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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 /lib
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 'lib')
-rw-r--r--lib/smp_processor_id.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/lib/smp_processor_id.c b/lib/smp_processor_id.c
index 157d9e31f6c2..60ba93fc42ce 100644
--- a/lib/smp_processor_id.c
+++ b/lib/smp_processor_id.c
@@ -23,7 +23,7 @@ unsigned int check_preemption_disabled(const char *what1, const char *what2)
* Kernel threads bound to a single CPU can safely use
* smp_processor_id():
*/
- if (cpumask_equal(&current->cpus_allowed, cpumask_of(this_cpu)))
+ if (cpumask_equal(current->cpus_ptr, cpumask_of(this_cpu)))
goto out;
/*