We're always _only_ waking up tasks from within the sp_threads list, so
we know that they are enqueued and alive. The rq_wait waitqueue is just
a distraction with extra atomic semantics.
Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
---
include/linux/sunrpc/svc.h | 1 -
net/sunrpc/svc.c | 2 --
net/sunrpc/svc_xprt.c | 32 +++++++++++++++++---------------
3 files changed, 17 insertions(+), 18 deletions(-)
diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index 1bc7cd05b22e..3ec769b65c7f 100644
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -280,7 +280,6 @@ struct svc_rqst {
int rq_splice_ok; /* turned off in gss privacy
* to prevent encrypting page
* cache pages */
- wait_queue_head_t rq_wait; /* synchronization */
struct task_struct *rq_task; /* service thread */
};
diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index 5de6801cd924..dfb78c4f3031 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -612,8 +612,6 @@ svc_prepare_thread(struct svc_serv *serv, struct svc_pool *pool, int node)
if (!rqstp)
goto out_enomem;
- init_waitqueue_head(&rqstp->rq_wait);
-
serv->sv_nrthreads++;
spin_lock_bh(&pool->sp_lock);
pool->sp_nrthreads++;
diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
index 2c30193c7a13..438e91c12851 100644
--- a/net/sunrpc/svc_xprt.c
+++ b/net/sunrpc/svc_xprt.c
@@ -348,8 +348,6 @@ static void svc_xprt_do_enqueue(struct svc_xprt *xprt)
cpu = get_cpu();
pool = svc_pool_for_cpu(xprt->xpt_server, cpu);
- put_cpu();
-
spin_lock_bh(&pool->sp_lock);
if (!list_empty(&pool->sp_threads) &&
@@ -382,10 +380,15 @@ static void svc_xprt_do_enqueue(struct svc_xprt *xprt)
printk(KERN_ERR
"svc_xprt_enqueue: server %p, rq_xprt=%p!\n",
rqstp, rqstp->rq_xprt);
- rqstp->rq_xprt = xprt;
+ /* Note the order of the following 3 lines:
+ * We want to assign xprt to rqstp->rq_xprt only _after_
+ * we've woken up the process, so that we don't race with
+ * the lockless check in svc_get_next_xprt().
+ */
svc_xprt_get(xprt);
+ wake_up_process(rqstp->rq_task);
+ rqstp->rq_xprt = xprt;
pool->sp_stats.threads_woken++;
- wake_up(&rqstp->rq_wait);
} else {
dprintk("svc: transport %p put into queue\n", xprt);
list_add_tail(&xprt->xpt_ready, &pool->sp_sockets);
@@ -394,6 +397,7 @@ static void svc_xprt_do_enqueue(struct svc_xprt *xprt)
out_unlock:
spin_unlock_bh(&pool->sp_lock);
+ put_cpu();
}
/*
@@ -509,7 +513,7 @@ void svc_wake_up(struct svc_serv *serv)
svc_thread_dequeue(pool, rqstp);
rqstp->rq_xprt = NULL;
*/
- wake_up(&rqstp->rq_wait);
+ wake_up_process(rqstp->rq_task);
} else
pool->sp_task_pending = 1;
spin_unlock_bh(&pool->sp_lock);
@@ -628,7 +632,6 @@ static struct svc_xprt *svc_get_next_xprt(struct svc_rqst *rqstp, long timeout)
{
struct svc_xprt *xprt;
struct svc_pool *pool = rqstp->rq_pool;
- DECLARE_WAITQUEUE(wait, current);
long time_left;
/* Normally we will wait up to 5 seconds for any required
@@ -654,15 +657,15 @@ static struct svc_xprt *svc_get_next_xprt(struct svc_rqst *rqstp, long timeout)
xprt = ERR_PTR(-EAGAIN);
goto out;
}
- /* No data pending. Go to sleep */
- svc_thread_enqueue(pool, rqstp);
-
/*
* We have to be able to interrupt this wait
* to bring down the daemons ...
*/
set_current_state(TASK_INTERRUPTIBLE);
+ /* No data pending. Go to sleep */
+ svc_thread_enqueue(pool, rqstp);
+
/*
* checking kthread_should_stop() here allows us to avoid
* locking and signalling when stopping kthreads that call
@@ -676,14 +679,13 @@ static struct svc_xprt *svc_get_next_xprt(struct svc_rqst *rqstp, long timeout)
goto out;
}
- add_wait_queue(&rqstp->rq_wait, &wait);
spin_unlock_bh(&pool->sp_lock);
time_left = schedule_timeout(timeout);
+ __set_current_state(TASK_RUNNING);
try_to_freeze();
- remove_wait_queue(&rqstp->rq_wait, &wait);
xprt = rqstp->rq_xprt;
if (xprt != NULL)
return xprt;
@@ -786,10 +788,10 @@ int svc_recv(struct svc_rqst *rqstp, long timeout)
printk(KERN_ERR
"svc_recv: service %p, transport not NULL!\n",
rqstp);
- if (waitqueue_active(&rqstp->rq_wait))
- printk(KERN_ERR
- "svc_recv: service %p, wait queue active!\n",
- rqstp);
+
+ /* Make sure the task pointer is set! */
+ if (WARN_ON_ONCE(!rqstp->rq_task))
+ rqstp->rq_task = current_task;
err = svc_alloc_arg(rqstp);
if (err)
--
1.9.3
--
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