This is a note to let you know that I've just added the patch titled
kfence: use TASK_IDLE when awaiting allocation
to the 5.12-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kfence-use-task_idle-when-awaiting-allocation.patch
and it can be found in the queue-5.12 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 8fd0e995cc7b6a7a8a40bc03d52a2cd445beeff4 Mon Sep 17 00:00:00 2001
From: Marco Elver <elver@xxxxxxxxxx>
Date: Fri, 4 Jun 2021 20:01:11 -0700
Subject: kfence: use TASK_IDLE when awaiting allocation
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. */
Patches currently in stable-queue which might be from elver@xxxxxxxxxx are
queue-5.12/kfence-maximize-allocation-wait-timeout-duration.patch
queue-5.12/kfence-use-task_idle-when-awaiting-allocation.patch
