This is a note to let you know that I've just added the patch titled
kfence: maximize allocation wait timeout duration
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-maximize-allocation-wait-timeout-duration.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 37c9284f6932b915043717703d6496dfd59c85f5 Mon Sep 17 00:00:00 2001
From: Marco Elver <elver@xxxxxxxxxx>
Date: Tue, 4 May 2021 18:40:24 -0700
Subject: kfence: maximize allocation wait timeout duration
From: Marco Elver <elver@xxxxxxxxxx>
commit 37c9284f6932b915043717703d6496dfd59c85f5 upstream.
The allocation wait timeout was initially added because of warnings due to
CONFIG_DETECT_HUNG_TASK=y [1]. While the 1 sec timeout is sufficient to
resolve the warnings (given the hung task timeout must be 1 sec or larger)
it may cause unnecessary wake-ups if the system is idle:
https://lkml.kernel.org/r/CADYN=9J0DQhizAGB0-jz4HOBBh+05kMBXb4c0cXMS7Qi5NAJiw@xxxxxxxxxxxxxx
Fix it by computing the timeout duration in terms of the current
sysctl_hung_task_timeout_secs value.
Link: https://lkml.kernel.org/r/20210421105132.3965998-3-elver@xxxxxxxxxx
Signed-off-by: Marco Elver <elver@xxxxxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Hillf Danton <hdanton@xxxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
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 | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
--- a/mm/kfence/core.c
+++ b/mm/kfence/core.c
@@ -20,6 +20,7 @@
#include <linux/moduleparam.h>
#include <linux/random.h>
#include <linux/rcupdate.h>
+#include <linux/sched/sysctl.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
@@ -620,7 +621,16 @@ static void toggle_allocation_gate(struc
/* Enable static key, and await allocation to happen. */
static_branch_enable(&kfence_allocation_key);
- wait_event_timeout(allocation_wait, atomic_read(&kfence_allocation_gate), HZ);
+ if (sysctl_hung_task_timeout_secs) {
+ /*
+ * 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);
+ } else {
+ wait_event(allocation_wait, atomic_read(&kfence_allocation_gate));
+ }
/* Disable static key and reset timer. */
static_branch_disable(&kfence_allocation_key);
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
