@@ -57,7 +57,8 @@ typedef struct {
/**
* AIO_WAIT_WHILE:
* @wait: the aio wait object
- * @ctx: the aio context
+ * @ctx: the aio context, or NULL if multiple aio contexts (for which the
+ * caller does not hold a lock) are involved in the polling condition.
* @cond: wait while this conditional expression is true
*
* Wait while a condition is true. Use this to implement synchronous
@@ -75,7 +76,7 @@ typedef struct {
bool waited_ = false; \
AioWait *wait_ = (wait); \
AioContext *ctx_ = (ctx); \
- if (in_aio_context_home_thread(ctx_)) { \
+ if (ctx_ && in_aio_context_home_thread(ctx_)) { \
while ((cond)) { \
aio_poll(ctx_, true); \
waited_ = true; \
@@ -86,9 +87,13 @@ typedef struct {
/* Increment wait_->num_waiters before evaluating cond. */ \
atomic_inc(&wait_->num_waiters); \
while ((cond)) { \
- aio_context_release(ctx_); \
+ if (ctx_) { \
+ aio_context_release(ctx_); \
+ } \
aio_poll(qemu_get_aio_context(), true); \
- aio_context_acquire(ctx_); \
+ if (ctx_) { \
+ aio_context_acquire(ctx_); \
+ } \
waited_ = true; \
} \
atomic_dec(&wait_->num_waiters); \
bdrv_drain_all() wants to have a single polling loop for draining the in-flight requests of all nodes. This means that the AIO_WAIT_WHILE() condition relies on activity in multiple AioContexts, which is polled from the mainloop context. We must therefore call AIO_WAIT_WHILE() from the mainloop thread and use the AioWait notification mechanism. Just randomly picking the AioContext of any non-mainloop thread would work, but instead of bothering to find such a context in the caller, we can just as well accept NULL for ctx. Signed-off-by: Kevin Wolf <kwolf@redhat.com> --- include/block/aio-wait.h | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-)