On Wed, Jul 18, 2012 at 04:00:46PM +0530, Naveen N. Rao wrote: > Please find v2 of the patch from Prasad, based on Peter Zijlstra's > feedback. This applies on top of v3.5-rc7. This has been tested and > found to work fine by Edjunior. > > Regards, > Naveen > ______ > > From: K.Prasad <[email protected]> > > While debugging a warning message on PowerPC while using hardware > breakpoints, it was discovered that when perf_event_disable is invoked > through hw_breakpoint_handler function with interrupts disabled, a > subsequent IPI in the code path would trigger a WARN_ON_ONCE message in > smp_call_function_single function. > > This patch calls __perf_event_disable() when interrupts are already > disabled, instead of perf_event_disable(). > > Reported-by: Edjunior Barbosa Machado <[email protected]> > Signed-off-by: K.Prasad <[email protected]> > Signed-off-by: Naveen N. Rao <[email protected]> > --- > include/linux/perf_event.h | 2 ++ > kernel/events/core.c | 2 +- > kernel/events/hw_breakpoint.c | 10 +++++++++- > 3 files changed, 12 insertions(+), 2 deletions(-) > > diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h > index 45db49f..c289ba0 100644 > --- a/include/linux/perf_event.h > +++ b/include/linux/perf_event.h > @@ -1292,6 +1292,7 @@ extern int perf_swevent_get_recursion_context(void); > extern void perf_swevent_put_recursion_context(int rctx); > extern void perf_event_enable(struct perf_event *event); > extern void perf_event_disable(struct perf_event *event); > +extern int __perf_event_disable(void *info); > extern void perf_event_task_tick(void); > #else > static inline void > @@ -1330,6 +1331,7 @@ static inline int > perf_swevent_get_recursion_context(void) { return -1; } > static inline void perf_swevent_put_recursion_context(int rctx) > { } > static inline void perf_event_enable(struct perf_event *event) > { } > static inline void perf_event_disable(struct perf_event *event) > { } > +static inline int __perf_event_disable(void *info) { } > static inline void perf_event_task_tick(void) > { } > #endif > > diff --git a/kernel/events/core.c b/kernel/events/core.c > index d7d71d6..0ad0fc9 100644 > --- a/kernel/events/core.c > +++ b/kernel/events/core.c > @@ -1253,7 +1253,7 @@ retry: > /* > * Cross CPU call to disable a performance event > */ > -static int __perf_event_disable(void *info) > +int __perf_event_disable(void *info) > { > struct perf_event *event = info; > struct perf_event_context *ctx = event->ctx; > diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c > index bb38c4d..483f14a 100644 > --- a/kernel/events/hw_breakpoint.c > +++ b/kernel/events/hw_breakpoint.c > @@ -453,7 +453,15 @@ int modify_user_hw_breakpoint(struct perf_event *bp, > struct perf_event_attr *att > int old_type = bp->attr.bp_type; > int err = 0; > > - perf_event_disable(bp); > + /* > + * modify_user_hw_breakpoint can be invoked with IRQs disabled and > hence it > + * will not be possible to raise IPIs that invoke __perf_event_disable. > + * So call the function directly. > + */ > + if (irqs_disabled()) > + __perf_event_disable(bp); > + else > + perf_event_disable(bp);
This only works if we are sure the bp is on the current CPU. Do we have that guarantee? > > bp->attr.bp_addr = attr->bp_addr; > bp->attr.bp_type = attr->bp_type; > -- 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/
