kfence: use TASK_IDLE when awaiting allocation

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@google.com
Fixes: 407f1d8c1b5f ("kfence: await for allocation using wait_event")
Signed-off-by: Marco Elver <elver@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: David Laight <David.Laight@ACULAB.COM>
Cc: Hillf Danton <hdanton@sina.com>
Cc: <stable@vger.kernel.org>	[5.12+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/kfence/core.c b/mm/kfence/core.c
index e18fbbd..4d21ac4 100644 (file)
--- a/mm/kfence/core.c
+++ b/mm/kfence/core.c
@@ -627,10 +627,10 @@ static void toggle_allocation_gate(struct work_struct *work)
                 * 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. */