There is a race in enqueueing thread to a pool and
waking up a thread.
lockd doesn't wake up on reception of lock granted callback
if svc_wake_up() is called before lockd's thread is added
to a pool.
Signed-off-by: Andriy Skulysh <Andriy_Skulysh@xxxxxxxxxxx>
---
include/linux/sunrpc/svc.h | 1 +
net/sunrpc/svc_xprt.c | 9 ++++++++-
2 files changed, 9 insertions(+), 1 deletions(-)
diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index 676ddf5..1f0216b 100644
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -50,6 +50,7 @@ struct svc_pool {
unsigned int sp_nrthreads; /* # of threads in pool */
struct list_head sp_all_threads; /* all server threads */
struct svc_pool_stats sp_stats; /* statistics on pool operation */
+ int sp_task_pending;/* has pending task */
} ____cacheline_aligned_in_smp;
/*
diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
index b8e47fa..5a9d40c 100644
--- a/net/sunrpc/svc_xprt.c
+++ b/net/sunrpc/svc_xprt.c
@@ -499,7 +499,8 @@ void svc_wake_up(struct svc_serv *serv)
rqstp->rq_xprt = NULL;
*/
wake_up(&rqstp->rq_wait);
- }
+ } else
+ pool->sp_task_pending = 1;
spin_unlock_bh(&pool->sp_lock);
}
}
@@ -634,7 +635,13 @@ struct svc_xprt *svc_get_next_xprt(struct
svc_rqst *rqstp, long timeout)
* long for cache updates.
*/
rqstp->rq_chandle.thread_wait = 1*HZ;
+ pool->sp_task_pending = 0;
} else {
+ if (pool->sp_task_pending) {
+ pool->sp_task_pending = 0;
+ spin_unlock_bh(&pool->sp_lock);
+ return ERR_PTR(-EAGAIN);
+ }
/* No data pending. Go to sleep */
svc_thread_enqueue(pool, rqstp);
--
1.7.1
On 4 January 2013 02:53, J. Bruce Fields <bfields@xxxxxxxxxxxx> wrote:
> That should be ERR_PTR(-EAGAIN).
fixed.
>
> Other than this this looks right to me....
>
> Out of curiosity: how did you run across this problem, and how did you
> test the fix?
I can reproduce it with single ping_pong with nfs on top of Lustre filesystem.
Andriy.
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