# HG changeset patch
# User Piotr Sikora <piotrsik...@google.com>
# Date 1471265532 25200
# Mon Aug 15 05:52:12 2016 -0700
# Node ID 40765d8ee4dd29089b0e60ed5b6099ac624e804e
# Parent 2f2ec92c3af93c11e195fb6d805df57518fede7c
Core: add ngx_atomic_store() and ngx_atomic_load().
Those functions must be used to prevent data races between
threads operating concurrently on the same variables.
No performance loss measured in microbenchmarks on x86_64.
No binary changes when compiled without __atomic intrinsics.
Found with ThreadSanitizer.
Signed-off-by: Piotr Sikora <piotrsik...@google.com>
diff -r 2f2ec92c3af9 -r 40765d8ee4dd auto/cc/conf
--- a/auto/cc/conf
+++ b/auto/cc/conf
@@ -178,7 +178,7 @@ if [ "$NGX_PLATFORM" != win32 ]; then
fi
- ngx_feature="gcc builtin atomic operations"
+ ngx_feature="gcc builtin __sync operations"
ngx_feature_name=NGX_HAVE_GCC_ATOMIC
ngx_feature_run=yes
ngx_feature_incs=
@@ -195,6 +195,19 @@ if [ "$NGX_PLATFORM" != win32 ]; then
. auto/feature
+ ngx_feature="gcc builtin __atomic operations"
+ ngx_feature_name=NGX_HAVE_GCC_ATOMIC_STORE_AND_LOAD
+ ngx_feature_run=yes
+ ngx_feature_incs=
+ ngx_feature_path=
+ ngx_feature_libs=
+ ngx_feature_test="long n = 0;
+ __atomic_store_n(&n, 1, __ATOMIC_RELEASE);
+ if (__atomic_load_n(&n, __ATOMIC_ACQUIRE) != 1)
+ return 1"
+ . auto/feature
+
+
if [ "$NGX_CC_NAME" = "ccc" ]; then
echo "checking for C99 variadic macros ... disabled"
else
diff -r 2f2ec92c3af9 -r 40765d8ee4dd src/core/ngx_rwlock.c
--- a/src/core/ngx_rwlock.c
+++ b/src/core/ngx_rwlock.c
@@ -53,7 +53,7 @@ ngx_rwlock_rlock(ngx_atomic_t *lock)
ngx_atomic_uint_t readers;
for ( ;; ) {
- readers = *lock;
+ readers = ngx_atomic_load(lock);
if (readers != NGX_RWLOCK_WLOCK
&& ngx_atomic_cmp_set(lock, readers, readers + 1))
@@ -69,7 +69,7 @@ ngx_rwlock_rlock(ngx_atomic_t *lock)
ngx_cpu_pause();
}
- readers = *lock;
+ readers = ngx_atomic_load(lock);
if (readers != NGX_RWLOCK_WLOCK
&& ngx_atomic_cmp_set(lock, readers, readers + 1))
@@ -89,10 +89,10 @@ ngx_rwlock_unlock(ngx_atomic_t *lock)
{
ngx_atomic_uint_t readers;
- readers = *lock;
+ readers = ngx_atomic_load(lock);
if (readers == NGX_RWLOCK_WLOCK) {
- *lock = 0;
+ ngx_atomic_store(lock, 0);
return;
}
@@ -102,7 +102,7 @@ ngx_rwlock_unlock(ngx_atomic_t *lock)
return;
}
- readers = *lock;
+ readers = ngx_atomic_load(lock);
}
}
diff -r 2f2ec92c3af9 -r 40765d8ee4dd src/core/ngx_shmtx.c
--- a/src/core/ngx_shmtx.c
+++ b/src/core/ngx_shmtx.c
@@ -171,7 +171,7 @@ ngx_shmtx_wakeup(ngx_shmtx_t *mtx)
for ( ;; ) {
- wait = *mtx->wait;
+ wait = ngx_atomic_load(mtx->wait);
if ((ngx_atomic_int_t) wait <= 0) {
return;
diff -r 2f2ec92c3af9 -r 40765d8ee4dd src/core/ngx_thread_pool.c
--- a/src/core/ngx_thread_pool.c
+++ b/src/core/ngx_thread_pool.c
@@ -164,9 +164,9 @@ ngx_thread_pool_init(ngx_thread_pool_t *
static void
ngx_thread_pool_destroy(ngx_thread_pool_t *tp)
{
- ngx_uint_t n;
- ngx_thread_task_t task;
- volatile ngx_uint_t lock;
+ ngx_uint_t n;
+ ngx_atomic_t lock;
+ ngx_thread_task_t task;
ngx_memzero(&task, sizeof(ngx_thread_task_t));
@@ -174,13 +174,13 @@ ngx_thread_pool_destroy(ngx_thread_pool_
task.ctx = (void *) &lock;
for (n = 0; n < tp->threads; n++) {
- lock = 1;
+ ngx_atomic_store(&lock, 1);
if (ngx_thread_task_post(tp, &task) != NGX_OK) {
return;
}
- while (lock) {
+ while (ngx_atomic_load(&lock) != 0) {
ngx_sched_yield();
}
@@ -196,9 +196,9 @@ ngx_thread_pool_destroy(ngx_thread_pool_
static void
ngx_thread_pool_exit_handler(void *data, ngx_log_t *log)
{
- ngx_uint_t *lock = data;
+ ngx_atomic_uint_t *lock = data;
- *lock = 0;
+ ngx_atomic_store(lock, 0);
pthread_exit(0);
}
diff -r 2f2ec92c3af9 -r 40765d8ee4dd src/os/unix/ngx_atomic.h
--- a/src/os/unix/ngx_atomic.h
+++ b/src/os/unix/ngx_atomic.h
@@ -304,12 +304,25 @@ ngx_atomic_fetch_add(ngx_atomic_t *value
#endif
+#if (NGX_HAVE_GCC_ATOMIC_STORE_AND_LOAD)
+
+#define ngx_atomic_store(x, value) __atomic_store_n(x, value,
__ATOMIC_RELEASE)
+#define ngx_atomic_load(x) __atomic_load_n(x, __ATOMIC_ACQUIRE)
+
+#else
+
+#define ngx_atomic_store(x, value) *(x) = value
+#define ngx_atomic_load(x) *(x)
+
+#endif
+
+
void ngx_spinlock(ngx_atomic_t *lock, ngx_atomic_int_t value, ngx_uint_t spin);
#define ngx_trylock(lock, value) \
- (*(lock) == 0 && ngx_atomic_cmp_set(lock, 0, value))
+ (ngx_atomic_load(lock) == 0 && ngx_atomic_cmp_set(lock, 0, value))
-#define ngx_unlock(lock) *(lock) = 0
+#define ngx_unlock(lock) ngx_atomic_store(lock, 0)
#endif /* _NGX_ATOMIC_H_INCLUDED_ */
diff -r 2f2ec92c3af9 -r 40765d8ee4dd src/os/win32/ngx_atomic.h
--- a/src/os/win32/ngx_atomic.h
+++ b/src/os/win32/ngx_atomic.h
@@ -60,12 +60,16 @@ typedef volatile ngx_atomic_uint_t ngx_
#endif
+#define ngx_atomic_store(x, value) *(x) = value
+#define ngx_atomic_load(x) *(x)
+
+
void ngx_spinlock(ngx_atomic_t *lock, ngx_atomic_int_t value, ngx_uint_t spin);
#define ngx_trylock(lock, value) \
- (*(lock) == 0 && ngx_atomic_cmp_set(lock, 0, value))
+ (ngx_atomic_load(lock) == 0 && ngx_atomic_cmp_set(lock, 0, value))
-#define ngx_unlock(lock) *(lock) = 0
+#define ngx_unlock(lock) ngx_atomic_store(lock, 0)
#endif /* _NGX_ATOMIC_H_INCLUDED_ */
_______________________________________________
nginx-devel mailing list
nginx-devel@nginx.org
http://mailman.nginx.org/mailman/listinfo/nginx-devel
