On Wed, 2012-11-14 at 21:37 +0100, Frederic Weisbecker wrote:
> Don't stop the tick if we have pending irq works on the
> queue, otherwise if the arch can't raise self-IPIs, we may not
> find an opportunity to execute the pending works for a while.
>
> Signed-off-by: Frederic Weisbecker <fweis...@gmail.com>
> Cc: Peter Zijlstra <pet...@infradead.org>
> Cc: Thomas Gleixner <t...@linutronix.de>
> Cc: Ingo Molnar <mi...@kernel.org>
> Cc: Andrew Morton <a...@linux-foundation.org>
> Cc: Steven Rostedt <rost...@goodmis.org>
> Cc: Paul Gortmaker <paul.gortma...@windriver.com>
> ---
> include/linux/irq_work.h | 6 ++++++
> kernel/irq_work.c | 11 +++++++++++
> kernel/time/tick-sched.c | 3 ++-
> 3 files changed, 19 insertions(+), 1 deletions(-)
>
> diff --git a/include/linux/irq_work.h b/include/linux/irq_work.h
> index 6a9e8f5..a69704f 100644
> --- a/include/linux/irq_work.h
> +++ b/include/linux/irq_work.h
> @@ -20,4 +20,10 @@ bool irq_work_queue(struct irq_work *work);
> void irq_work_run(void);
> void irq_work_sync(struct irq_work *work);
>
> +#ifdef CONFIG_IRQ_WORK
> +bool irq_work_needs_cpu(void);
> +#else
> +static bool irq_work_needs_cpu(void) { return false; }
> +#endif
> +
> #endif /* _LINUX_IRQ_WORK_H */
> diff --git a/kernel/irq_work.c b/kernel/irq_work.c
> index 64eddd5..b3c113a 100644
> --- a/kernel/irq_work.c
> +++ b/kernel/irq_work.c
> @@ -99,6 +99,17 @@ bool irq_work_queue(struct irq_work *work)
> }
> EXPORT_SYMBOL_GPL(irq_work_queue);
>
> +bool irq_work_needs_cpu(void)
> +{
> + struct llist_head *this_list;
> +
> + this_list = &__get_cpu_var(irq_work_list);
> + if (llist_empty(this_list))
> + return false;
> +
I wounder if this should just be:
return !llist_empty(&this_cpu_read(irq_work_list));
-- Steve
> + return true;
> +}
> +
> /*
> * Run the irq_work entries on this cpu. Requires to be ran from hardirq
> * context with local IRQs disabled.
> diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
> index 9e945aa..f249e8c 100644
> --- a/kernel/time/tick-sched.c
> +++ b/kernel/time/tick-sched.c
> @@ -20,6 +20,7 @@
> #include <linux/profile.h>
> #include <linux/sched.h>
> #include <linux/module.h>
> +#include <linux/irq_work.h>
>
> #include <asm/irq_regs.h>
>
> @@ -289,7 +290,7 @@ static ktime_t tick_nohz_stop_sched_tick(struct
> tick_sched *ts,
> } while (read_seqretry(&xtime_lock, seq));
>
> if (rcu_needs_cpu(cpu, &rcu_delta_jiffies) || printk_needs_cpu(cpu) ||
> - arch_needs_cpu(cpu)) {
> + arch_needs_cpu(cpu) || irq_work_needs_cpu()) {
> next_jiffies = last_jiffies + 1;
> delta_jiffies = 1;
> } else {
--
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