Re: [PATCH] sched: Fix migration_cpu_stop() return value
From: Kirill Tkhai
Date: Wed Jun 04 2014 - 07:18:55 EST
04.06.2014, 14:41, "Peter Zijlstra" <peterz@xxxxxxxxxxxxx>:
> A while ago I did a similar patch for some debugging, but looking at it
> again today I realized we should probably fix this anyway.
> Subject: sched: Fix migration_cpu_stop() return value
> There are a number of migration_cpu_stop() users; and some actually care
> about the success of the migration. So report this.
> In particular migrate_task_to() as used from task_numa_migrate()
> actually tests this return value.
> Also change set_cpus_allowed_ptr() to propagate this return value, since
> it already returns other errors.
> Cc: Lai Jiangshan <laijs@xxxxxxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> kernel/sched/core.c | 15 +++++++++++----
> 1 file changed, 11 insertions(+), 4 deletions(-)
(snipped everything because of bad email editor)
In set_cpus_allowed_ptr() p->on_rq branch can not fail.
We've changed affinity and released rq's lock, so task can migrate
on allowed cpu only (even if migration_cpu_stop fails).
And it's a little ambiguously how user should react on this EAGAIN.
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