diff options
author | Peter Maydell <peter.maydell@linaro.org> | 2020-08-21 17:26:52 +0100 |
---|---|---|
committer | Peter Maydell <peter.maydell@linaro.org> | 2020-08-21 17:26:52 +0100 |
commit | f86d9a093dada588889bde5582c7ec320487c4b8 (patch) | |
tree | e317d643fa35c79d98791bb1bd7fcc7f410557b6 /util | |
parent | d6f83a72a7db94a3ede9f5cc4fb39f9c8e89f954 (diff) | |
parent | 44277bf914471962c9e88e09c859aae65ae109c4 (diff) | |
download | qemu-f86d9a093dada588889bde5582c7ec320487c4b8.zip qemu-f86d9a093dada588889bde5582c7ec320487c4b8.tar.gz qemu-f86d9a093dada588889bde5582c7ec320487c4b8.tar.bz2 |
Merge remote-tracking branch 'remotes/stefanha/tags/block-pull-request' into staging
Pull request
# gpg: Signature made Mon 17 Aug 2020 15:34:34 BST
# gpg: using RSA key 8695A8BFD3F97CDAAC35775A9CA4ABB381AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>" [full]
# gpg: aka "Stefan Hajnoczi <stefanha@gmail.com>" [full]
# Primary key fingerprint: 8695 A8BF D3F9 7CDA AC35 775A 9CA4 ABB3 81AB 73C8
* remotes/stefanha/tags/block-pull-request:
aio-posix: keep aio_notify_me disabled during polling
async: always set ctx->notified in aio_notify()
async: rename event_notifier_dummy_cb/poll()
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Diffstat (limited to 'util')
-rw-r--r-- | util/aio-posix.c | 47 | ||||
-rw-r--r-- | util/async.c | 36 |
2 files changed, 48 insertions, 35 deletions
diff --git a/util/aio-posix.c b/util/aio-posix.c index 1b2a3af..f7f13eb 100644 --- a/util/aio-posix.c +++ b/util/aio-posix.c @@ -464,9 +464,6 @@ static bool remove_idle_poll_handlers(AioContext *ctx, int64_t now) * * Polls for a given time. * - * Note that ctx->notify_me must be non-zero so this function can detect - * aio_notify(). - * * Note that the caller must have incremented ctx->list_lock. * * Returns: true if progress was made, false otherwise @@ -476,7 +473,6 @@ static bool run_poll_handlers(AioContext *ctx, int64_t max_ns, int64_t *timeout) bool progress; int64_t start_time, elapsed_time; - assert(ctx->notify_me); assert(qemu_lockcnt_count(&ctx->list_lock) > 0); trace_run_poll_handlers_begin(ctx, max_ns, *timeout); @@ -520,8 +516,6 @@ static bool run_poll_handlers(AioContext *ctx, int64_t max_ns, int64_t *timeout) * @timeout: timeout for blocking wait, computed by the caller and updated if * polling succeeds. * - * ctx->notify_me must be non-zero so this function can detect aio_notify(). - * * Note that the caller must have incremented ctx->list_lock. * * Returns: true if progress was made, false otherwise @@ -556,6 +550,7 @@ bool aio_poll(AioContext *ctx, bool blocking) AioHandlerList ready_list = QLIST_HEAD_INITIALIZER(ready_list); int ret = 0; bool progress; + bool use_notify_me; int64_t timeout; int64_t start = 0; @@ -566,33 +561,39 @@ bool aio_poll(AioContext *ctx, bool blocking) */ assert(in_aio_context_home_thread(ctx)); - /* aio_notify can avoid the expensive event_notifier_set if + qemu_lockcnt_inc(&ctx->list_lock); + + if (ctx->poll_max_ns) { + start = qemu_clock_get_ns(QEMU_CLOCK_REALTIME); + } + + timeout = blocking ? aio_compute_timeout(ctx) : 0; + progress = try_poll_mode(ctx, &timeout); + assert(!(timeout && progress)); + + /* + * aio_notify can avoid the expensive event_notifier_set if * everything (file descriptors, bottom halves, timers) will * be re-evaluated before the next blocking poll(). This is * already true when aio_poll is called with blocking == false; * if blocking == true, it is only true after poll() returns, * so disable the optimization now. */ - if (blocking) { + use_notify_me = timeout != 0; + if (use_notify_me) { atomic_set(&ctx->notify_me, atomic_read(&ctx->notify_me) + 2); /* - * Write ctx->notify_me before computing the timeout - * (reading bottom half flags, etc.). Pairs with + * Write ctx->notify_me before reading ctx->notified. Pairs with * smp_mb in aio_notify(). */ smp_mb(); - } - - qemu_lockcnt_inc(&ctx->list_lock); - if (ctx->poll_max_ns) { - start = qemu_clock_get_ns(QEMU_CLOCK_REALTIME); + /* Don't block if aio_notify() was called */ + if (atomic_read(&ctx->notified)) { + timeout = 0; + } } - timeout = blocking ? aio_compute_timeout(ctx) : 0; - progress = try_poll_mode(ctx, &timeout); - assert(!(timeout && progress)); - /* If polling is allowed, non-blocking aio_poll does not need the * system call---a single round of run_poll_handlers_once suffices. */ @@ -600,12 +601,14 @@ bool aio_poll(AioContext *ctx, bool blocking) ret = ctx->fdmon_ops->wait(ctx, &ready_list, timeout); } - if (blocking) { + if (use_notify_me) { /* Finish the poll before clearing the flag. */ - atomic_store_release(&ctx->notify_me, atomic_read(&ctx->notify_me) - 2); - aio_notify_accept(ctx); + atomic_store_release(&ctx->notify_me, + atomic_read(&ctx->notify_me) - 2); } + aio_notify_accept(ctx); + /* Adjust polling time */ if (ctx->poll_max_ns) { int64_t block_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME) - start; diff --git a/util/async.c b/util/async.c index 1319eee..4266745 100644 --- a/util/async.c +++ b/util/async.c @@ -419,25 +419,32 @@ LuringState *aio_get_linux_io_uring(AioContext *ctx) void aio_notify(AioContext *ctx) { - /* Write e.g. bh->scheduled before reading ctx->notify_me. Pairs + /* + * Write e.g. bh->flags before writing ctx->notified. Pairs with smp_mb in + * aio_notify_accept. + */ + smp_wmb(); + atomic_set(&ctx->notified, true); + + /* + * Write ctx->notified before reading ctx->notify_me. Pairs * with smp_mb in aio_ctx_prepare or aio_poll. */ smp_mb(); if (atomic_read(&ctx->notify_me)) { event_notifier_set(&ctx->notifier); - atomic_mb_set(&ctx->notified, true); } } void aio_notify_accept(AioContext *ctx) { - if (atomic_xchg(&ctx->notified, false) -#ifdef WIN32 - || true -#endif - ) { - event_notifier_test_and_clear(&ctx->notifier); - } + atomic_set(&ctx->notified, false); + + /* + * Write ctx->notified before reading e.g. bh->flags. Pairs with smp_wmb + * in aio_notify. + */ + smp_mb(); } static void aio_timerlist_notify(void *opaque, QEMUClockType type) @@ -445,12 +452,15 @@ static void aio_timerlist_notify(void *opaque, QEMUClockType type) aio_notify(opaque); } -static void event_notifier_dummy_cb(EventNotifier *e) +static void aio_context_notifier_cb(EventNotifier *e) { + AioContext *ctx = container_of(e, AioContext, notifier); + + event_notifier_test_and_clear(&ctx->notifier); } /* Returns true if aio_notify() was called (e.g. a BH was scheduled) */ -static bool event_notifier_poll(void *opaque) +static bool aio_context_notifier_poll(void *opaque) { EventNotifier *e = opaque; AioContext *ctx = container_of(e, AioContext, notifier); @@ -508,8 +518,8 @@ AioContext *aio_context_new(Error **errp) aio_set_event_notifier(ctx, &ctx->notifier, false, - event_notifier_dummy_cb, - event_notifier_poll); + aio_context_notifier_cb, + aio_context_notifier_poll); #ifdef CONFIG_LINUX_AIO ctx->linux_aio = NULL; #endif |