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kfence: maximize allocation wait timeout duration

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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@mail.gmail.com

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@google.com
Signed-off-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Jann Horn <jannh@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Marco Elver 2021-05-04 18:40:24 -07:00 committed by Linus Torvalds
parent 407f1d8c1b
commit 37c9284f69
1 changed files with 11 additions and 1 deletions
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12
mm/kfence/core.c
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@ -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>
@ -621,7 +622,16 @@ static void toggle_allocation_gate(struct work_struct *work)
/* 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);