s390/cio: add cond_resched() in the slow_eval_known_fn() loop

[ Upstream commit 0b8eb2ee9da1e8c9b8082f404f3948aa82a057b2 ]

The scanning through subchannels during the time of an event could
take significant amount of time in case of platforms with lots of
known subchannels. This might result in higher scheduling latencies
for other tasks especially on systems with a single CPU. Add
cond_resched() call, as the loop in slow_eval_known_fn() can be
executed for a longer duration.

Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Vineeth Vijayan <vneethv@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/s390/cio/css.c b/drivers/s390/cio/css.c
index 8ecc956ecb59c16682139721acb0ea5de9c56a04..370a3a2c6de734521465a95ad50d0fb3c7a68512 100644 (file)
--- a/drivers/s390/cio/css.c
+++ b/drivers/s390/cio/css.c
@@ -529,6 +529,11 @@ static int slow_eval_known_fn(struct subchannel *sch, void *data)
                rc = css_evaluate_known_subchannel(sch, 1);
                if (rc == -EAGAIN)
                        css_schedule_eval(sch->schid);
+               /*
+                * The loop might take long time for platforms with lots of
+                * known devices. Allow scheduling here.
+                */
+               cond_resched();
        }
        return 0;
 }