sched/core: Report correct state for TASK_IDLE | TASK_FREEZABLE

[ Upstream commit 0d6b35283bcf1a379cf20066544af8e6a6b16b46 ]

task_state_index() ignores uninteresting state flags (such as
TASK_FREEZABLE) for most states, but for TASK_IDLE and TASK_RTLOCK_WAIT
it does not.

So if a task is waiting TASK_IDLE|TASK_FREEZABLE it gets incorrectly
reported as TASK_UNINTERRUPTIBLE or "D".  (it is planned for nfsd to
change to use this state).

Fix this by only testing the interesting bits and not the irrelevant
bits in __task_state_index()

Signed-off-by: NeilBrown <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Stable-dep-of: f718faf3940e ("freezer, sched: Report frozen tasks as 'D' instead of 'R'")
Signed-off-by: Sasha Levin <[email protected]>

Author: neilbrown

include/linux/sched.h

@@ -1663,15 +1663,15 @@ static inline unsigned int __task_state_index(unsigned int tsk_state,
 
 	BUILD_BUG_ON_NOT_POWER_OF_2(TASK_REPORT_MAX);
 
-	if (tsk_state == TASK_IDLE)
+	if ((tsk_state & TASK_IDLE) == TASK_IDLE)
 		state = TASK_REPORT_IDLE;
 
 	/*
 	 * We're lying here, but rather than expose a completely new task state
 	 * to userspace, we can make this appear as if the task has gone through
 	 * a regular rt_mutex_lock() call.
 	 */
-	if (tsk_state == TASK_RTLOCK_WAIT)
+	if (tsk_state & TASK_RTLOCK_WAIT)
 		state = TASK_UNINTERRUPTIBLE;
 
 	return fls(state);