On 2021/4/21 18:51, Marco Elver wrote:
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] 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.
Signed-off-by: Marco Elver <elver@xxxxxxxxxx>
---
mm/kfence/core.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/mm/kfence/core.c b/mm/kfence/core.c
index 235d726f88bc..9742649f3f88 100644
--- 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>
@@ -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);
