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| author | Valentin Schneider <valentin.schneider@arm.com> | 2021-08-11 23:13:52 +0300 |
|---|---|---|
| committer | Minda Chen <minda.chen@starfivetech.com> | 2023-11-06 14:24:37 +0300 |
| commit | 1cf350e52a4e7220b9ab5e09f546b9ce05295bea (patch) | |
| tree | 231fa059290cbe75668af17b57b470b8ef710334 | |
| parent | 47a0858334bfa170d06e04bff807d8c6a41230aa (diff) | |
| download | linux-1cf350e52a4e7220b9ab5e09f546b9ce05295bea.tar.xz | |
sched: Introduce migratable()
Some areas use preempt_disable() + preempt_enable() to safely access
per-CPU data. The PREEMPT_RT folks have shown this can also be done by
keeping preemption enabled and instead disabling migration (and acquiring a
sleepable lock, if relevant).
Introduce a helper which checks whether the current task can be migrated
elsewhere, IOW if it is pinned to its local CPU in the current
context. This can help determining if per-CPU properties can be safely
accessed.
Note that CPU affinity is not checked here, as a preemptible task can have
its affinity changed at any given time (including if it has
PF_NO_SETAFFINITY, when hotplug gets involved).
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
[bigeasy: Return false on UP, call it is_migratable().]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/20210811201354.1976839-3-valentin.schneider@arm.com
| -rw-r--r-- | include/linux/sched.h | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h index c1a927ddec64..33789b6abdc3 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1730,6 +1730,16 @@ static __always_inline bool is_percpu_thread(void) #endif } +/* Is the current task guaranteed to stay on its current CPU? */ +static inline bool is_migratable(void) +{ +#ifdef CONFIG_SMP + return preemptible() && !current->migration_disabled; +#else + return false; +#endif +} + /* Per-process atomic flags. */ #define PFA_NO_NEW_PRIVS 0 /* May not gain new privileges. */ #define PFA_SPREAD_PAGE 1 /* Spread page cache over cpuset */ |