tick: Document TICK_ONESHOT config option

[linux-flexiantxendom0-3.2.10.git] / kernel / hung_task.c

diff --git a/kernel/hung_task.c b/kernel/hung_task.c
index d4e8417..c21449f 100644 (file)
--- a/kernel/hung_task.c
+++ b/kernel/hung_task.c
@@ -13,7 +13,7 @@
 #include <linux/freezer.h>
 #include <linux/kthread.h>
 #include <linux/lockdep.h>
-#include <linux/module.h>
+#include <linux/export.h>
 #include <linux/sysctl.h>
 
 /*
@@ -33,7 +33,7 @@ unsigned long __read_mostly sysctl_hung_task_check_count = PID_MAX_LIMIT;
 /*
  * Zero means infinite timeout - no checking done:
  */
-unsigned long __read_mostly sysctl_hung_task_timeout_secs = 120;
+unsigned long __read_mostly sysctl_hung_task_timeout_secs = CONFIG_DEFAULT_HUNG_TASK_TIMEOUT;
 
 unsigned long __read_mostly sysctl_hung_task_warnings = 10;
 
@@ -74,11 +74,17 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout)
 
        /*
         * Ensure the task is not frozen.
-        * Also, when a freshly created task is scheduled once, changes
-        * its state to TASK_UNINTERRUPTIBLE without having ever been
-        * switched out once, it musn't be checked.
+        * Also, skip vfork and any other user process that freezer should skip.
         */
-       if (unlikely(t->flags & PF_FROZEN || !switch_count))
+       if (unlikely(t->flags & (PF_FROZEN | PF_FREEZER_SKIP)))
+           return;
+
+       /*
+        * When a freshly created task is scheduled once, changes its state to
+        * TASK_UNINTERRUPTIBLE without having ever been switched out once, it
+        * musn't be checked.
+        */
+       if (unlikely(!switch_count))
                return;
 
        if (switch_count != t->last_switch_count) {
@@ -98,7 +104,7 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout)
        printk(KERN_ERR "\"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\""
                        " disables this message.\n");
        sched_show_task(t);
-       __debug_show_held_locks(t);
+       debug_show_held_locks(t);
 
        touch_nmi_watchdog();
 
@@ -111,17 +117,22 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout)
  * 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.
+ * to exit the grace period. For classic RCU, a reschedule is required.
  */
-static void rcu_lock_break(struct task_struct *g, struct task_struct *t)
+static bool rcu_lock_break(struct task_struct *g, struct task_struct *t)
 {
+       bool can_cont;
+
        get_task_struct(g);
        get_task_struct(t);
        rcu_read_unlock();
        cond_resched();
        rcu_read_lock();
+       can_cont = pid_alive(g) && pid_alive(t);
        put_task_struct(t);
        put_task_struct(g);
+
+       return can_cont;
 }
 
 /*
@@ -144,13 +155,11 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout)
 
        rcu_read_lock();
        do_each_thread(g, t) {
-               if (!--max_count)
+               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)
+                       if (!rcu_lock_break(g, t))
                                goto unlock;
                }
                /* use "==" to skip the TASK_KILLABLE tasks waiting on NFS */