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[v3,03/19] aio-wait: Increase num_waiters even in home thread

Message ID 20180920161958.27453-4-kwolf@redhat.com
State New
Headers show
Series Fix some jobs/drain/aio_poll related hangs | expand

Commit Message

Kevin Wolf Sept. 20, 2018, 4:19 p.m. UTC 
Even if AIO_WAIT_WHILE() is called in the home context of the
AioContext, we still want to allow the condition to change depending on
other threads as long as they kick the AioWait. Specfically block jobs
can be running in an I/O thread and should then be able to kick a drain
in the main loop context.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
---
 include/block/aio-wait.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)
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Patch

diff --git a/include/block/aio-wait.h b/include/block/aio-wait.h
index c85a62f798..600fad183e 100644
--- a/include/block/aio-wait.h
+++ b/include/block/aio-wait.h
@@ -76,6 +76,8 @@  typedef struct {
     bool waited_ = false;                                          \
     AioWait *wait_ = (wait);                                       \
     AioContext *ctx_ = (ctx);                                      \
+    /* Increment wait_->num_waiters before evaluating cond. */     \
+    atomic_inc(&wait_->num_waiters);                               \
     if (ctx_ && in_aio_context_home_thread(ctx_)) {                \
         while ((cond)) {                                           \
             aio_poll(ctx_, true);                                  \
@@ -84,8 +86,6 @@  typedef struct {
     } else {                                                       \
         assert(qemu_get_current_aio_context() ==                   \
                qemu_get_aio_context());                            \
-        /* Increment wait_->num_waiters before evaluating cond. */ \
-        atomic_inc(&wait_->num_waiters);                           \
         while ((cond)) {                                           \
             if (ctx_) {                                            \
                 aio_context_release(ctx_);                         \
@@ -96,8 +96,8 @@  typedef struct {
             }                                                      \
             waited_ = true;                                        \
         }                                                          \
-        atomic_dec(&wait_->num_waiters);                           \
     }                                                              \
+    atomic_dec(&wait_->num_waiters);                               \
     waited_; })
 
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