From 5aec788aeb8eb74282b75ac1b317beb0fbb69a42 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Tue, 27 Sep 2022 21:02:34 +0200 Subject: 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 Debugged-by: Christian Borntraeger Signed-off-by: Peter Zijlstra (Intel) Tested-by: Christian Borntraeger --- kernel/hung_task.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) (limited to 'kernel/hung_task.c') diff --git a/kernel/hung_task.c b/kernel/hung_task.c index f1321c03c32a..3a15169ba2f8 100644 --- 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: -- cgit v1.2.3-59-g8ed1b