From: Mathieu Poirier <mathieu.poirier@linaro.org> To: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org> Cc: Peter Zijlstra <peterz@infradead.org>, Suzuki Poulose <suzuki.poulose@arm.com>, Mike Leach <mike.leach@linaro.org>, Ingo Molnar <mingo@redhat.com>, Arnaldo Carvalho de Melo <acme@kernel.org>, Mark Rutland <mark.rutland@arm.com>, Alexander Shishkin <alexander.shishkin@linux.intel.com>, Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>, coresight@lists.linaro.org, Stephen Boyd <swboyd@chromium.org>, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCHv2 2/4] coresight: tmc-etf: Fix NULL ptr dereference in tmc_enable_etf_sink_perf() Date: Wed, 4 Nov 2020 10:03:35 -0700 [thread overview] Message-ID: <20201104170335.GA2892592@xps15> (raw) In-Reply-To: <85c285361ce1c71b1a8274493aab9ca7@codeaurora.org> On Fri, Oct 30, 2020 at 10:56:09PM +0530, Sai Prakash Ranjan wrote: > Hi Mathieu, > > On 2020-10-30 22:18, Mathieu Poirier wrote: > > On Fri, Oct 30, 2020 at 01:29:56PM +0530, Sai Prakash Ranjan wrote: > > > Hello guys, > > > > > > On 2020-10-24 02:07, Mathieu Poirier wrote: > > > > On Fri, Oct 23, 2020 at 03:44:16PM +0200, Peter Zijlstra wrote: > > > > > On Fri, Oct 23, 2020 at 02:29:54PM +0100, Suzuki Poulose wrote: > > > > > > On 10/23/20 2:16 PM, Peter Zijlstra wrote: > > > > > > > On Fri, Oct 23, 2020 at 01:56:47PM +0100, Suzuki Poulose wrote: > > > > > > > > > > > > > That way another session could use the same sink if it is free. i.e > > > > > > > > > > > > > > > > perf record -e cs_etm/@sink0/u --per-thread app1 > > > > > > > > > > > > > > > > and > > > > > > > > > > > > > > > > perf record -e cs_etm/@sink0/u --per-thread app2 > > > > > > > > > > > > > > > > both can work as long as the sink is not used by the other session. > > > > > > > > > > > > > > Like said above, if sink is shared between CPUs, that's going to be a > > > > > > > trainwreck :/ Why do you want that? > > > > > > > > > > > > That ship has sailed. That is how the current generation of systems are, > > > > > > unfortunately. But as I said, this is changing and there are guidelines > > > > > > in place to avoid these kind of topologies. With the future > > > > > > technologies, this will be completely gone. > > > > > > > > > > I understand that the hardware is like that, but why do you want to > > > > > support this insanity in software? > > > > > > > > > > If you only allow a single sink user (group) at the same time, your > > > > > problem goes away. Simply disallow the above scenario, do not allow > > > > > concurrent sink users if sinks are shared like this. > > > > > > > > > > Have the perf-record of app2 above fail because the sink is in-user > > > > > already. > > > > > > > > I agree with you that --per-thread scenarios are easy to deal with, but > > > > to > > > > support cpu-wide scenarios events must share a sink (because there is > > > > one event > > > > per CPU). CPU-wide support can't be removed because it has been around > > > > for close to a couple of years and heavily used. I also think using the > > > > pid of > > > > the process that created the events, i.e perf, is a good idea. We just > > > > need to > > > > agree on how to gain access to it. > > > > > > > > In Sai's patch you objected to the following: > > > > > > > > > + struct task_struct *task = READ_ONCE(event->owner); > > > > > + > > > > > + if (!task || is_kernel_event(event)) > > > > > > > > Would it be better to use task_nr_pid(current) instead of event->owner? > > > > The end > > > > result will be exactly the same. There is also no need to check the > > > > validity of > > > > @current since it is a user process. > > > > > > > > > > We have devices deployed where these crashes are seen consistently, > > > so for some immediate relief, could we atleast get some fix in this > > > cycle without major design overhaul which would likely take more time. > > > Perhaps my first patch [1] without any check for owner or > > > I can post a new version as Suzuki suggested [2] dropping the export > > > of is_kernel_event(). Then we can always work on top of it based on > > > the > > > conclusion of this discussion, we will atleast not have the systems > > > crash in the meantime, thoughts? > > > > For the time being I think [1], exactly the way it is, is a reasonable > > way > > forward. > > > > Sure, I just checked now and [1] still applies neatly on top of coresight > next branch. > > [1] https://lore.kernel.org/patchwork/patch/1318098/ I have applied both patches that were part of the set. > > Thanks, > Sai > > -- > QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member > of Code Aurora Forum, hosted by The Linux Foundation
WARNING: multiple messages have this Message-ID (diff)
From: Mathieu Poirier <mathieu.poirier@linaro.org> To: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org> Cc: Mark Rutland <mark.rutland@arm.com>, Suzuki Poulose <suzuki.poulose@arm.com>, Peter Zijlstra <peterz@infradead.org>, linux-arm-msm@vger.kernel.org, coresight@lists.linaro.org, linux-kernel@vger.kernel.org, Arnaldo Carvalho de Melo <acme@kernel.org>, Stephen Boyd <swboyd@chromium.org>, Alexander Shishkin <alexander.shishkin@linux.intel.com>, Ingo Molnar <mingo@redhat.com>, Namhyung Kim <namhyung@kernel.org>, Jiri Olsa <jolsa@redhat.com>, linux-arm-kernel@lists.infradead.org, Mike Leach <mike.leach@linaro.org> Subject: Re: [PATCHv2 2/4] coresight: tmc-etf: Fix NULL ptr dereference in tmc_enable_etf_sink_perf() Date: Wed, 4 Nov 2020 10:03:35 -0700 [thread overview] Message-ID: <20201104170335.GA2892592@xps15> (raw) In-Reply-To: <85c285361ce1c71b1a8274493aab9ca7@codeaurora.org> On Fri, Oct 30, 2020 at 10:56:09PM +0530, Sai Prakash Ranjan wrote: > Hi Mathieu, > > On 2020-10-30 22:18, Mathieu Poirier wrote: > > On Fri, Oct 30, 2020 at 01:29:56PM +0530, Sai Prakash Ranjan wrote: > > > Hello guys, > > > > > > On 2020-10-24 02:07, Mathieu Poirier wrote: > > > > On Fri, Oct 23, 2020 at 03:44:16PM +0200, Peter Zijlstra wrote: > > > > > On Fri, Oct 23, 2020 at 02:29:54PM +0100, Suzuki Poulose wrote: > > > > > > On 10/23/20 2:16 PM, Peter Zijlstra wrote: > > > > > > > On Fri, Oct 23, 2020 at 01:56:47PM +0100, Suzuki Poulose wrote: > > > > > > > > > > > > > That way another session could use the same sink if it is free. i.e > > > > > > > > > > > > > > > > perf record -e cs_etm/@sink0/u --per-thread app1 > > > > > > > > > > > > > > > > and > > > > > > > > > > > > > > > > perf record -e cs_etm/@sink0/u --per-thread app2 > > > > > > > > > > > > > > > > both can work as long as the sink is not used by the other session. > > > > > > > > > > > > > > Like said above, if sink is shared between CPUs, that's going to be a > > > > > > > trainwreck :/ Why do you want that? > > > > > > > > > > > > That ship has sailed. That is how the current generation of systems are, > > > > > > unfortunately. But as I said, this is changing and there are guidelines > > > > > > in place to avoid these kind of topologies. With the future > > > > > > technologies, this will be completely gone. > > > > > > > > > > I understand that the hardware is like that, but why do you want to > > > > > support this insanity in software? > > > > > > > > > > If you only allow a single sink user (group) at the same time, your > > > > > problem goes away. Simply disallow the above scenario, do not allow > > > > > concurrent sink users if sinks are shared like this. > > > > > > > > > > Have the perf-record of app2 above fail because the sink is in-user > > > > > already. > > > > > > > > I agree with you that --per-thread scenarios are easy to deal with, but > > > > to > > > > support cpu-wide scenarios events must share a sink (because there is > > > > one event > > > > per CPU). CPU-wide support can't be removed because it has been around > > > > for close to a couple of years and heavily used. I also think using the > > > > pid of > > > > the process that created the events, i.e perf, is a good idea. We just > > > > need to > > > > agree on how to gain access to it. > > > > > > > > In Sai's patch you objected to the following: > > > > > > > > > + struct task_struct *task = READ_ONCE(event->owner); > > > > > + > > > > > + if (!task || is_kernel_event(event)) > > > > > > > > Would it be better to use task_nr_pid(current) instead of event->owner? > > > > The end > > > > result will be exactly the same. There is also no need to check the > > > > validity of > > > > @current since it is a user process. > > > > > > > > > > We have devices deployed where these crashes are seen consistently, > > > so for some immediate relief, could we atleast get some fix in this > > > cycle without major design overhaul which would likely take more time. > > > Perhaps my first patch [1] without any check for owner or > > > I can post a new version as Suzuki suggested [2] dropping the export > > > of is_kernel_event(). Then we can always work on top of it based on > > > the > > > conclusion of this discussion, we will atleast not have the systems > > > crash in the meantime, thoughts? > > > > For the time being I think [1], exactly the way it is, is a reasonable > > way > > forward. > > > > Sure, I just checked now and [1] still applies neatly on top of coresight > next branch. > > [1] https://lore.kernel.org/patchwork/patch/1318098/ I have applied both patches that were part of the set. > > Thanks, > Sai > > -- > QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member > of Code Aurora Forum, hosted by The Linux Foundation _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2020-11-04 17:03 UTC|newest] Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-10-22 10:57 [PATCHv2 0/4] coresight: etf/etb10/etr: Fix NULL pointer dereference crashes Sai Prakash Ranjan 2020-10-22 10:57 ` Sai Prakash Ranjan 2020-10-22 10:57 ` [PATCHv2 1/4] perf/core: Export is_kernel_event() Sai Prakash Ranjan 2020-10-22 10:57 ` Sai Prakash Ranjan 2020-10-31 7:35 ` kernel test robot 2020-10-22 10:57 ` [PATCHv2 2/4] coresight: tmc-etf: Fix NULL ptr dereference in tmc_enable_etf_sink_perf() Sai Prakash Ranjan 2020-10-22 10:57 ` Sai Prakash Ranjan 2020-10-22 11:32 ` Peter Zijlstra 2020-10-22 11:32 ` Peter Zijlstra 2020-10-22 12:49 ` Sai Prakash Ranjan 2020-10-22 12:49 ` Sai Prakash Ranjan 2020-10-22 13:34 ` Peter Zijlstra 2020-10-22 13:34 ` Peter Zijlstra 2020-10-22 14:23 ` Sai Prakash Ranjan 2020-10-22 14:23 ` Sai Prakash Ranjan 2020-10-22 13:30 ` Suzuki Poulose 2020-10-22 13:30 ` Suzuki Poulose 2020-10-22 15:06 ` Peter Zijlstra 2020-10-22 15:06 ` Peter Zijlstra 2020-10-22 15:32 ` Suzuki Poulose 2020-10-22 15:32 ` Suzuki Poulose 2020-10-22 21:20 ` Mathieu Poirier 2020-10-22 21:20 ` Mathieu Poirier 2020-10-23 7:39 ` Peter Zijlstra 2020-10-23 7:39 ` Peter Zijlstra 2020-10-23 8:49 ` Suzuki Poulose 2020-10-23 8:49 ` Suzuki Poulose 2020-10-23 9:23 ` Peter Zijlstra 2020-10-23 9:23 ` Peter Zijlstra 2020-10-23 10:49 ` Suzuki Poulose 2020-10-23 10:49 ` Suzuki Poulose 2020-10-23 9:41 ` Peter Zijlstra 2020-10-23 9:41 ` Peter Zijlstra 2020-10-23 10:34 ` Suzuki Poulose 2020-10-23 10:34 ` Suzuki Poulose 2020-10-23 10:54 ` Peter Zijlstra 2020-10-23 10:54 ` Peter Zijlstra 2020-10-23 12:56 ` Suzuki Poulose 2020-10-23 12:56 ` Suzuki Poulose 2020-10-23 13:16 ` Peter Zijlstra 2020-10-23 13:16 ` Peter Zijlstra 2020-10-23 13:29 ` Suzuki Poulose 2020-10-23 13:29 ` Suzuki Poulose 2020-10-23 13:44 ` Peter Zijlstra 2020-10-23 13:44 ` Peter Zijlstra 2020-10-23 20:37 ` Mathieu Poirier 2020-10-23 20:37 ` Mathieu Poirier 2020-10-30 7:59 ` Sai Prakash Ranjan 2020-10-30 7:59 ` Sai Prakash Ranjan 2020-10-30 16:48 ` Mathieu Poirier 2020-10-30 16:48 ` Mathieu Poirier 2020-10-30 17:26 ` Sai Prakash Ranjan 2020-10-30 17:26 ` Sai Prakash Ranjan 2020-11-04 17:03 ` Mathieu Poirier [this message] 2020-11-04 17:03 ` Mathieu Poirier 2020-10-22 10:57 ` [PATCHv2 3/4] coresight: etb10: Fix possible NULL ptr dereference in etb_enable_perf() Sai Prakash Ranjan 2020-10-22 10:57 ` Sai Prakash Ranjan 2020-10-22 10:57 ` [PATCHv2 4/4] coresight: tmc-etr: Fix possible NULL ptr dereference in get_perf_etr_buf_cpu_wide() Sai Prakash Ranjan 2020-10-22 10:57 ` Sai Prakash Ranjan 2020-10-22 11:10 ` [PATCHv2 0/4] coresight: etf/etb10/etr: Fix NULL pointer dereference crashes Sai Prakash Ranjan 2020-10-22 11:10 ` Sai Prakash Ranjan 2020-10-22 11:23 ` Sai Prakash Ranjan 2020-10-22 11:23 ` Sai Prakash Ranjan
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