Commit 4d22bbf4 authored by Kevin Wolf's avatar Kevin Wolf
Browse files

block: Allow AIO_WAIT_WHILE with NULL ctx 



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: default avatarKevin Wolf <kwolf@redhat.com>
parent 57320ca9

include/block/aio-wait.h

+9 −4
Original line number Diff line number Diff line
@@ -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)) {                                           \

            if (ctx_) {                                            \

                aio_context_release(ctx_);                         \

            }                                                      \

            aio_poll(qemu_get_aio_context(), true);                \

            if (ctx_) {                                            \

                aio_context_acquire(ctx_);                         \

            }                                                      \

            waited_ = true;                                        \

        }                                                          \

        atomic_dec(&wait_->num_waiters);                           \