diff options
| -rw-r--r-- | kernel/hung_task.c | 39 |
1 files changed, 37 insertions, 2 deletions
diff --git a/kernel/hung_task.c b/kernel/hung_task.c index ba8ccd432963..481ca8b5c2bc 100644 --- a/kernel/hung_task.c +++ b/kernel/hung_task.c @@ -17,9 +17,18 @@ #include <linux/sysctl.h> /* - * Have a reasonable limit on the number of tasks checked: + * The number of tasks checked: */ -unsigned long __read_mostly sysctl_hung_task_check_count = 1024; +unsigned long __read_mostly sysctl_hung_task_check_count = PID_MAX_LIMIT; + +/* + * Limit number of tasks checked in a batch. + * + * This value controls the preemptibility of khungtaskd since preemption + * 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 /* * Zero means infinite timeout - no checking done: @@ -110,6 +119,24 @@ static void check_hung_task(struct task_struct *t, unsigned long now, } /* + * To avoid extending the RCU grace period for an unbounded amount of time, + * periodically exit the critical section and enter a new one. + * + * For preemptible RCU it is sufficient to call rcu_read_unlock in order + * exit the grace period. For classic RCU, a reschedule is required. + */ +static void rcu_lock_break(struct task_struct *g, struct task_struct *t) +{ + get_task_struct(g); + get_task_struct(t); + rcu_read_unlock(); + cond_resched(); + rcu_read_lock(); + put_task_struct(t); + put_task_struct(g); +} + +/* * Check whether a TASK_UNINTERRUPTIBLE does not get woken up for * a really long time (120 seconds). If that happens, print out * a warning. @@ -117,6 +144,7 @@ static void check_hung_task(struct task_struct *t, unsigned long now, 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 now = get_timestamp(); struct task_struct *g, *t; @@ -131,6 +159,13 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout) do_each_thread(g, t) { if (!--max_count) goto unlock; + if (!--batch_count) { + batch_count = HUNG_TASK_BATCHING; + rcu_lock_break(g, t); + /* Exit if t or g was unhashed during refresh. */ + if (t->state == TASK_DEAD || g->state == TASK_DEAD) + goto unlock; + } /* use "==" to skip the TASK_KILLABLE tasks waiting on NFS */ if (t->state == TASK_UNINTERRUPTIBLE) check_hung_task(t, now, timeout); |