kernel/hung_task.c: break RCU locks based on jiffies
check_hung_uninterruptible_tasks() is currently calling rcu_lock_break()
for every 1024 threads. But check_hung_task() is very slow if printk()
was called, and is very fast otherwise.
If many threads within some 1024 threads called printk(), the RCU grace
period might be extended enough to trigger RCU stall warnings.
Therefore, calling rcu_lock_break() for every some fixed jiffies will be
safer.
Link: http://lkml.kernel.org/r/1544800658-11423-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Acked-by: Paul E. McKenney <paulmck@linux.ibm.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/hung_task.c b/kernel/hung_task.c
index 85af0cd..4a91916 100644
--- a/kernel/hung_task.c
+++ b/kernel/hung_task.c
@@ -34,7 +34,7 @@
* is disabled during the critical section. It also controls the size of
* the RCU grace period. So it needs to be upper-bound.
*/
-#define HUNG_TASK_BATCHING 1024
+#define HUNG_TASK_LOCK_BREAK (HZ / 10)
/*
* Zero means infinite timeout - no checking done:
@@ -171,7 +171,7 @@
static void check_hung_uninterruptible_tasks(unsigned long timeout)
{
int max_count = sysctl_hung_task_check_count;
- int batch_count = HUNG_TASK_BATCHING;
+ unsigned long last_break = jiffies;
struct task_struct *g, *t;
/*
@@ -186,10 +186,10 @@
for_each_process_thread(g, t) {
if (!max_count--)
goto unlock;
- if (!--batch_count) {
- batch_count = HUNG_TASK_BATCHING;
+ if (time_after(jiffies, last_break + HUNG_TASK_LOCK_BREAK)) {
if (!rcu_lock_break(g, t))
goto unlock;
+ last_break = jiffies;
}
/* use "==" to skip the TASK_KILLABLE tasks waiting on NFS */
if (t->state == TASK_UNINTERRUPTIBLE)
