On 03/07/2018 06:46 AM, Stefan Hajnoczi wrote:
Nested BDRV_POLL_WHILE() calls can occur. Currently
assert(!wait_->wakeup) fails in AIO_WAIT_WHILE() when this happens.
This patch converts the bool wait_->need_kick flag to an unsigned
wait_->num_waiters counter.
Nesting works correctly because outer AIO_WAIT_WHILE() callers evaluate
the condition again after the inner caller completes (invoking the inner
caller counts as aio_poll() progress).
Reported-by: "fuweiwei (C)" <fuweiw...@huawei.com>
Cc: Paolo Bonzini <pbonz...@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
---
v2:
* Rebase onto qemu.git/master now that AIO_WAIT_WHILE() has landed
[Kevin]
include/block/aio-wait.h | 61 ++++++++++++++++++++++++------------------------
Looks big due to whitespace change when column for trailing \ changed.
Viewing the diff with whitespace ignored made it easier to review.
Reviewed-by: Eric Blake <ebl...@redhat.com>
diff --git c/include/block/aio-wait.h w/include/block/aio-wait.h
index a48c744fa87..74cde07bef3 100644
--- c/include/block/aio-wait.h
+++ w/include/block/aio-wait.h
@@ -50,8 +50,8 @@
* }
*/
typedef struct {
- /* Is the main loop waiting for a kick? Accessed with atomic ops. */
- bool need_kick;
+ /* Number of waiting AIO_WAIT_WHILE() callers. Accessed with atomic
ops. */
+ unsigned num_waiters;
} AioWait;
/**
@@ -84,9 +84,8 @@ typedef struct {
} else { \
assert(qemu_get_current_aio_context() == \
qemu_get_aio_context()); \
- assert(!wait_->need_kick); \
- /* Set wait_->need_kick before evaluating cond. */ \
- atomic_mb_set(&wait_->need_kick, true); \
+ /* Increment wait_->num_waiters before evaluating cond. */ \
+ atomic_inc(&wait_->num_waiters); \
while (busy_) { \
if ((cond)) { \
waited_ = busy_ = true; \
@@ -98,7 +97,7 @@ typedef struct {
waited_ |= busy_; \
} \
} \
- atomic_set(&wait_->need_kick, false); \
+ atomic_dec(&wait_->num_waiters); \
} \
waited_; })
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
