On Wed, Nov 20, 2013 at 01:07:34AM +0100, Frederic Weisbecker wrote:
> Instead of saving the hardirq state on a per CPU variable, which require
> an explicit call before the softirq handling and some complication,
> just save and restore the hardirq tracing state through functions
> return values and parameters.
>
> It simplifies a bit the black magic that works around the fact that
> softirqs can be called from hardirqs while hardirqs can nest on softirqs
> but those two cases have very different semantics and only the latter
> case assume both states.
>
> Signed-off-by: Frederic Weisbecker <fweis...@gmail.com>
> Cc: Sebastian Andrzej Siewior <bige...@linutronix.de>
> Cc: Peter Zijlstra <pet...@infradead.org>
> Cc: Ingo Molnar <mi...@kernel.org>
> Cc: Linus Torvalds <torva...@linux-foundation.org>
> Cc: Andrew Morton <a...@linux-foundation.org>
> ---
> kernel/softirq.c | 37 ++++++++++++++++---------------------
> 1 file changed, 16 insertions(+), 21 deletions(-)
>
> diff --git a/kernel/softirq.c b/kernel/softirq.c
> index eb0acf4..dc43ee8 100644
> --- a/kernel/softirq.c
> +++ b/kernel/softirq.c
> @@ -215,40 +215,35 @@ EXPORT_SYMBOL(local_bh_enable_ip);
>
> #ifdef CONFIG_TRACE_IRQFLAGS
> /*
> * When we run softirqs from irq_exit() and thus on the hardirq stack we need
> * to keep the lockdep irq context tracking as tight as possible in order to
> * not miss-qualify lock contexts and miss possible deadlocks.
> */
>
> +static inline bool lockdep_softirq_start(void)
> {
> + bool in_hardirq = false;
>
> + if (trace_hardirq_context(current)) {
> + in_hardirq = true;
> trace_hardirq_exit();
> + }
> +
> lockdep_softirq_enter();
> +
> + return in_hardirq;
> }
>
> +static inline void lockdep_softirq_end(bool in_hardirq)
> {
> lockdep_softirq_exit();
> +
> + if (in_hardirq)
> trace_hardirq_enter();
> }
Yeah, I suppose that works. Thanks!
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