Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754149Ab0H0QlI (ORCPT ); Fri, 27 Aug 2010 12:41:08 -0400 Received: from tx2ehsobe002.messaging.microsoft.com ([65.55.88.12]:42122 "EHLO TX2EHSOBE004.bigfish.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753963Ab0H0QlF (ORCPT ); Fri, 27 Aug 2010 12:41:05 -0400 X-SpamScore: -23 X-BigFish: VPS-23(zzbb2cK1432N1a09M98dN4015Lzz1202hzzz32i2a8h43h61h) X-Spam-TCS-SCL: 0:0 X-FB-SS: 0, X-WSS-ID: 0L7TKWE-01-ASK-02 X-M-MSG: Date: Fri, 27 Aug 2010 18:38:39 +0200 From: Robert Richter To: Will Deacon CC: Matt Fleming , "linux-kernel@vger.kernel.org" , Paul Mundt , Russell King , "linux-arm-kernel@lists.infradead.org" , "linux-sh@vger.kernel.org" , Peter Zijlstra , Ingo Molnar , Frederic Weisbecker , Arnaldo Carvalho de Melo , "linux-arch@vger.kernel.org" Subject: Re: [PATCH 1/4] oprofile: Handle initialisation failure more gracefully Message-ID: <20100827163839.GR22783@erda.amd.com> References: <442a16796990290ca3ebaaa3d0ab317e7b0a30a5.1282848651.git.matt@console-pimps.org> <20100827124344.GJ22783@erda.amd.com> <1282922125.22128.5.camel@e102144-lin.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <1282922125.22128.5.camel@e102144-lin.cambridge.arm.com> User-Agent: Mutt/1.5.20 (2009-06-14) X-Reverse-DNS: unknown Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5173 Lines: 189 On 27.08.10 11:15:25, Will Deacon wrote: > > > The current implementation is not entirely safe in the case that > > > oprofile_arch_init() fails. We need to make sure that we always call > > > exit_driverfs() if we've called init_driverfs(). Also, avoid a potential > > > double free when freeing 'counter_config', e.g. don't free > > > 'counter_config' in both oprofile_arch_init() and oprofile_arch_exit(). I am not sure if it is worth the memory handling code, we could alternativly implement fixed size arrays with MAX_COUNTERS. This would eas it a lot. But, this code will become generic, so we can stick with this implementation. But, cpu varables should be used, maybe with a later patch. > > The root cause that makes this check necessary is that > > oprofile_arch_exit() is called though oprofile_arch_init() failed. We > > should better fix this instead. I have to admit we will then have to > > check all architectural implementations. > > > > I took a look through all of the oprofile_arch_{init,exit} functions > and it looks like only ARM needs fixing. Nobody else does any allocation > here [well, until Matt's unified version comes into play]. Great, many thanks. > How about something like this? This removes the exit call > from the init code and sets pointers to NULL after they have been > freed. We still have to do some checking so that we don't try to > release a NULL perf event: > > diff --git a/arch/arm/oprofile/common.c b/arch/arm/oprofile/common.c > index 0691176..12253eb 100644 > --- a/arch/arm/oprofile/common.c > +++ b/arch/arm/oprofile/common.c > @@ -275,10 +275,12 @@ out: > return ret; > } > > -static void exit_driverfs(void) > +static void __exit exit_driverfs(void) > { > - platform_device_unregister(oprofile_pdev); > - platform_driver_unregister(&oprofile_driver); > + if (!IS_ERR_OR_NULL(oprofile_pdev)) { This check is obsolete here as we do not call oprofile_arch_exit() on failure. > + platform_device_unregister(oprofile_pdev); > + platform_driver_unregister(&oprofile_driver); > + } > } > #else > static int __init init_driverfs(void) { return 0; } > @@ -365,6 +367,7 @@ int __init oprofile_arch_init(struct > oprofile_operations *ops) > ret = init_driverfs(); > if (ret) { > kfree(counter_config); > + counter_config = NULL; Dito, obsolete now. > return ret; > } > > @@ -374,8 +377,10 @@ int __init oprofile_arch_init(struct > oprofile_operations *ops) > if (!perf_events[cpu]) { > pr_info("oprofile: failed to allocate %d perf events " > "for cpu %d\n", perf_num_counters, cpu); > - while (--cpu >= 0) > + while (--cpu >= 0) { > kfree(perf_events[cpu]); > + perf_events[cpu] = NULL; > + } counter_config must be freed here. > return -ENOMEM; > } > } > @@ -396,25 +401,27 @@ int __init oprofile_arch_init(struct > oprofile_operations *ops) > return ret; > } > > -void oprofile_arch_exit(void) > +void __exit oprofile_arch_exit(void) > { > int cpu, id; > struct perf_event *event; > > - if (*perf_events) { > - exit_driverfs(); > - for_each_possible_cpu(cpu) { > - for (id = 0; id < perf_num_counters; ++id) { > - event = perf_events[cpu][id]; > - if (event != NULL) > - perf_event_release_kernel(event); > - } > - kfree(perf_events[cpu]); > + exit_driverfs(); If we shutdown all this in reverse order, this should be after the loop. > + > + for_each_possible_cpu(cpu) { > + if (!perf_events[cpu]) > + continue; Should be never NULL, the check can be removed. > + > + for (id = 0; id < perf_num_counters; ++id) { > + event = perf_events[cpu][id]; > + if (event != NULL) if (event) ... > + perf_event_release_kernel(event); > } > + > + kfree(perf_events[cpu]); > } > > - if (counter_config) > - kfree(counter_config); > + kfree(counter_config); > } > #else > int __init oprofile_arch_init(struct oprofile_operations *ops) > @@ -422,5 +429,5 @@ int __init oprofile_arch_init(struct > oprofile_operations *ops) > pr_info("oprofile: hardware counters not available\n"); > return -ENODEV; > } > -void oprofile_arch_exit(void) {} > +void __exit oprofile_arch_exit(void) {} > #endif /* CONFIG_HW_PERF_EVENTS */ > diff --git a/drivers/oprofile/oprof.c b/drivers/oprofile/oprof.c > index b336cd9..3094af0 100644 > --- a/drivers/oprofile/oprof.c > +++ b/drivers/oprofile/oprof.c > @@ -257,15 +257,11 @@ static int __init oprofile_init(void) > printk(KERN_INFO "oprofile: using timer interrupt.\n"); > err = oprofile_timer_init(&oprofile_ops); > if (err) > - goto out_arch; > + goto out; A 'return err;' here would remove the goto. I would preffer this. Thanks, -Robert > } > err = oprofilefs_register(); > - if (err) > - goto out_arch; > - return 0; > > -out_arch: > - oprofile_arch_exit(); > +out: > return err; > } > > > Thanks, > > Will > > -- Advanced Micro Devices, Inc. Operating System Research Center -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/