On Fri, 17 Nov 2017 02:15:06 +1000
Nicholas Piggin <npig...@gmail.com> wrote:
> In local_irq_save and local_irq_restore, only call irq tracing when
> the flag state acutally changes. It is not unexpected for the state
> to go disable->disable.
>
> This allows the irq tracing code to better track superfluous
> enables and disables, and in future could issue warnings. For the
> most part they are harmless, but they can indicate that the caller
> has lost track of its irq state.
I missed this before (that was a busy time, I missed a lot of emails
then :-/ ).
Anyway, this makes sense.
Peter?
-- Steve
>
> Cc: Steven Rostedt <rost...@goodmis.org>
> Cc: Ingo Molnar <mi...@redhat.com>
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Nicholas Piggin <npig...@gmail.com>
> ---
> I wonder what you think of this patch? After a small fix to
> init/main.c and some powerpc fixes, I was able to use this patch
> and a change to warn in the lockdep code in case of redundant ops,
> to verify there were no local_irq_enable() when enabled, or
> local_irq_disable() when disabled (which was implicated in a bug).
>
> Lots of code to verify so we can't do this immediately, but I
> think it's cleaner to enforce the rule?
>
> Thanks,
> Nick
>
> include/linux/irqflags.h | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/irqflags.h b/include/linux/irqflags.h
> index 46cb57d5eb13..82287e1c6c52 100644
> --- a/include/linux/irqflags.h
> +++ b/include/linux/irqflags.h
> @@ -110,7 +110,8 @@ do { \
> #define local_irq_save(flags) \
> do { \
> raw_local_irq_save(flags); \
> - trace_hardirqs_off(); \
> + if (!raw_irqs_disabled_flags(flags)) \
> + trace_hardirqs_off(); \
> } while (0)
>
>
> @@ -118,9 +119,11 @@ do { \
> do { \
> if (raw_irqs_disabled_flags(flags)) { \
> raw_local_irq_restore(flags); \
> - trace_hardirqs_off(); \
> + if (!irqs_disabled()) \
> + trace_hardirqs_off(); \
> } else { \
> - trace_hardirqs_on(); \
> + if (irqs_disabled()) \
> + trace_hardirqs_on(); \
> raw_local_irq_restore(flags); \
> } \
> } while (0)
