On Wed, 18 Jul 2007, Al Viro wrote:
> On Wed, Jul 18, 2007 at 01:24:46AM +0200, Uwe Kleine-Konig wrote: > > [...] > > a52b1752c07 introduces usage of the WARN_ON macro in <linux/smp.h>, but > > doesn't pull in <linux/kernel.h>. (<asm/bug.h> is not enough, at least > > for arm, because WARN_ON uses printk there.) > > > > The obvious options are: > > > > 1) include <linux/kernel.h> in <linux/smp.h>, maybe conditioned by !SMP > > 2) include <linux/kernel.h> in all includers of <linux/smp.h> > > 3) remove the WARN_ONs introduced by a52b1752c07. > > [...] > > 4) turn the sucker into macro I think that warning is incorrect anyway ... and I'm to blame for that. What happened is that I had earlier (month or two back, _before_ the recent change in smp_call_function_single() semantics) submitted a patch that put an unconditional WARN_ON(1) in this function for UP -- in those days, both the smp_call_function* variants were illegal on the current CPU itself. ( http://lkml.org/lkml/2007/6/7/262 ) Then recently, Andi / Avi proposed the new semantics for smp_call_function_single() to allow it to just execute the given function on current CPU as well -- smp_call_function() semantics were left unchanged, so as not to break stuff like smp_send_stop(). I think I got confused and recommended the (cpuid != 0) warning, but I don't really think it is necessary with new semantics -- sorry about this, Avi. OTOH, the function _should_ include a WARN_ON, but for a different condition -- irqs_disabled(), as explained in changelog below. I'd be grateful if someone could apply this, Cc:'ing Andi too. Satyam --- [PATCH] UP: smp_call_function_single() must warn on irqs_disabled() Because: (1) smp_call_function_single() semantics dictate that. (2) That makes UP behaviour similar to SMP case (implementations of smp_call_function_single() in all the archs do this). (3) We use the unconditional non-save/restore-flags versions of local_irq_disable/enable just below this, so it's a bug to call this function with IRQs disabled anyway. Also remove the cpuid != 0 warning that I had erroneously suggested to Avi earlier (sorry!) Signed-off-by: Satyam Sharma <[EMAIL PROTECTED]> Cc: Andi Kleen <[EMAIL PROTECTED]> Cc: Avi Kivity <[EMAIL PROTECTED]> --- include/linux/smp.h | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/include/linux/smp.h b/include/linux/smp.h index 259a13c..016dab5 100644 --- a/include/linux/smp.h +++ b/include/linux/smp.h @@ -101,7 +101,7 @@ static inline void smp_send_reschedule(int cpu) { } #define smp_prepare_boot_cpu() do {} while (0) #define smp_call_function_single(cpuid, func, info, retry, wait) \ ({ \ - WARN_ON(cpuid != 0); \ + WARN_ON(irqs_disabled()); \ local_irq_disable(); \ (func)(info); \ local_irq_enable(); \ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
