path: root/init
diff options
authorSebastian Andrzej Siewior <bigeasy@linutronix.de>2019-04-23 16:26:36 +0200
committerIngo Molnar <mingo@kernel.org>2019-06-03 11:49:37 +0200
commit3bd3706251ee8ab67e69d9340ac2abdca217e733 (patch)
tree4431aa630d095905d840ace6a0b86e266395f71a /init
parentf2c7c76c5d0a443053e94adb9f0918fa2fb85c3a (diff)
sched/core: Provide a pointer to the valid CPU mask
In commit: 4b53a3412d66 ("sched/core: Remove the tsk_nr_cpus_allowed() wrapper") the tsk_nr_cpus_allowed() wrapper was removed. There was not much difference in !RT but in RT we used this to implement migrate_disable(). Within a migrate_disable() section the CPU mask is restricted to single CPU while the "normal" CPU mask remains untouched. As an alternative implementation Ingo suggested to use: struct task_struct { const cpumask_t *cpus_ptr; cpumask_t cpus_mask; }; with t->cpus_ptr = &t->cpus_mask; In -RT we then can switch the cpus_ptr to: t->cpus_ptr = &cpumask_of(task_cpu(p)); in a migration disabled region. The rules are simple: - Code that 'uses' ->cpus_allowed would use the pointer. - Code that 'modifies' ->cpus_allowed would use the direct mask. Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Link: https://lkml.kernel.org/r/20190423142636.14347-1-bigeasy@linutronix.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'init')
1 files changed, 2 insertions, 1 deletions
diff --git a/init/init_task.c b/init/init_task.c
index c70ef656d0f4..3c27c0efa316 100644
--- a/init/init_task.c
+++ b/init/init_task.c
@@ -72,7 +72,8 @@ struct task_struct init_task
.static_prio = MAX_PRIO - 20,
.normal_prio = MAX_PRIO - 20,
.policy = SCHED_NORMAL,
- .cpus_allowed = CPU_MASK_ALL,
+ .cpus_ptr = &init_task.cpus_mask,
+ .cpus_mask = CPU_MASK_ALL,
.nr_cpus_allowed= NR_CPUS,
.mm = NULL,
.active_mm = &init_mm,

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