[PATCH 5.12 124/161] kfence: use TASK_IDLE when awaiting allocation

[Greg Kroah-Hartman]

From: Marco Elver <elver@xxxxxxxxxx>

commit 8fd0e995cc7b6a7a8a40bc03d52a2cd445beeff4 upstream.

Since wait_event() uses TASK_UNINTERRUPTIBLE by default, waiting for an
allocation counts towards load.  However, for KFENCE, this does not make
any sense, since there is no busy work we're awaiting.

Instead, use TASK_IDLE via wait_event_idle() to not count towards load.

BugLink: https://bugzilla.suse.com/show_bug.cgi?id=1185565
Link: https://lkml.kernel.org/r/20210521083209.3740269-1-elver@xxxxxxxxxx
Fixes: 407f1d8c1b5f ("kfence: await for allocation using wait_event")
Signed-off-by: Marco Elver <elver@xxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: David Laight <David.Laight@xxxxxxxxxx>
Cc: Hillf Danton <hdanton@xxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>	[5.12+]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 mm/kfence/core.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/mm/kfence/core.c
+++ b/mm/kfence/core.c
@@ -626,10 +626,10 @@ static void toggle_allocation_gate(struc
 		 * During low activity with no allocations we might wait a
 		 * while; let's avoid the hung task warning.
 		 */
-		wait_event_timeout(allocation_wait, atomic_read(&kfence_allocation_gate),
-				   sysctl_hung_task_timeout_secs * HZ / 2);
+		wait_event_idle_timeout(allocation_wait, atomic_read(&kfence_allocation_gate),
+					sysctl_hung_task_timeout_secs * HZ / 2);
 	} else {
-		wait_event(allocation_wait, atomic_read(&kfence_allocation_gate));
+		wait_event_idle(allocation_wait, atomic_read(&kfence_allocation_gate));
 	}
 
 	/* Disable static key and reset timer. */