = 0;
+       pthread_rwlock_wrlock(&key_lock);
+       keys[k] = dirty;
+       pthread_rwlock_unlock(&key_lock);
        return 0;
 }
 
 void __pthread_tsd_run_dtors()
 {
        pthread_t self = __pthread_self();
-       int i, j, not_finished = self->tsd_used;
-       for (j=0; not_finished && j<PTHREAD_DESTRUCTOR_ITERATIONS; j++) {
-               not_finished = 0;
+       int i, j;
+       for (j=0; self->tsd_used && j<PTHREAD_DESTRUCTOR_ITERATIONS; j++) {
+               pthread_rwlock_rdlock(&key_lock);
+               self->tsd_used = 0;
                for (i=0; i<PTHREAD_KEYS_MAX; i++) {
-                       if (self->tsd[i] && keys[i]) {
-                               void *tmp = self->tsd[i];
-                               self->tsd[i] = 0;
-                               keys[i](tmp);
-                               not_finished = 1;
+                       void *val = self->tsd[i];
+                       void (*dtor)(void *) = keys[i];
+                       self->tsd[i] = 0;
+                       if (val && dtor && dtor != nodtor && dtor != dirty) {
+                               pthread_rwlock_unlock(&key_lock);
+                               dtor(val);
+                               pthread_rwlock_rdlock(&key_lock);
                        }
                }
+               pthread_rwlock_unlock(&key_lock);
        }
 }
+
+weak_alias(__pthread_key_create, pthread_key_create);