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From: Stefan Hajnoczi <stefanha@redhat.com>
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Subject: [Qemu-devel] [PULL v2 17/24] async: remove unnecessary inc/dec pairs
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Cc: Peter Maydell <peter.maydell@linaro.org>,
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From: Paolo Bonzini <pbonzini@redhat.com>
Pull the increment/decrement pair out of aio_bh_poll and into the
callers.
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Daniel P. Berrange <berrange@redhat.com>
Message-id: 20170213135235.12274-18-pbonzini@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
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 2173378..2d51239 100644
--- a/util/aio-posix.c
+++ b/util/aio-posix.c
@@ -425,9 +425,8 @@ static bool aio_dispatch_handlers(AioContext *ctx)
=20
void aio_dispatch(AioContext *ctx)
{
+ qemu_lockcnt_inc(&ctx->list_lock);
aio_bh_poll(ctx);
-
- qemu_lockcnt_inc(&ctx->list_lock);
aio_dispatch_handlers(ctx);
qemu_lockcnt_dec(&ctx->list_lock);
=20
@@ -679,16 +678,15 @@ bool aio_poll(AioContext *ctx, bool blocking)
}
=20
npfd =3D 0;
- qemu_lockcnt_dec(&ctx->list_lock);
=20
progress |=3D aio_bh_poll(ctx);
=20
if (ret > 0) {
- qemu_lockcnt_inc(&ctx->list_lock);
progress |=3D aio_dispatch_handlers(ctx);
- qemu_lockcnt_dec(&ctx->list_lock);
}
=20
+ qemu_lockcnt_dec(&ctx->list_lock);
+
progress |=3D timerlistgroup_run_timers(&ctx->tlg);
=20
return progress;
diff --git a/util/aio-win32.c b/util/aio-win32.c
index 442a179..bca496a 100644
--- a/util/aio-win32.c
+++ b/util/aio-win32.c
@@ -253,8 +253,6 @@ static bool aio_dispatch_handlers(AioContext *ctx, HAND=
LE event)
bool progress =3D false;
AioHandler *tmp;
=20
- 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, HA=
NDLE event)
}
}
=20
- qemu_lockcnt_dec(&ctx->list_lock);
return progress;
}
=20
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);
}
=20
@@ -349,7 +348,6 @@ bool aio_poll(AioContext *ctx, bool blocking)
}
}
=20
- qemu_lockcnt_dec(&ctx->list_lock);
first =3D true;
=20
/* ctx->notifier is always registered. */
@@ -392,6 +390,8 @@ bool aio_poll(AioContext *ctx, bool blocking)
progress |=3D aio_dispatch_handlers(ctx, event);
} while (count > 0);
=20
+ qemu_lockcnt_dec(&ctx->list_lock);
+
progress |=3D timerlistgroup_run_timers(&ctx->tlg);
return progress;
}
diff --git a/util/async.c b/util/async.c
index 187bc5b..7d469eb 100644
--- a/util/async.c
+++ b/util/async.c
@@ -90,15 +90,16 @@ void aio_bh_call(QEMUBH *bh)
bh->cb(bh->opaque);
}
=20
-/* 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 =3D false;
=20
- qemu_lockcnt_inc(&ctx->list_lock);
-
ret =3D 0;
for (bh =3D atomic_rcu_read(&ctx->first_bh); bh; bh =3D next) {
next =3D atomic_rcu_read(&bh->next);
@@ -123,11 +124,10 @@ int aio_bh_poll(AioContext *ctx)
=20
/* remove deleted bhs */
if (!deleted) {
- qemu_lockcnt_dec(&ctx->list_lock);
return ret;
}
=20
- if (qemu_lockcnt_dec_and_lock(&ctx->list_lock)) {
+ if (qemu_lockcnt_dec_if_lock(&ctx->list_lock)) {
bhp =3D &ctx->first_bh;
while (*bhp) {
bh =3D *bhp;
@@ -138,7 +138,7 @@ int aio_bh_poll(AioContext *ctx)
bhp =3D &bh->next;
}
}
- qemu_lockcnt_unlock(&ctx->list_lock);
+ qemu_lockcnt_inc_and_unlock(&ctx->list_lock);
}
return ret;
}
--=20
2.9.3