| Message ID | 20201113141733.864469886@linutronix.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | softirq: Cleanups and RT awareness | expand |
On Fri, Nov 13, 2020 at 03:02:17PM +0100, Thomas Gleixner wrote: > -#define irq_count() (preempt_count() & (HARDIRQ_MASK | SOFTIRQ_MASK \ > - | NMI_MASK)) > +#define irq_count() (nmi_count() | hardirq_count() | softirq_count()) > +#define in_task() (!(in_nmi() | in_hardirq() | in_serving_softirq())) > -#define in_task() (!(preempt_count() & \ > - (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET))) How horrible is the code-gen? Because preempt_count() is raw_cpu_read_4() and at least some old compilers will refuse to CSE it (consider the this_cpu_read_stable mess).
On Mon, Nov 16 2020 at 13:17, Peter Zijlstra wrote: > On Fri, Nov 13, 2020 at 03:02:17PM +0100, Thomas Gleixner wrote: > >> -#define irq_count() (preempt_count() & (HARDIRQ_MASK | SOFTIRQ_MASK \ >> - | NMI_MASK)) >> +#define irq_count() (nmi_count() | hardirq_count() | softirq_count()) > > >> +#define in_task() (!(in_nmi() | in_hardirq() | in_serving_softirq())) >> -#define in_task() (!(preempt_count() & \ >> - (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET))) > > How horrible is the code-gen? Because preempt_count() is > raw_cpu_read_4() and at least some old compilers will refuse to CSE it > (consider the this_cpu_read_stable mess). I looked at gcc8 and 10 output and the compilers are smart enough to fold it for the !RT case. But yeah ... Thanks, tglx
On Mon, Nov 16, 2020 at 06:42:19PM +0100, Thomas Gleixner wrote: > On Mon, Nov 16 2020 at 13:17, Peter Zijlstra wrote: > > On Fri, Nov 13, 2020 at 03:02:17PM +0100, Thomas Gleixner wrote: > > > >> -#define irq_count() (preempt_count() & (HARDIRQ_MASK | SOFTIRQ_MASK \ > >> - | NMI_MASK)) > >> +#define irq_count() (nmi_count() | hardirq_count() | softirq_count()) > > > > > >> +#define in_task() (!(in_nmi() | in_hardirq() | in_serving_softirq())) > >> -#define in_task() (!(preempt_count() & \ > >> - (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET))) > > > > How horrible is the code-gen? Because preempt_count() is > > raw_cpu_read_4() and at least some old compilers will refuse to CSE it > > (consider the this_cpu_read_stable mess). > > I looked at gcc8 and 10 output and the compilers are smart enough to > fold it for the !RT case. But yeah ... If recent GCC is smart enough I suppose it doesn't matter, thanks!
--- a/include/linux/preempt.h +++ b/include/linux/preempt.h @@ -77,31 +77,33 @@ /* preempt_count() and related functions, depends on PREEMPT_NEED_RESCHED */ #include <asm/preempt.h> +#define nmi_count() (preempt_count() & NMI_MASK) #define hardirq_count() (preempt_count() & HARDIRQ_MASK) #define softirq_count() (preempt_count() & SOFTIRQ_MASK) -#define irq_count() (preempt_count() & (HARDIRQ_MASK | SOFTIRQ_MASK \ - | NMI_MASK)) +#define irq_count() (nmi_count() | hardirq_count() | softirq_count()) /* - * Are we doing bottom half or hardware interrupt processing? + * Macros to retrieve the current execution context: * - * in_irq() - We're in (hard) IRQ context + * in_nmi() - We're in NMI context + * in_hardirq() - We're in hard IRQ context + * in_serving_softirq() - We're in softirq context + * in_task() - We're in task context + */ +#define in_nmi() (nmi_count()) +#define in_hardirq() (hardirq_count()) +#define in_serving_softirq() (softirq_count() & SOFTIRQ_OFFSET) +#define in_task() (!(in_nmi() | in_hardirq() | in_serving_softirq())) + +/* + * The following macros are deprecated and should not be used in new code: + * in_irq() - Obsolete version of in_hardirq() * in_softirq() - We have BH disabled, or are processing softirqs * in_interrupt() - We're in NMI,IRQ,SoftIRQ context or have BH disabled - * in_serving_softirq() - We're in softirq context - * in_nmi() - We're in NMI context - * in_task() - We're in task context - * - * Note: due to the BH disabled confusion: in_softirq(),in_interrupt() really - * should not be used in new code. */ #define in_irq() (hardirq_count()) #define in_softirq() (softirq_count()) #define in_interrupt() (irq_count()) -#define in_serving_softirq() (softirq_count() & SOFTIRQ_OFFSET) -#define in_nmi() (preempt_count() & NMI_MASK) -#define in_task() (!(preempt_count() & \ - (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET))) /* * The preempt_count offset after preempt_disable();
Make the macro maze consistent and prepare it for adding the RT variant for BH accounting. - Use nmi_count() for the NMI portion of preempt count - Introduce in_hardirq() to make the naming consistent and non-ambiguos - Use the macros to create combined checks (e.g. in_task()) so the softirq representation for RT just falls into place. - Update comments and move the deprecated macros aside Signed-off-by: Thomas Gleixner <tglx@linutronix.de> --- include/linux/preempt.h | 30 ++++++++++++++++-------------- 1 file changed, 16 insertions(+), 14 deletions(-)