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Subject: + kfence-maximize-allocation-wait-timeout-duration.patch added to -mm tree
Date: Tue, 20 Apr 2021 19:46:15 -0700	[thread overview]
Message-ID: <> (raw)

The patch titled
     Subject: kfence: maximize allocation wait timeout duration
has been added to the -mm tree.  Its filename is

This patch should soon appear at
and later at

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From: Marco Elver <>
Subject: kfence: maximize allocation wait timeout duration

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.  [1]

Fix it by computing the timeout duration in terms of the current
sysctl_hung_task_timeout_secs value.

Signed-off-by: Marco Elver <>
Cc: Alexander Potapenko <>
Cc: Dmitry Vyukov <>
Cc: Hillf Danton <>
Cc: Jann Horn <>
Cc: Mark Rutland <>
Signed-off-by: Andrew Morton <>

 mm/kfence/core.c |   12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

--- a/mm/kfence/core.c~kfence-maximize-allocation-wait-timeout-duration
+++ a/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>
@@ -626,7 +627,16 @@ static void toggle_allocation_gate(struc
 	WRITE_ONCE(kfence_timer_waiting, true);
 	smp_mb(); /* See comment in __kfence_alloc(). */
-	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));
+	}
 	smp_store_release(&kfence_timer_waiting, false); /* Order after wait_event(). */
 	/* Disable static key and reset timer. */

Patches currently in -mm which might be from are


             reply	other threads:[~2021-04-21  2:46 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-21  2:46 akpm [this message]
2021-04-22  4:17 + kfence-maximize-allocation-wait-timeout-duration.patch added to -mm tree akpm

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