From 6493c975af75be5b8d9ade954239bdf5492b7911 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Tue, 21 Jul 2015 16:07:50 +0200 Subject: [PATCH] aio-win32: reorganize polling loop Preparatory bugfixes and tweaks to the loop before the next patch: - disable dispatch optimization during aio_prepare. This fixes a bug. - do not modify "blocking" until after the first WaitForMultipleObjects call. This is needed in the next patch. - change the loop to do...while. This makes it obvious that the loop is always entered at least once. In the next patch this is important because the first iteration undoes the ctx->notify_me increment that happened before entering the loop. Signed-off-by: Paolo Bonzini Reviewed-by: Fam Zheng Tested-by: Richard W.M. Jones Message-id: 1437487673-23740-4-git-send-email-pbonzini@redhat.com Signed-off-by: Stefan Hajnoczi --- aio-win32.c | 21 ++++++++++++--------- 1 file changed, 12 insertions(+), 9 deletions(-) diff --git a/aio-win32.c b/aio-win32.c index 233d8f5d79..9268b5c9fc 100644 --- a/aio-win32.c +++ b/aio-win32.c @@ -284,11 +284,6 @@ bool aio_poll(AioContext *ctx, bool blocking) int timeout; aio_context_acquire(ctx); - have_select_revents = aio_prepare(ctx); - if (have_select_revents) { - blocking = false; - } - was_dispatching = ctx->dispatching; progress = false; @@ -304,6 +299,8 @@ bool aio_poll(AioContext *ctx, bool blocking) */ aio_set_dispatching(ctx, !blocking); + have_select_revents = aio_prepare(ctx); + ctx->walking_handlers++; /* fill fd sets */ @@ -317,12 +314,18 @@ bool aio_poll(AioContext *ctx, bool blocking) ctx->walking_handlers--; first = true; - /* wait until next event */ - while (count > 0) { + /* ctx->notifier is always registered. */ + assert(count > 0); + + /* Multiple iterations, all of them non-blocking except the first, + * may be necessary to process all pending events. After the first + * WaitForMultipleObjects call ctx->notify_me will be decremented. + */ + do { HANDLE event; int ret; - timeout = blocking + timeout = blocking && !have_select_revents ? qemu_timeout_ns_to_ms(aio_compute_timeout(ctx)) : 0; if (timeout) { aio_context_release(ctx); @@ -351,7 +354,7 @@ bool aio_poll(AioContext *ctx, bool blocking) blocking = false; progress |= aio_dispatch_handlers(ctx, event); - } + } while (count > 0); progress |= timerlistgroup_run_timers(&ctx->tlg);