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Protect server shutting down with smp barriers

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I saw a confusing hang that looked like a lack of ordering between
a waker setting shutting_down and a wait event testing it after
being woken up.  Let's see if more barriers help.

Signed-off-by: Zach Brown <zab@versity.com>
This commit is contained in:
Zach Brown
2021-03-16 13:14:45 -07:00
parent f3764b873b
commit ab5466a771
1 changed files with 18 additions and 7 deletions
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25
kmod/src/server.c
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@@ -160,10 +160,21 @@ struct commit_waiter {
int ret;
};
static bool test_shutting_down(struct server_info *server)
{
smp_rmb();
return server->shutting_down;
}
static void set_shutting_down(struct server_info *server, bool val)
{
server->shutting_down = val;
smp_rmb();
}
static void stop_server(struct server_info *server)
{
/* wait_event/wake_up provide barriers */
server->shutting_down = true;
set_shutting_down(server, true);
wake_up(&server->waitq);
}
@@ -1550,7 +1561,7 @@ static int cancel_srch_compact(struct super_block *sb, u64 rid)
*/
static void queue_farewell_work(struct server_info *server)
{
if (!server->shutting_down)
if (!test_shutting_down(server))
queue_work(server->wq, &server->farewell_work);
}
@@ -2049,7 +2060,7 @@ static void recovery_timeout(struct super_block *sb)
{
DECLARE_SERVER_INFO(sb, server);
if (!server->shutting_down)
if (!test_shutting_down(server))
queue_work(server->wq, &server->fence_pending_recov_work);
}
@@ -2114,7 +2125,7 @@ out:
static void queue_reclaim_work(struct server_info *server, unsigned long delay)
{
if (!server->shutting_down)
if (!test_shutting_down(server))
queue_delayed_work(server->wq, &server->reclaim_dwork, delay);
}
@@ -2270,7 +2281,7 @@ static void scoutfs_server_worker(struct work_struct *work)
queue_reclaim_work(server, 0);
/* wait_event/wake_up provide barriers */
wait_event_interruptible(server->waitq, server->shutting_down);
wait_event_interruptible(server->waitq, test_shutting_down(server));
shutdown:
scoutfs_info(sb, "server shutting down at "SIN_FMT, SIN_ARG(&sin));
@@ -2317,7 +2328,7 @@ int scoutfs_server_start(struct super_block *sb, u64 term)
DECLARE_SERVER_INFO(sb, server);
server->err = 0;
server->shutting_down = false;
set_shutting_down(server, false);
server->term = term;
init_completion(&server->start_comp);