From: Mr NeilBrown <neilb@suse.de>
Date: Sun, 7 Jun 2020 23:24:36 +0000 (-0400)
Subject: LU-12678 socklnd: change ksnd_nthreads to atomic_t
X-Git-Tag: 2.13.55~24
X-Git-Url: https://git.whamcloud.com/gitweb?a=commitdiff_plain;h=refs%2Fchanges%2F21%2F39121%2F3;p=fs%2Flustre-release.git

LU-12678 socklnd: change ksnd_nthreads to atomic_t

This variable is treated like an atomic_t, but a global spinlock is
used to protect updates - and also unnecessarily to protect reads.

Change to atomic_t and avoid using the spinlock.

Signed-off-by: Mr NeilBrown <neilb@suse.de>
Change-Id: Id94d280875a9e115dc077253c49e97a725dc91e1
Reviewed-on: https://review.whamcloud.com/39121
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Chris Horn <chris.horn@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
---

diff --git a/lnet/klnds/socklnd/socklnd.c b/lnet/klnds/socklnd/socklnd.c
index 1389d4f..19777ae 100644
--- a/lnet/klnds/socklnd/socklnd.c
+++ b/lnet/klnds/socklnd/socklnd.c
@@ -2264,9 +2264,9 @@ ksocknal_base_shutdown(void)
 		}
 
 		wait_var_event_warning(&ksocknal_data.ksnd_nthreads,
-				       ksocknal_data.ksnd_nthreads == 0,
+				       atomic_read(&ksocknal_data.ksnd_nthreads) == 0,
 				       "waiting for %d threads to terminate\n",
-				       ksocknal_data.ksnd_nthreads);
+				       atomic_read(&ksocknal_data.ksnd_nthreads));
 
 		ksocknal_free_buffers();
 
diff --git a/lnet/klnds/socklnd/socklnd.h b/lnet/klnds/socklnd/socklnd.h
index c539d1b..c22a0eb 100644
--- a/lnet/klnds/socklnd/socklnd.h
+++ b/lnet/klnds/socklnd/socklnd.h
@@ -182,7 +182,7 @@ struct ksock_nal_data {
 	/* hash table of all my known peers */
 	DECLARE_HASHTABLE(ksnd_peers, SOCKNAL_PEER_HASH_BITS);
 
-	int			ksnd_nthreads;	/* # live threads */
+	atomic_t		ksnd_nthreads;	/* # live threads */
 	int			ksnd_shuttingdown; /* tell threads to exit */
 	/* schedulers information */
 	struct ksock_sched	**ksnd_schedulers;
diff --git a/lnet/klnds/socklnd/socklnd_cb.c b/lnet/klnds/socklnd/socklnd_cb.c
index 2cb93a7..815a8a2 100644
--- a/lnet/klnds/socklnd/socklnd_cb.c
+++ b/lnet/klnds/socklnd/socklnd_cb.c
@@ -1059,19 +1059,15 @@ ksocknal_thread_start(int (*fn)(void *arg), void *arg, char *name)
 	if (IS_ERR(task))
 		return PTR_ERR(task);
 
-	write_lock_bh(&ksocknal_data.ksnd_global_lock);
-	ksocknal_data.ksnd_nthreads++;
-	write_unlock_bh(&ksocknal_data.ksnd_global_lock);
+	atomic_inc(&ksocknal_data.ksnd_nthreads);
 	return 0;
 }
 
 void
 ksocknal_thread_fini (void)
 {
-	write_lock_bh(&ksocknal_data.ksnd_global_lock);
-	if (--ksocknal_data.ksnd_nthreads == 0)
+	if (atomic_dec_and_test(&ksocknal_data.ksnd_nthreads))
 		wake_up_var(&ksocknal_data.ksnd_nthreads);
-	write_unlock_bh(&ksocknal_data.ksnd_global_lock);
 }
 
 int