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SUNRPC: get rid of the request wait queue

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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@primarydata.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
This commit is contained in:
Trond Myklebust 2014-08-03 13:03:10 -04:00 • committed by J. Bruce Fields
commit 983c684466
3 changed files with 17 additions and 18 deletions
Download patch file Download diff file Expand all files Collapse all files

1
include/linux/sunrpc/svc.h
View file

@ -280,7 +280,6 @@ struct svc_rqst {
bool 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 */
};

2
net/sunrpc/svc.c
View file

@ -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++;

32
net/sunrpc/svc_xprt.c
View file

@ -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)