| Message ID | 20180411163940.2523-17-kwolf@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | Drain fixes and cleanups, part 3 | expand |
On 11/04/2018 18:39, Kevin Wolf wrote: > 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(-) > > diff --git a/include/block/aio-wait.h b/include/block/aio-wait.h > index 783d3678dd..c85a62f798 100644 > --- a/include/block/aio-wait.h > +++ b/include/block/aio-wait.h > @@ -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); \ > Looks good. Paolo
diff --git a/include/block/aio-wait.h b/include/block/aio-wait.h index 783d3678dd..c85a62f798 100644 --- a/include/block/aio-wait.h +++ b/include/block/aio-wait.h @@ -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(-)