[Qemu-devel] [PATCH] posix-aio-compat: Fix idle_threads counter

[Kevin Wolf <kwolf@redhat.com>]

A thread should only be counted as idle when it really is waiting for new
requests. Without this patch, sometimes too few threads are started as busy
threads are counted as idle.

Not sure if it makes a difference in practice outside some artificial
qemu-io/qemu-img tests, but I think the change makes sense in any case.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 posix-aio-compat.c |    6 ++----
 1 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/posix-aio-compat.c b/posix-aio-compat.c
index 6d4df9d..f3cc868 100644
--- a/posix-aio-compat.c
+++ b/posix-aio-compat.c
@@ -322,7 +322,9 @@ static void *aio_thread(void *unused)
 
         while (QTAILQ_EMPTY(&request_list) &&
                !(ret == ETIMEDOUT)) {
+            idle_threads++;
             ret = cond_timedwait(&cond, &lock, &ts);
+            idle_threads--;
         }
 
         if (QTAILQ_EMPTY(&request_list))
@@ -331,7 +333,6 @@ static void *aio_thread(void *unused)
         aiocb = QTAILQ_FIRST(&request_list);
         QTAILQ_REMOVE(&request_list, aiocb, node);
         aiocb->active = 1;
-        idle_threads--;
         mutex_unlock(&lock);
 
         switch (aiocb->aio_type & QEMU_AIO_TYPE_MASK) {
@@ -353,13 +354,11 @@ static void *aio_thread(void *unused)
 
         mutex_lock(&lock);
         aiocb->ret = ret;
-        idle_threads++;
         mutex_unlock(&lock);
 
         if (kill(pid, aiocb->ev_signo)) die("kill failed");
     }
 
-    idle_threads--;
     cur_threads--;
     mutex_unlock(&lock);
 
@@ -371,7 +370,6 @@ static void spawn_thread(void)
     sigset_t set, oldset;
 
     cur_threads++;
-    idle_threads++;
 
     /* block all signals */
     if (sigfillset(&set)) die("sigfillset");
-- 
1.7.2.3