xiaomi-sm8450/android_kernel_xiaomi_sm8450
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

sched: Make select_fallback_rq() cpuset friendly

Browse Source 
Introduce cpuset_cpus_allowed_fallback() helper to fix the cpuset problems
with select_fallback_rq(). It can be called from any context and can't use
any cpuset locks including task_lock(). It is called when the task doesn't
have online cpus in ->cpus_allowed but ttwu/etc must be able to find a
suitable cpu.

I am not proud of this patch. Everything which needs such a fat comment
can't be good even if correct. But I'd prefer to not change the locking
rules in the code I hardly understand, and in any case I believe this
simple change make the code much more correct compared to deadlocks we
currently have.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20100315091027.GA9155@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Oleg Nesterov
2010-03-15 10:10:27 +01:00
committed by Ingo Molnar
parent 6a1bdc1b57
commit 9084bb8246
3 changed files with 50 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
kernel/sched.c
View File

@@ -2300,9 +2300,7 @@ static int select_fallback_rq(int cpu, struct task_struct *p)
/* No more Mr. Nice Guy. */
if (unlikely(dest_cpu >= nr_cpu_ids)) {
cpumask_copy(&p->cpus_allowed, cpu_possible_mask);
dest_cpu = cpumask_any(cpu_active_mask);
dest_cpu = cpuset_cpus_allowed_fallback(p);
/*
* Don't tell them about moving exiting tasks or
* kernel threads (both mm NULL), since they never