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sched: Fix TASK_state comparisons

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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: f5d39b0208 ("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>
This commit is contained in:
Peter Zijlstra 2022-09-27 21:02:34 +02:00
parent 7e9518baed
commit 5aec788aeb
3 changed files with 8 additions and 4 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

2
include/linux/wait.h
View file

@ -281,7 +281,7 @@ static inline void wake_up_pollfree(struct wait_queue_head *wq_head)
#define ___wait_is_interruptible(state) \ #define ___wait_is_interruptible(state) \
(!__builtin_constant_p(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); extern void init_wait_entry(struct wait_queue_entry *wq_entry, int flags);

8
kernel/hung_task.c
View file

@ -191,6 +191,8 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout)
hung_task_show_lock = false; hung_task_show_lock = false;
rcu_read_lock(); rcu_read_lock();
for_each_process_thread(g, t) { for_each_process_thread(g, t) {
unsigned int state;
if (!max_count--) if (!max_count--)
goto unlock; goto unlock;
if (time_after(jiffies, last_break + HUNG_TASK_LOCK_BREAK)) { 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; goto unlock;
last_break = jiffies; last_break = jiffies;
} }
/* use "==" to skip the TASK_KILLABLE tasks waiting on NFS */ /* skip the TASK_KILLABLE tasks -- these can be killed */
if (READ_ONCE(t->__state) == TASK_UNINTERRUPTIBLE) state = READ_ONCE(t->__state);
if ((state & TASK_UNINTERRUPTIBLE) &&
!(state & TASK_WAKEKILL))
check_hung_task(t, timeout); check_hung_task(t, timeout);
} }
unlock: unlock:

2
kernel/sched/core.c
View file

@ -8884,7 +8884,7 @@ state_filter_match(unsigned long state_filter, struct task_struct *p)
* When looking for TASK_UNINTERRUPTIBLE skip TASK_IDLE (allows * When looking for TASK_UNINTERRUPTIBLE skip TASK_IDLE (allows
* TASK_KILLABLE). * TASK_KILLABLE).
*/ */
if (state_filter == TASK_UNINTERRUPTIBLE && state == TASK_IDLE) if (state_filter == TASK_UNINTERRUPTIBLE && (state & TASK_NOLOAD))
return false; return false;
return true; return true;