sunrpc: fix potential races in pool_stats collection

In a later patch, we'll be removing some spinlocking around the socket
and thread queueing code in order to fix some contention problems. At
that point, the stats counters will no longer be protected by the
sp_lock.

Change the counters to atomic_long_t fields, except for the
"sockets_queued" counter which will still be manipulated under a
spinlock.

Signed-off-by: Jeff Layton <jlayton@primarydata.com>
Tested-by: Chris Worley <chris.worley@primarydata.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index 7f80a99..513957e 100644 (file)
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -26,10 +26,10 @@ typedef int         (*svc_thread_fn)(void *);
 
 /* statistics for svc_pool structures */
 struct svc_pool_stats {
-       unsigned long   packets;
+       atomic_long_t   packets;
        unsigned long   sockets_queued;
-       unsigned long   threads_woken;
-       unsigned long   threads_timedout;
+       atomic_long_t   threads_woken;
+       atomic_long_t   threads_timedout;
 };
 
 /*

diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
index b2676e5..579ff22 100644 (file)
--- a/net/sunrpc/svc_xprt.c
+++ b/net/sunrpc/svc_xprt.c
@@ -362,7 +362,7 @@ static void svc_xprt_do_enqueue(struct svc_xprt *xprt)
        pool = svc_pool_for_cpu(xprt->xpt_server, cpu);
        spin_lock_bh(&pool->sp_lock);
 
-       pool->sp_stats.packets++;
+       atomic_long_inc(&pool->sp_stats.packets);
 
        if (!list_empty(&pool->sp_threads)) {
                rqstp = list_entry(pool->sp_threads.next,
@@ -383,7 +383,7 @@ static void svc_xprt_do_enqueue(struct svc_xprt *xprt)
                svc_xprt_get(xprt);
                wake_up_process(rqstp->rq_task);
                rqstp->rq_xprt = xprt;
-               pool->sp_stats.threads_woken++;
+               atomic_long_inc(&pool->sp_stats.threads_woken);
        } else {
                dprintk("svc: transport %p put into queue\n", xprt);
                list_add_tail(&xprt->xpt_ready, &pool->sp_sockets);
@@ -669,7 +669,7 @@ static struct svc_xprt *svc_get_next_xprt(struct svc_rqst *rqstp, long timeout)
 
                spin_lock_bh(&pool->sp_lock);
                if (!time_left)
-                       pool->sp_stats.threads_timedout++;
+                       atomic_long_inc(&pool->sp_stats.threads_timedout);
 
                xprt = rqstp->rq_xprt;
                if (!xprt) {
@@ -1306,10 +1306,10 @@ static int svc_pool_stats_show(struct seq_file *m, void *p)
 
        seq_printf(m, "%u %lu %lu %lu %lu\n",
                pool->sp_id,
-               pool->sp_stats.packets,
+               (unsigned long)atomic_long_read(&pool->sp_stats.packets),
                pool->sp_stats.sockets_queued,
-               pool->sp_stats.threads_woken,
-               pool->sp_stats.threads_timedout);
+               (unsigned long)atomic_long_read(&pool->sp_stats.threads_woken),
+               (unsigned long)atomic_long_read(&pool->sp_stats.threads_timedout));
 
        return 0;
 }