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SubjectRe: [PATCH RT] sched: let softirq_count() return !0 if inside local_bh_disable()ed section
On Thu, 17 May 2018 12:22:14 +0200
Sebastian Andrzej Siewior <bigeasy@linutronix.de> wrote:

> I don't see a reason why softirq_count() shouldn't reflect the fact that
> we are within a local_bh_disable() section. I *think* it was done
> primary because in RT the softirq is slightly different (and
> preemptible) and it broke some of RCU's assumptions.
> I don't see any fallout with this change. Furthermore, all checks like
> "WARN_ON(!softirq_count())" will work and we can drop the workaround we
> currently have in the queue.

Looks to keep the paradigm closer to vanilla Linux to me.

Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

-- Steve

>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---
> include/linux/preempt.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/preempt.h b/include/linux/preempt.h
> index 0591df500e9d..d8c05a2626ca 100644
> --- a/include/linux/preempt.h
> +++ b/include/linux/preempt.h
> @@ -91,7 +91,7 @@
> # define softirq_count() (preempt_count() & SOFTIRQ_MASK)
> # define in_serving_softirq() (softirq_count() & SOFTIRQ_OFFSET)
> #else
> -# define softirq_count() (0UL)
> +# define softirq_count() (current->softirq_nestcnt)
> extern int in_serving_softirq(void);
> #endif
>

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