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| author | Dietmar Eggemann <dietmar.eggemann@arm.com> | 2015-02-04 14:50:24 +0900 |
|---|---|---|
| committer | Seung-Woo Kim <sw0312.kim@samsung.com> | 2016-12-14 13:41:57 +0900 |
| commit | f2ea79fb72c1a0b7ccdb09eb05715e2befa4eeba (patch) | |
| tree | 4cace6f7f9d5c592ac1e121a19914c3b29455729 /kernel | |
| parent | ee3cd3fbd1c45961722c64f7da8963c86ad8bd11 (diff) | |
HMP: Fix rt task allowed cpu mask restriction code on 1x1 system
There is an error scenario where on a 1x1 HMP system (weight of the
hmp_slow_cpu_mask is 1) the short-cut of restricting the
allowed cpu mask
of an rt tasks leads to triggering a kernel bug in the rt sched class
set_cpus_allowed function set_cpus_allowed_rt().
In case the task is on the run-queue and the weight of the required cpu mask
is 1 and this is different to the p->nr_cpus_allowed value, this back-end
function interprets this in such a way that a task changed from being
migratable to not migratable anymore and decrements the rt_nr_migratory
counter. There is a BUG_ON(!rq->rt.rt_nr_migratory) check in this code
path which triggers in this situation.
To circumvent this issue, set the number of allowed cpus for a task p to
the weight of the hmp_slow_cpu_mask before calling do_set_cpus_allowed()
in __setscheduler(). It will be set to this value in
do_set_cpus_allowed()
after the call to the sched class related backend function any way. By
doing this, set_cpus_allowed_rt() returns without trying to update the
rt_nr_migratory counter.
This patch has been tested with a test device driver requiring a
threaded
irq handler on a TC2 system with a reduced cpu mask (1 Cortex A15, 1
Cortex A7).
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Jon Medhurst <tixy@linaro.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/sched/core.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 7a00317cbd56..134c531429be 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3366,8 +3366,11 @@ static void __setscheduler(struct rq *rq, struct task_struct *p, if (cpumask_equal(&p->cpus_allowed, cpu_all_mask)) do_set_cpus_allowed(p, &hmp_slow_cpu_mask); if (!cpumask_empty(&hmp_slow_cpu_mask)) - if (cpumask_equal(&p->cpus_allowed, cpu_all_mask)) + if (cpumask_equal(&p->cpus_allowed, cpu_all_mask)) { + p->nr_cpus_allowed = + cpumask_weight(&hmp_slow_cpu_mask); do_set_cpus_allowed(p, &hmp_slow_cpu_mask); + } #endif } else p->sched_class = &fair_sched_class; |