[Qemu-block] [PATCH 39/40] async: remove unnecessary inc/dec pairs

[Paolo Bonzini]

Pull the increment/decrement pair out of aio_bh_poll and into the
callers.

Signed-off-by: Paolo Bonzini <address@hidden>
---
 aio-posix.c |  7 ++-----
 aio-win32.c |  9 ++++++---
 async.c     | 12 ++++++------
 3 files changed, 14 insertions(+), 14 deletions(-)

diff --git a/aio-posix.c b/aio-posix.c
index b372816..23dcbaa 100644
--- a/aio-posix.c
+++ b/aio-posix.c
@@ -346,9 +346,8 @@ 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);
 
@@ -461,12 +460,10 @@ bool aio_poll(AioContext *ctx, bool blocking)
     }
 
     npfd = 0;
-    qemu_lockcnt_dec(&ctx->list_lock);
 
     progress |= aio_bh_poll(ctx);
-
-    qemu_lockcnt_inc(&ctx->list_lock);
     progress |= aio_dispatch_handlers(ctx);
+
     qemu_lockcnt_dec(&ctx->list_lock);
 
     progress |= timerlistgroup_run_timers(&ctx->tlg);
diff --git a/aio-win32.c b/aio-win32.c
index feffdc4..36d39f7 100644
--- a/aio-win32.c
+++ b/aio-win32.c
@@ -231,8 +231,6 @@ static bool aio_dispatch_handlers(AioContext *ctx, HANDLE 
event)
     AioHandler *node;
     bool progress = false;
 
-    qemu_lockcnt_inc(&ctx->list_lock);
-
     /*
      * We have to walk very carefully in case aio_set_fd_handler is
      * called while we're walking.
@@ -282,14 +280,15 @@ 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);
 }
 
@@ -350,6 +349,7 @@ bool aio_poll(AioContext *ctx, bool blocking)
 
         if (first) {
             aio_notify_accept(ctx);
+            qemu_lockcnt_inc(&ctx->list_lock);
             progress |= aio_bh_poll(ctx);
             first = false;
         }
@@ -369,6 +369,9 @@ bool aio_poll(AioContext *ctx, bool blocking)
         progress |= aio_dispatch_handlers(ctx, event);
     } while (count > 0);
 
+    assert(!first); /* and lockcnt incremented */
+    qemu_lockcnt_dec(&ctx->list_lock);
+
     progress |= timerlistgroup_run_timers(&ctx->tlg);
 
     return progress;
diff --git a/async.c b/async.c
index 529934c..db05243 100644
--- a/async.c
+++ b/async.c
@@ -64,15 +64,16 @@ 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);
@@ -98,11 +99,10 @@ 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;
@@ -113,7 +113,7 @@ 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;
 }
-- 
1.8.3.1