linux-kernel - [PATCH 5.12 124/161] kfence: use TASK

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Date:   Tue,  8 Jun 2021 20:27:34 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Marco Elver <elver@...gle.com>,
        Mel Gorman <mgorman@...e.de>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        David Laight <David.Laight@...LAB.COM>,
        Hillf Danton <hdanton@...a.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 5.12 124/161] kfence: use TASK_IDLE when awaiting allocation

From: Marco Elver <elver@...gle.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@...gle.com>
Cc: Mel Gorman <mgorman@...e.de>
Cc: Alexander Potapenko <glider@...gle.com>
Cc: Dmitry Vyukov <dvyukov@...gle.com>
Cc: David Laight <David.Laight@...LAB.COM>
Cc: Hillf Danton <hdanton@...a.com>
Cc: <stable@...r.kernel.org>	[5.12+]
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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. */