sched: Fix TASK_state comparisons

Task state is fundamentally a bitmask; direct comparisons are probably
not working as intended. Specifically the normal wait-state have
a number of possible modifiers:

  TASK_UNINTERRUPTIBLE:	TASK_WAKEKILL, TASK_NOLOAD, TASK_FREEZABLE
  TASK_INTERRUPTIBLE:   TASK_FREEZABLE

Specifically, the addition of TASK_FREEZABLE wrecked
__wait_is_interruptible(). This however led to an audit of direct
comparisons yielding the rest of the changes.

Fixes: f5d39b020809 ("freezer,sched: Rewrite core freezer logic")
Reported-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Debugged-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Christian Borntraeger <borntraeger@linux.ibm.com>

diff --git a/include/linux/wait.h b/include/linux/wait.h
index 14ad8a0..7f5a51a 100644 (file)
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -281,7 +281,7 @@ static inline void wake_up_pollfree(struct wait_queue_head *wq_head)
 
 #define ___wait_is_interruptible(state)                                                \
        (!__builtin_constant_p(state) ||                                        \
-               state == TASK_INTERRUPTIBLE || state == TASK_KILLABLE)          \
+        (state & (TASK_INTERRUPTIBLE | TASK_WAKEKILL)))
 
 extern void init_wait_entry(struct wait_queue_entry *wq_entry, int flags);
 

diff --git a/kernel/hung_task.c b/kernel/hung_task.c
index f1321c0..3a15169 100644 (file)
--- a/kernel/hung_task.c
+++ b/kernel/hung_task.c
@@ -191,6 +191,8 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout)
        hung_task_show_lock = false;
        rcu_read_lock();
        for_each_process_thread(g, t) {
+               unsigned int state;
+
                if (!max_count--)
                        goto unlock;
                if (time_after(jiffies, last_break + HUNG_TASK_LOCK_BREAK)) {
@@ -198,8 +200,10 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout)
                                goto unlock;
                        last_break = jiffies;
                }
-               /* use "==" to skip the TASK_KILLABLE tasks waiting on NFS */
-               if (READ_ONCE(t->__state) == TASK_UNINTERRUPTIBLE)
+               /* skip the TASK_KILLABLE tasks -- these can be killed */
+               state = READ_ONCE(t->__state);
+               if ((state & TASK_UNINTERRUPTIBLE) &&
+                   !(state & TASK_WAKEKILL))
                        check_hung_task(t, timeout);
        }
  unlock:

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 4fa4a3d..02dc1b8 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -8884,7 +8884,7 @@ state_filter_match(unsigned long state_filter, struct task_struct *p)
         * When looking for TASK_UNINTERRUPTIBLE skip TASK_IDLE (allows
         * TASK_KILLABLE).
         */
-       if (state_filter == TASK_UNINTERRUPTIBLE && state == TASK_IDLE)
+       if (state_filter == TASK_UNINTERRUPTIBLE && (state & TASK_NOLOAD))
                return false;
 
        return true;