[Qemu-devel] [RFC PATCH 4/4] tsan: various fixes for make check

["Alex Bennée" <alex.bennee@linaro.org>]

After building with the ThreadSanitizer I ran make check and started
going through the failures reported. Most are failures to use atomic
primitives to access variables previously atomically set. While this
likely will work on x86 it could cause problems on other architectures.

 - async: use atomic reads for scheduled/notify_me
 - thread-pool: use atomic_mb_read/set to for thread ->state
 - test-thread-pool: use atomic read for data.n

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
---
 async.c                  | 4 ++--
 tests/test-thread-pool.c | 2 +-
 thread-pool.c            | 9 ++++-----
 3 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/async.c b/async.c
index e106072..8d5f810 100644
--- a/async.c
+++ b/async.c
@@ -165,7 +165,7 @@ aio_compute_timeout(AioContext *ctx)
     QEMUBH *bh;
 
     for (bh = ctx->first_bh; bh; bh = bh->next) {
-        if (!bh->deleted && bh->scheduled) {
+        if (!bh->deleted && atomic_read(&bh->scheduled)) {
             if (bh->idle) {
                 /* idle bottom halves will be polled at least
                  * every 10ms */
@@ -286,7 +286,7 @@ void aio_notify(AioContext *ctx)
      * with atomic_or in aio_ctx_prepare or atomic_add in aio_poll.
      */
     smp_mb();
-    if (ctx->notify_me) {
+    if (atomic_read(&ctx->notify_me)) {
         event_notifier_set(&ctx->notifier);
         atomic_mb_set(&ctx->notified, true);
     }
diff --git a/tests/test-thread-pool.c b/tests/test-thread-pool.c
index ccdee39..5694ad9 100644
--- a/tests/test-thread-pool.c
+++ b/tests/test-thread-pool.c
@@ -46,7 +46,7 @@ static void test_submit(void)
 {
     WorkerTestData data = { .n = 0 };
     thread_pool_submit(pool, worker_cb, &data);
-    while (data.n == 0) {
+    while (atomic_read(&data.n) == 0) {
         aio_poll(ctx, true);
     }
     g_assert_cmpint(data.n, ==, 1);
diff --git a/thread-pool.c b/thread-pool.c
index 402c778..97b2c0c 100644
--- a/thread-pool.c
+++ b/thread-pool.c
@@ -99,15 +99,14 @@ static void *worker_thread(void *opaque)
 
         req = QTAILQ_FIRST(&pool->request_list);
         QTAILQ_REMOVE(&pool->request_list, req, reqs);
-        req->state = THREAD_ACTIVE;
+        atomic_mb_set(&req->state, THREAD_ACTIVE);
         qemu_mutex_unlock(&pool->lock);
 
         ret = req->func(req->arg);
 
         req->ret = ret;
         /* Write ret before state.  */
-        smp_wmb();
-        req->state = THREAD_DONE;
+        atomic_mb_set(&req->state, THREAD_DONE);
 
         qemu_mutex_lock(&pool->lock);
 
@@ -167,7 +166,7 @@ static void thread_pool_completion_bh(void *opaque)
 
 restart:
     QLIST_FOREACH_SAFE(elem, &pool->head, all, next) {
-        if (elem->state != THREAD_DONE) {
+        if (atomic_read(&elem->state) != THREAD_DONE) {
             continue;
         }
 
@@ -201,7 +200,7 @@ static void thread_pool_cancel(BlockAIOCB *acb)
     trace_thread_pool_cancel(elem, elem->common.opaque);
 
     qemu_mutex_lock(&pool->lock);
-    if (elem->state == THREAD_QUEUED &&
+    if (atomic_mb_read(&elem->state) == THREAD_QUEUED &&
         /* No thread has yet started working on elem. we can try to "steal"
          * the item from the worker if we can get a signal from the
          * semaphore.  Because this is non-blocking, we can do it with
-- 
2.7.0