diff options
| author | Oleg Nesterov <oleg@redhat.com> | 2010-05-19 14:57:11 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2010-06-09 10:34:50 +0200 |
| commit | 246d86b51845063e4b06b27579990492dc5fa317 (patch) | |
| tree | 3f60fc00b8cc587826cc76e31a1afb92353d08dd /kernel/sched.c | |
| parent | c676329abb2b8359d9a5d734dec0c81779823fd6 (diff) | |
sched: Simplify the reacquire_kernel_lock() logic
- Contrary to what 6d558c3a says, there is no need to reload
prev = rq->curr after the context switch. You always schedule
back to where you came from, prev must be equal to current
even if cpu/rq was changed.
- This also means reacquire_kernel_lock() can use prev instead
of current.
- No need to reassign switch_count if reacquire_kernel_lock()
reports need_resched(), we can just move the initial assignment
down, under the "need_resched_nonpreemptible:" label.
- Try to update the comment after context_switch().
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20100519125711.GA30199@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/sched.c')
| -rw-r--r-- | kernel/sched.c | 13 |
1 files changed, 6 insertions, 7 deletions
diff --git a/kernel/sched.c b/kernel/sched.c index 3abd8f780da..f37a9618fac 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -3636,7 +3636,6 @@ need_resched: rq = cpu_rq(cpu); rcu_note_context_switch(cpu); prev = rq->curr; - switch_count = &prev->nivcsw; release_kernel_lock(prev); need_resched_nonpreemptible: @@ -3649,6 +3648,7 @@ need_resched_nonpreemptible: raw_spin_lock_irq(&rq->lock); clear_tsk_need_resched(prev); + switch_count = &prev->nivcsw; if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) { if (unlikely(signal_pending_state(prev->state, prev))) { prev->state = TASK_RUNNING; @@ -3689,8 +3689,10 @@ need_resched_nonpreemptible: context_switch(rq, prev, next); /* unlocks the rq */ /* - * the context switch might have flipped the stack from under - * us, hence refresh the local variables. + * The context switch have flipped the stack from under us + * and restored the local variables which were saved when + * this task called schedule() in the past. prev == current + * is still correct, but it can be moved to another cpu/rq. */ cpu = smp_processor_id(); rq = cpu_rq(cpu); @@ -3699,11 +3701,8 @@ need_resched_nonpreemptible: post_schedule(rq); - if (unlikely(reacquire_kernel_lock(current) < 0)) { - prev = rq->curr; - switch_count = &prev->nivcsw; + if (unlikely(reacquire_kernel_lock(prev))) goto need_resched_nonpreemptible; - } preempt_enable_no_resched(); if (need_resched()) |