diff options
| author | Andrea Parri <andrea.parri@amarulasolutions.com> | 2019-01-21 16:52:40 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2019-02-04 09:13:21 +0100 |
| commit | c546951d9c9300065bad253ecdf1ac59ce9d06c8 (patch) | |
| tree | b5f282be96ca33780d286e8bf07d1b01471aa0c9 /kernel/sched/sched.h | |
| parent | 1ca4fa3ab604734e38e2a3000c9abf788512ffa7 (diff) | |
sched/core: Use READ_ONCE()/WRITE_ONCE() in move_queued_task()/task_rq_lock()
move_queued_task() synchronizes with task_rq_lock() as follows:
move_queued_task() task_rq_lock()
[S] ->on_rq = MIGRATING [L] rq = task_rq()
WMB (__set_task_cpu()) ACQUIRE (rq->lock);
[S] ->cpu = new_cpu [L] ->on_rq
where "[L] rq = task_rq()" is ordered before "ACQUIRE (rq->lock)" by an
address dependency and, in turn, "ACQUIRE (rq->lock)" is ordered before
"[L] ->on_rq" by the ACQUIRE itself.
Use READ_ONCE() to load ->cpu in task_rq() (c.f., task_cpu()) to honor
this address dependency. Also, mark the accesses to ->cpu and ->on_rq
with READ_ONCE()/WRITE_ONCE() to comply with the LKMM.
Signed-off-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@linux.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Link: https://lkml.kernel.org/r/20190121155240.27173-1-andrea.parri@amarulasolutions.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/sched/sched.h')
| -rw-r--r-- | kernel/sched/sched.h | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 99e2a7772d16..c688ef5012e5 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1479,9 +1479,9 @@ static inline void __set_task_cpu(struct task_struct *p, unsigned int cpu) */ smp_wmb(); #ifdef CONFIG_THREAD_INFO_IN_TASK - p->cpu = cpu; + WRITE_ONCE(p->cpu, cpu); #else - task_thread_info(p)->cpu = cpu; + WRITE_ONCE(task_thread_info(p)->cpu, cpu); #endif p->wake_cpu = cpu; #endif @@ -1582,7 +1582,7 @@ static inline int task_on_rq_queued(struct task_struct *p) static inline int task_on_rq_migrating(struct task_struct *p) { - return p->on_rq == TASK_ON_RQ_MIGRATING; + return READ_ONCE(p->on_rq) == TASK_ON_RQ_MIGRATING; } /* |