Messages in this thread | | | Date | Mon, 24 May 2021 12:26:17 +0100 | From | Mark Rutland <> | Subject | Re: [PATCH] irqflags: Remove the CONFIG_TRACE_IRQFLAGS |
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On Mon, May 24, 2021 at 10:51:19AM +0800, Yejune Deng wrote: > trace_hardirqs_on() and trace_hardirqs_off() had include the > CONFIG_TRACE_IRQFLAGS, so remove the redundant CONFIG_TRACE_IRQFLAGS. > > Signed-off-by: Yejune Deng <yejunedeng@gmail.com> > --- > include/linux/irqflags.h | 16 ---------------- > 1 file changed, 16 deletions(-) > > diff --git a/include/linux/irqflags.h b/include/linux/irqflags.h > index 600c10d..b5edd7b 100644 > --- a/include/linux/irqflags.h > +++ b/include/linux/irqflags.h > @@ -189,12 +189,6 @@ extern void warn_bogus_irq_restore(void); > #define raw_irqs_disabled() (arch_irqs_disabled()) > #define raw_safe_halt() arch_safe_halt() > > -/* > - * The local_irq_*() APIs are equal to the raw_local_irq*() > - * if !TRACE_IRQFLAGS. > - */ > -#ifdef CONFIG_TRACE_IRQFLAGS > - > #define local_irq_enable() \ > do { \ > trace_hardirqs_on(); \ > @@ -230,16 +224,6 @@ extern void warn_bogus_irq_restore(void); > } while (0) > > > -#else /* !CONFIG_TRACE_IRQFLAGS */ > - > -#define local_irq_enable() do { raw_local_irq_enable(); } while (0) > -#define local_irq_disable() do { raw_local_irq_disable(); } while (0)
The implementation we're left with is:
| #define local_irq_disable() \ | do { \ | bool was_disabled = raw_irqs_disabled();\ | raw_local_irq_disable(); \ | if (!was_disabled) \ | trace_hardirqs_off(); \ | } while (0)
... where the compiler almost certainly won't be able to optimize away the call to raw_irqs_disabled(), which wraps arch_irqs_disabled(). Note that arch_irqs_disabled() is typically implemented with a volatile asm block to save the processor flags.
We could special-case local_irq_disable() to prevent this, or we could leave it as-is. I'd err towards the latter.
Thanks, Mark.
> -#define local_irq_save(flags) do { raw_local_irq_save(flags); } while (0) > -#define local_irq_restore(flags) do { raw_local_irq_restore(flags); } while (0) > -#define safe_halt() do { raw_safe_halt(); } while (0) > - > -#endif /* CONFIG_TRACE_IRQFLAGS */ > - > #define local_save_flags(flags) raw_local_save_flags(flags) > > /* > -- > 2.7.4 >
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