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| author |   Sebastian Andrzej Siewior <bigeasy@linutronix.de> | 2019-04-23 16:26:36 +0200 |
|---|---|---|
| committer |   Ingo Molnar <mingo@kernel.org> | 2019-06-03 11:49:37 +0200 |
| commit | 3bd3706251ee8ab67e69d9340ac2abdca217e733 (patch) | |
| tree | 4431aa630d095905d840ace6a0b86e266395f71a /kernel/fork.c | |
| parent | Linux 5.2-rc3 (diff) | |
| download | linux-dev-3bd3706251ee8ab67e69d9340ac2abdca217e733.tar.xz linux-dev-3bd3706251ee8ab67e69d9340ac2abdca217e733.zip | |
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 'kernel/fork.c')
| -rw-r--r-- | kernel/fork.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/kernel/fork.c b/kernel/fork.c index 75675b9bf6df..6be686283e55 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -894,6 +894,8 @@ static struct task_struct *dup_task_struct(struct task_struct *orig, int node) #ifdef CONFIG_STACKPROTECTOR tsk->stack_canary = get_random_canary(); #endif + if (orig->cpus_ptr == &orig->cpus_mask) + tsk->cpus_ptr = &tsk->cpus_mask; /* * One for us, one for whoever does the "release_task()" (usually |