| From 31e279a0d29875b76451f8a598ec5fa54dd2ab79 Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <sashal@kernel.org> |
| Date: Thu, 20 Jan 2022 16:25:20 +0000 |
| Subject: sched/tracing: Report TASK_RTLOCK_WAIT tasks as TASK_UNINTERRUPTIBLE |
| MIME-Version: 1.0 |
| Content-Type: text/plain; charset=UTF-8 |
| Content-Transfer-Encoding: 8bit |
| |
| 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-Kรถnig <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); |
| } |
| |
| -- |
| 2.34.1 |
| |
