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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/[email protected]
Signed-off-by: Marco Elver <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Cc: Hillf Danton <[email protected]>
Cc: Jann Horn <[email protected]>
Cc: Mark Rutland <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Marco Elver
2021-05-05 11:27:27 -07:00
committed by Linus Torvalds
parent 407f1d8c1b
commit 37c9284f69
1 changed files with 11 additions and 1 deletions
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mm/kfence/core.c
+11 -1
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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);