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sched/tracing: Report TASK_RTLOCK_WAIT tasks as TASK_UNINTERRUPTIBLE
[ Upstream commit 25795ef629
]
TASK_RTLOCK_WAIT currently isn't part of TASK_REPORT, thus a task blocking
on an rtlock will appear as having a task state == 0, IOW TASK_RUNNING.
The actual state is saved in p->saved_state, but reading it after reading
p->__state has a few issues:
o that could still be TASK_RUNNING in the case of e.g. rt_spin_lock
o ttwu_state_match() might have changed that to TASK_RUNNING
As pointed out by Eric, adding TASK_RTLOCK_WAIT to TASK_REPORT implies
exposing a new state to userspace tools which way not know what to do with
them. The only information that needs to be conveyed here is that a task is
waiting on an rt_mutex, which matches TASK_UNINTERRUPTIBLE - there's no
need for a new state.
Reported-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Link: https://lore.kernel.org/r/20220120162520.570782-3-valentin.schneider@arm.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
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@ -1630,6 +1630,14 @@ static inline unsigned int task_state_index(struct task_struct *tsk)
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if (tsk_state == TASK_IDLE)
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state = TASK_REPORT_IDLE;
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/*
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* We're lying here, but rather than expose a completely new task state
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* to userspace, we can make this appear as if the task has gone through
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* a regular rt_mutex_lock() call.
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*/
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if (tsk_state == TASK_RTLOCK_WAIT)
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state = TASK_UNINTERRUPTIBLE;
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return fls(state);
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}
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