Re: [PATCH RT 6/8] sched: migrate_enable: Set state to TASK_RUNNING
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: 2019-09-17 15:31:18
Also in:
lkml
On 2019-07-27 00:56:36 [-0500], Scott Wood wrote:
quoted hunk ↗ jump to hunk
If migrate_enable() is called while a task is preparing to sleep (state != TASK_RUNNING), that triggers a debug check in stop_one_cpu(). Explicitly reset state to acknowledge that we're accepting the spurious wakeup. Signed-off-by: Scott Wood <redacted> --- kernel/sched/core.c | 8 ++++++++ 1 file changed, 8 insertions(+)diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 38a9a9df5638..eb27a9bf70d7 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c@@ -7396,6 +7396,14 @@ void migrate_enable(void) unpin_current_cpu(); preempt_lazy_enable(); preempt_enable(); + + /* + * Avoid sleeping with an existing non-running + * state. This will result in a spurious wakeup + * for the calling context. + */ + __set_current_state(TASK_RUNNING);
Do you have an example for this? I'm not too sure if we are not using a
state by doing this. Actually we were losing it and get yelled at. We do:
|rt_spin_unlock()
|{
| rt_spin_lock_fastunlock();
| migrate_enable();
|}
So save the state as part of the locking process and lose it as part of
migrate_enable() if the CPU mask was changed. I *think* we need to
preserve that state until after the migration to the other CPU.
sleeping_lock_inc(); stop_one_cpu(task_cpu(p), migration_cpu_stop, &arg); sleeping_lock_dec();
Sebastian