From: Valentin Schneider valentin.schneider@arm.com
[ Upstream commit 25795ef6299f07ce3838f3253a9cb34f64efcfae ]
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 --- include/linux/sched.h | 8 ++++++++ 1 file changed, 8 insertions(+)
diff --git a/include/linux/sched.h b/include/linux/sched.h index 084de9b70a77..46ef8c75802f 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1622,6 +1622,14 @@ static inline unsigned int __task_state_index(unsigned int tsk_state, if (tsk_state == 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) + state = TASK_UNINTERRUPTIBLE; + return fls(state); }