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Subject[PATCH 5.12 124/161] kfence: use TASK_IDLE when awaiting allocation
Date
From: Marco Elver <elver@google.com>

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@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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
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. */

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