Re: [PATCH] Force processes to non-realtime before mm_exit

From: Corey Minyard
Date: Sat Jun 04 2016 - 20:28:28 EST

On 06/03/2016 06:18 PM, Brian Silverman wrote:
Without this, a realtime process which has called mlockall exiting
causes large latencies for other realtime processes at the same or
lower priorities. This seems like a fairly common use case too, because
realtime processes generally want their memory locked into RAM.

Could this cause a subtle priority inversion for a process waiting
on this process to die? I'm thinking that if this is a critical process,
it crashes, and the system is very busy with other RT processes,
it could take a long time before the process gets restarted when
it is expected to happen quickly.

I don't have another solution for you, and beyond speeding up the
memory reclamation process (which may not be possible or easy)
I'm not sure there is. I'm just pointing out a possible side effect.


Signed-off-by: Brian Silverman <brian@xxxxxxxxxxxxxxxx>
kernel/exit.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/kernel/exit.c b/kernel/exit.c
index a0cf72b..68a97df 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -730,6 +730,12 @@ void do_exit(long code)
tsk->exit_code = code;
taskstats_exit(tsk, group_dead);
+ if (tsk->policy == SCHED_FIFO || tsk->policy == SCHED_RR) {
+ struct sched_param param = { .sched_priority = 0 };
+ sched_setscheduler_nocheck(current, SCHED_NORMAL, &param);
+ }
if (group_dead)