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sched/fair: Fix wrong cpu selecting from isolated domain

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We've met problems that occasionally tasks with full cpumask
(e.g. by putting it into a cpuset or setting to full affinity)
were migrated to our isolated cpus in production environment.

After some analysis, we found that it is due to the current
select_idle_smt() not considering the sched_domain mask.

Steps to reproduce on my 31-CPU hyperthreads machine:
1. with boot parameter: "isolcpus=domain,2-31"
   (thread lists: 0,16 and 1,17)
2. cgcreate -g cpu:test; cgexec -g cpu:test "test_threads"
3. some threads will be migrated to the isolated cpu16~17.

Fix it by checking the valid domain mask in select_idle_smt().

Fixes: 10e2f1acd0 ("sched/core: Rewrite and improve select_idle_siblings())
Reported-by: Wetp Zhang <wetp.zy@linux.alibaba.com>
Signed-off-by: Xunlei Pang <xlpang@linux.alibaba.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Jiang Biao <benbjiang@tencent.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/1600930127-76857-1-git-send-email-xlpang@linux.alibaba.com
This commit is contained in:
Xunlei Pang 2020-09-24 14:48:47 +08:00 • committed by Peter Zijlstra
parent 51bd5121c4
commit df3cb4ea1f
1 changed files with 5 additions and 4 deletions
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9
kernel/sched/fair.c
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@ -6080,7 +6080,7 @@ static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int
/* /*
* Scan the local SMT mask for idle CPUs. * Scan the local SMT mask for idle CPUs.
*/ */
static int select_idle_smt(struct task_struct *p, int target) static int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
{ {
int cpu; int cpu;
@ -6088,7 +6088,8 @@ static int select_idle_smt(struct task_struct *p, int target)
return -1; return -1;
for_each_cpu(cpu, cpu_smt_mask(target)) { for_each_cpu(cpu, cpu_smt_mask(target)) {
if (!cpumask_test_cpu(cpu, p->cpus_ptr)) if (!cpumask_test_cpu(cpu, p->cpus_ptr) ||
!cpumask_test_cpu(cpu, sched_domain_span(sd)))
continue; continue;
if (available_idle_cpu(cpu) || sched_idle_cpu(cpu)) if (available_idle_cpu(cpu) || sched_idle_cpu(cpu))
return cpu; return cpu;
@ -6104,7 +6105,7 @@ static inline int select_idle_core(struct task_struct *p, struct sched_domain *s
return -1; return -1;
} }
static inline int select_idle_smt(struct task_struct *p, int target) static inline int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
{ {
return -1; return -1;
} }
@ -6279,7 +6280,7 @@ symmetric:
if ((unsigned)i < nr_cpumask_bits) if ((unsigned)i < nr_cpumask_bits)
return i; return i;
i = select_idle_smt(p, target); i = select_idle_smt(p, sd, target);
if ((unsigned)i < nr_cpumask_bits) if ((unsigned)i < nr_cpumask_bits)
return i; return i;