| Message ID | 20160811152538.GH13300@pathway.suse.cz (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, Aug 11, 2016 at 05:25:38PM +0200, Petr Mladek wrote: > diff --git a/arch/x86/include/asm/irqflags.h b/arch/x86/include/asm/irqflags.h > index b77f5edb03b0..e31d50acd491 100644 > --- a/arch/x86/include/asm/irqflags.h > +++ b/arch/x86/include/asm/irqflags.h > @@ -44,7 +44,7 @@ static inline void native_irq_enable(void) > asm volatile("sti": : :"memory"); > } > > -static inline void native_safe_halt(void) > +static inline __attribute__((__section__(".cpuidle.text"))) void native_safe_halt(void) > { > asm volatile("sti; hlt": : :"memory"); > } An alternative is to use __always_inline I suppose.
On 8/11/2016 11:25 AM, Petr Mladek wrote: > On Mon 2016-08-08 12:03:38, Chris Metcalf wrote: >>>> When doing an nmi backtrace of many cores, most of which are idle, >>>> the output is a little overwhelming and very uninformative. Suppress >>>> messages for cpus that are idling when they are interrupted and just >>>> emit one line, "NMI backtrace for N skipped: idling at pc 0xNNN". > Hmm, the problem is that native_safe_halt() is called from default_idle() > here. The function is marked as inline but the compiler did not inline > it. > > It helped me to put native_safe_halt() into the __cpuidle_text section: Following Peter Z's suggestion, I have added an __always_inline marker to native_safe_halt. For consistency, I also did arch_safe_halt(), since that invokes native_safe_halt, and then also native_halt() and halt(), so that we're not being weirdly inconsistent with markings for halt inlines. There are also the native_irq_enable(), etc., accessors in that same header that are still only marked "inline" not "always_inline", but I wanted to stop before I was touching too much unrelated code. > I wonder if it would be possible to detect the idle thread an other > way. For example, I wonder if it would be enough to check for the > PID 0. No, the problem is that pid 0 can also go off and run "interesting" code for things like power management, etc., so we really just want to focus on being quite sure that the running code isn't interesting before we suppress the backtrace information. See the thread around here: https://lkml.kernel.org/r/20160307204317.GR6344@twins.programming.kicks-ass.net
On Mon 2016-08-15 12:41:54, Chris Metcalf wrote: > On 8/11/2016 11:25 AM, Petr Mladek wrote: > >On Mon 2016-08-08 12:03:38, Chris Metcalf wrote: > >>>>When doing an nmi backtrace of many cores, most of which are idle, > >>>>the output is a little overwhelming and very uninformative. Suppress > >>>>messages for cpus that are idling when they are interrupted and just > >>>>emit one line, "NMI backtrace for N skipped: idling at pc 0xNNN". > >Hmm, the problem is that native_safe_halt() is called from default_idle() > >here. The function is marked as inline but the compiler did not inline > >it. > > > >It helped me to put native_safe_halt() into the __cpuidle_text section: > > Following Peter Z's suggestion, I have added an __always_inline marker > to native_safe_halt. For consistency, I also did arch_safe_halt(), since that > invokes native_safe_halt, and then also native_halt() and halt(), so that > we're not being weirdly inconsistent with markings for halt inlines. > > There are also the native_irq_enable(), etc., accessors in that same header > that are still only marked "inline" not "always_inline", but I wanted to stop > before I was touching too much unrelated code. Sounds fine. > >I wonder if it would be possible to detect the idle thread an other > >way. For example, I wonder if it would be enough to check for the > >PID 0. > > No, the problem is that pid 0 can also go off and run "interesting" code > for things like power management, etc., so we really just want to > focus on being quite sure that the running code isn't interesting before > we suppress the backtrace information. > > See the thread around here: > > https://lkml.kernel.org/r/20160307204317.GR6344@twins.programming.kicks-ass.net Makes sense. Thanks for the poitner. Best Regards, Petr
diff --git a/arch/x86/include/asm/irqflags.h b/arch/x86/include/asm/irqflags.h index b77f5edb03b0..e31d50acd491 100644 --- a/arch/x86/include/asm/irqflags.h +++ b/arch/x86/include/asm/irqflags.h @@ -44,7 +44,7 @@ static inline void native_irq_enable(void) asm volatile("sti": : :"memory"); } -static inline void native_safe_halt(void) +static inline __attribute__((__section__(".cpuidle.text"))) void native_safe_halt(void) { asm volatile("sti; hlt": : :"memory"); }