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 df09ed53ab45909a0ba3aebcc3c245325bcf38f3..825a8f2703b4fc98e6e8e8590e116f1c24b86e4e 100644 (file)
--- a/drivers/s390/cio/css.c
+++ b/drivers/s390/cio/css.c
@@ -615,6 +615,11 @@ 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;
 }