On Wed, Apr 16, 2014 at 09:06:24AM -0700, Eric Dumazet wrote:
> From: Eric Dumazet <[email protected]>
>
> Calling rcu_bh_qs() after every softirq action is not really needed.
>
> What RCU needs is at least one rcu_bh_qs() per softirq round to note a
> quiescent state was passed for rcu_bh
>
> Note for Paul and myself : this could be inlined as a single instruction
> and avoid smp_processor_id()
> (sone this_cpu_write(rcu_bh_data.passed_quiesce, 1))
>
> Signed-off-by: Eric Dumazet <[email protected]>
Looks plausible -- will give it a go! If nothing breaks, queued for
3.16.
Thanx, Paul
> ---
> kernel/softirq.c | 4 +---
> 1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/kernel/softirq.c b/kernel/softirq.c
> index b50990a5bea0..b9b2d4906848 100644
> --- a/kernel/softirq.c
> +++ b/kernel/softirq.c
> @@ -232,7 +232,6 @@ asmlinkage void __do_softirq(void)
> bool in_hardirq;
> __u32 pending;
> int softirq_bit;
> - int cpu;
>
> /*
> * Mask out PF_MEMALLOC s current task context is borrowed for the
> @@ -247,7 +246,6 @@ asmlinkage void __do_softirq(void)
> __local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET);
> in_hardirq = lockdep_softirq_start();
>
> - cpu = smp_processor_id();
> restart:
> /* Reset the pending bitmask before enabling irqs */
> set_softirq_pending(0);
> @@ -276,11 +274,11 @@ restart:
> prev_count, preempt_count());
> preempt_count_set(prev_count);
> }
> - rcu_bh_qs(cpu);
> h++;
> pending >>= softirq_bit;
> }
>
> + rcu_bh_qs(smp_processor_id());
> local_irq_disable();
>
> pending = local_softirq_pending();
>
>
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