diff options
| 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 /include/linux/sched.h | |
| 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 '')
| -rw-r--r-- | include/linux/sched.h | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h index 11837410690f..1b2590a8d038 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -651,7 +651,8 @@ struct task_struct { unsigned int policy; int nr_cpus_allowed; - cpumask_t cpus_allowed; + const cpumask_t *cpus_ptr; + cpumask_t cpus_mask; #ifdef CONFIG_PREEMPT_RCU int rcu_read_lock_nesting; @@ -1399,7 +1400,7 @@ extern struct pid *cad_pid; #define PF_SWAPWRITE 0x00800000 /* Allowed to write to swap */ #define PF_MEMSTALL 0x01000000 /* Stalled due to lack of memory */ #define PF_UMH 0x02000000 /* I'm an Usermodehelper process */ -#define PF_NO_SETAFFINITY 0x04000000 /* Userland is not allowed to meddle with cpus_allowed */ +#define PF_NO_SETAFFINITY 0x04000000 /* Userland is not allowed to meddle with cpus_mask */ #define PF_MCE_EARLY 0x08000000 /* Early kill for mce process policy */ #define PF_MEMALLOC_NOCMA 0x10000000 /* All allocation request will have _GFP_MOVABLE cleared */ #define PF_FREEZER_SKIP 0x40000000 /* Freezer should not count it as freezable */ |