From bd451435c02e10dd07247eae188dcca0446cc57a Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Mon, 13 Feb 2017 14:52:34 +0100 Subject: [PATCH] async: remove unnecessary inc/dec pairs Pull the increment/decrement pair out of aio_bh_poll and into the callers. Reviewed-by: Stefan Hajnoczi Signed-off-by: Paolo Bonzini Reviewed-by: Fam Zheng Reviewed-by: Daniel P. Berrange Message-id: 20170213135235.12274-18-pbonzini@redhat.com Signed-off-by: Stefan Hajnoczi --- util/aio-posix.c | 8 +++----- util/aio-win32.c | 8 ++++---- util/async.c | 12 ++++++------ 3 files changed, 13 insertions(+), 15 deletions(-) diff --git a/util/aio-posix.c b/util/aio-posix.c index 2173378570..2d51239ec6 100644 --- a/util/aio-posix.c +++ b/util/aio-posix.c @@ -425,9 +425,8 @@ static bool aio_dispatch_handlers(AioContext *ctx) void aio_dispatch(AioContext *ctx) { - aio_bh_poll(ctx); - qemu_lockcnt_inc(&ctx->list_lock); + aio_bh_poll(ctx); aio_dispatch_handlers(ctx); qemu_lockcnt_dec(&ctx->list_lock); @@ -679,16 +678,15 @@ bool aio_poll(AioContext *ctx, bool blocking) } npfd = 0; - qemu_lockcnt_dec(&ctx->list_lock); progress |= aio_bh_poll(ctx); if (ret > 0) { - qemu_lockcnt_inc(&ctx->list_lock); progress |= aio_dispatch_handlers(ctx); - qemu_lockcnt_dec(&ctx->list_lock); } + qemu_lockcnt_dec(&ctx->list_lock); + progress |= timerlistgroup_run_timers(&ctx->tlg); return progress; diff --git a/util/aio-win32.c b/util/aio-win32.c index 442a1792b7..bca496a47a 100644 --- a/util/aio-win32.c +++ b/util/aio-win32.c @@ -253,8 +253,6 @@ static bool aio_dispatch_handlers(AioContext *ctx, HANDLE event) bool progress = false; AioHandler *tmp; - qemu_lockcnt_inc(&ctx->list_lock); - /* * We have to walk very carefully in case aio_set_fd_handler is * called while we're walking. @@ -305,14 +303,15 @@ static bool aio_dispatch_handlers(AioContext *ctx, HANDLE event) } } - qemu_lockcnt_dec(&ctx->list_lock); return progress; } void aio_dispatch(AioContext *ctx) { + qemu_lockcnt_inc(&ctx->list_lock); aio_bh_poll(ctx); aio_dispatch_handlers(ctx, INVALID_HANDLE_VALUE); + qemu_lockcnt_dec(&ctx->list_lock); timerlistgroup_run_timers(&ctx->tlg); } @@ -349,7 +348,6 @@ bool aio_poll(AioContext *ctx, bool blocking) } } - qemu_lockcnt_dec(&ctx->list_lock); first = true; /* ctx->notifier is always registered. */ @@ -392,6 +390,8 @@ bool aio_poll(AioContext *ctx, bool blocking) progress |= aio_dispatch_handlers(ctx, event); } while (count > 0); + qemu_lockcnt_dec(&ctx->list_lock); + progress |= timerlistgroup_run_timers(&ctx->tlg); return progress; } diff --git a/util/async.c b/util/async.c index 187bc5bc4b..7d469eb857 100644 --- a/util/async.c +++ b/util/async.c @@ -90,15 +90,16 @@ void aio_bh_call(QEMUBH *bh) bh->cb(bh->opaque); } -/* Multiple occurrences of aio_bh_poll cannot be called concurrently */ +/* Multiple occurrences of aio_bh_poll cannot be called concurrently. + * The count in ctx->list_lock is incremented before the call, and is + * not affected by the call. + */ int aio_bh_poll(AioContext *ctx) { QEMUBH *bh, **bhp, *next; int ret; bool deleted = false; - qemu_lockcnt_inc(&ctx->list_lock); - ret = 0; for (bh = atomic_rcu_read(&ctx->first_bh); bh; bh = next) { next = atomic_rcu_read(&bh->next); @@ -123,11 +124,10 @@ int aio_bh_poll(AioContext *ctx) /* remove deleted bhs */ if (!deleted) { - qemu_lockcnt_dec(&ctx->list_lock); return ret; } - if (qemu_lockcnt_dec_and_lock(&ctx->list_lock)) { + if (qemu_lockcnt_dec_if_lock(&ctx->list_lock)) { bhp = &ctx->first_bh; while (*bhp) { bh = *bhp; @@ -138,7 +138,7 @@ int aio_bh_poll(AioContext *ctx) bhp = &bh->next; } } - qemu_lockcnt_unlock(&ctx->list_lock); + qemu_lockcnt_inc_and_unlock(&ctx->list_lock); } return ret; }