From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756062Ab2HORiX (ORCPT ); Wed, 15 Aug 2012 13:38:23 -0400 Received: from e28smtp01.in.ibm.com ([122.248.162.1]:34478 "EHLO e28smtp01.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755976Ab2HORiW (ORCPT ); Wed, 15 Aug 2012 13:38:22 -0400 Message-ID: <502BDE3D.6070909@linux.vnet.ibm.com> Date: Wed, 15 Aug 2012 23:07:01 +0530 From: "Naveen N. Rao" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:14.0) Gecko/20120717 Thunderbird/14.0 MIME-Version: 1.0 To: fweisbec@gmail.com CC: a.p.zijlstra@chello.nl, prasad.krishnan@gmail.com, linux-kernel@vger.kernel.org, mingo@redhat.com, paulus@samba.org, acme@ghostprotocols.net, emachado@linux.vnet.ibm.com Subject: Re: [PATCH v3] Hardware breakpoints: Invoke __perf_event_disable() if interrupts are already disabled References: <20120731134124.GD17078@somewhere.redhat.com> <20120802081635.5811.17737.stgit@localhost.localdomain> In-Reply-To: <20120802081635.5811.17737.stgit@localhost.localdomain> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit x-cbid: 12081517-4790-0000-0000-00000425FE58 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Frederick, Did you get a chance to take a look at this? Regards, Naveen On 08/02/2012 01:46 PM, Naveen N. Rao wrote: > Hi Frederick, > I've added a check to make sure we are targeting the current task. This > applies on top of v3.5. Kindly review. > > Thanks, > Naveen > > History: > v3: Added check to make sure we only target "current" task. > v2: Use __perf_event_disable() directly > ______ > > From: K.Prasad > > 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 > Signed-off-by: K.Prasad > [naveen.n.rao@linux.vnet.ibm.com: v3: Check to make sure we target current task] > Signed-off-by: Naveen N. Rao > --- > include/linux/perf_event.h | 2 ++ > kernel/events/core.c | 2 +- > kernel/events/hw_breakpoint.c | 11 ++++++++++- > 3 files changed, 13 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..9a7b487 100644 > --- a/kernel/events/hw_breakpoint.c > +++ b/kernel/events/hw_breakpoint.c > @@ -453,7 +453,16 @@ 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 after making sure we are targeting the > + * current task. > + */ > + if (irqs_disabled() && bp->ctx && bp->ctx->task == current) > + __perf_event_disable(bp); > + else > + perf_event_disable(bp); > > bp->attr.bp_addr = attr->bp_addr; > bp->attr.bp_type = attr->bp_type; >