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| author |   Eric W. Biederman <ebiederm@xmission.com> | 2019-09-14 07:34:30 -0500 |
|---|---|---|
| committer |   Ingo Molnar <mingo@kernel.org> | 2019-09-25 17:42:29 +0200 |
| commit | 154abafc68bfb7c2ef2ad5308a3b2de8968c3f61 (patch) | |
| tree | 764142945e91bb8943633d7e8eee33b6c13f7bbf /kernel/sched | |
| parent | tasks, sched/core: Ensure tasks are available for a grace period after leaving the runqueue (diff) | |
| download | linux-dev-154abafc68bfb7c2ef2ad5308a3b2de8968c3f61.tar.xz linux-dev-154abafc68bfb7c2ef2ad5308a3b2de8968c3f61.zip | |
tasks, sched/core: With a grace period after finish_task_switch(), remove unnecessary code
Remove work arounds that were written before there was a grace period
after tasks left the runqueue in finish_task_switch().
In particular now that there tasks exiting the runqueue exprience
a RCU grace period none of the work performed by task_rcu_dereference()
excpet the rcu_dereference() is necessary so replace task_rcu_dereference()
with rcu_dereference().
Remove the code in rcuwait_wait_event() that checks to ensure the current
task has not exited. It is no longer necessary as it is guaranteed
that any running task will experience a RCU grace period after it
leaves the run queueue.
Remove the comment in rcuwait_wake_up() as it is no longer relevant.
Ref: 8f95c90ceb54 ("sched/wait, RCU: Introduce rcuwait machinery")
Ref: 150593bf8693 ("sched/api: Introduce task_rcu_dereference() and try_get_task_struct()")
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Kirill Tkhai <tkhai@yandex.ru>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Russell King - ARM Linux admin <linux@armlinux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/87lfurdpk9.fsf_-_@x220.int.ebiederm.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/sched')
| -rw-r--r-- | kernel/sched/fair.c | 2 | ||||
| -rw-r--r-- | kernel/sched/membarrier.c | 4 |
2 files changed, 3 insertions, 3 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 3101c662426d..5bc23996ffae 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1602,7 +1602,7 @@ static void task_numa_compare(struct task_numa_env *env, return; rcu_read_lock(); - cur = task_rcu_dereference(&dst_rq->curr); + cur = rcu_dereference(dst_rq->curr); if (cur && ((cur->flags & PF_EXITING) || is_idle_task(cur))) cur = NULL; diff --git a/kernel/sched/membarrier.c b/kernel/sched/membarrier.c index aa8d75804108..b14250a11608 100644 --- a/kernel/sched/membarrier.c +++ b/kernel/sched/membarrier.c @@ -71,7 +71,7 @@ static int membarrier_global_expedited(void) continue; rcu_read_lock(); - p = task_rcu_dereference(&cpu_rq(cpu)->curr); + p = rcu_dereference(cpu_rq(cpu)->curr); if (p && p->mm && (atomic_read(&p->mm->membarrier_state) & MEMBARRIER_STATE_GLOBAL_EXPEDITED)) { if (!fallback) @@ -150,7 +150,7 @@ static int membarrier_private_expedited(int flags) if (cpu == raw_smp_processor_id()) continue; rcu_read_lock(); - p = task_rcu_dereference(&cpu_rq(cpu)->curr); + p = rcu_dereference(cpu_rq(cpu)->curr); if (p && p->mm == current->mm) { if (!fallback) __cpumask_set_cpu(cpu, tmpmask); |