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[68.147.8.254]) by smtp.gmail.com with ESMTPSA id s8sm4057359pfm.180.2020.09.03.10.47.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 03 Sep 2020 10:47:18 -0700 (PDT) Date: Thu, 3 Sep 2020 11:47:16 -0600 From: Mathieu Poirier To: Suzuki K Poulose Subject: Re: [PATCH v2] coresight: etm4x: Handle unreachable sink in perf mode Message-ID: <20200903174716.GD312784@xps15> References: <20200902152847.195909-1-suzuki.poulose@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200902152847.195909-1-suzuki.poulose@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200903_134721_464416_4A84EAC2 X-CRM114-Status: GOOD ( 26.21 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: coresight@lists.linaro.org, Mike Leach , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, jeremy.linton@arm.com Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Sep 02, 2020 at 04:28:47PM +0100, Suzuki K Poulose wrote: > If the specified/hinted sink is not reachable from a subset of the CPUs, > we could end up unable to trace the event on those CPUs. This > is the best effort we could do until we support 1:1 configurations. > Fail gracefully in such cases avoiding a WARN_ON, which can be easily > triggered by the user on certain platforms (Arm N1SDP), with the following > trace paths : > > CPU0 > \ > -- Funnel0 --> ETF0 --> > / \ > CPU1 \ > MainFunnel > CPU2 / > \ / > -- Funnel1 --> ETF1 --> > / > CPU1 > > $ perf record --per-thread -e cs_etm/@ETF0/u -- > > could trigger the following WARNING, when the event is scheduled > on CPU2. > > [10919.513250] ------------[ cut here ]------------ > [10919.517861] WARNING: CPU: 2 PID: 24021 at > drivers/hwtracing/coresight/coresight-etm-perf.c:316 etm_event_start+0xf8/0x100 > ... > > [10919.564403] CPU: 2 PID: 24021 Comm: perf Not tainted 5.8.0+ #24 > [10919.570308] pstate: 80400089 (Nzcv daIf +PAN -UAO BTYPE=--) > [10919.575865] pc : etm_event_start+0xf8/0x100 > [10919.580034] lr : etm_event_start+0x80/0x100 > [10919.584202] sp : fffffe001932f940 > [10919.587502] x29: fffffe001932f940 x28: fffffc834995f800 > [10919.592799] x27: 0000000000000000 x26: fffffe0011f3ced0 > [10919.598095] x25: fffffc837fce244c x24: fffffc837fce2448 > [10919.603391] x23: 0000000000000002 x22: fffffc8353529c00 > [10919.608688] x21: fffffc835bb31000 x20: 0000000000000000 > [10919.613984] x19: fffffc837fcdcc70 x18: 0000000000000000 > [10919.619281] x17: 0000000000000000 x16: 0000000000000000 > [10919.624577] x15: 0000000000000000 x14: 00000000000009f8 > [10919.629874] x13: 00000000000009f8 x12: 0000000000000018 > [10919.635170] x11: 0000000000000000 x10: 0000000000000000 > [10919.640467] x9 : fffffe00108cd168 x8 : 0000000000000000 > [10919.645763] x7 : 0000000000000020 x6 : 0000000000000001 > [10919.651059] x5 : 0000000000000002 x4 : 0000000000000001 > [10919.656356] x3 : 0000000000000000 x2 : 0000000000000000 > [10919.661652] x1 : fffffe836eb40000 x0 : 0000000000000000 > [10919.666949] Call trace: > [10919.669382] etm_event_start+0xf8/0x100 > [10919.673203] etm_event_add+0x40/0x60 > [10919.676765] event_sched_in.isra.134+0xcc/0x210 > [10919.681281] merge_sched_in+0xb0/0x2a8 > [10919.685017] visit_groups_merge.constprop.140+0x15c/0x4b8 > [10919.690400] ctx_sched_in+0x15c/0x170 > [10919.694048] perf_event_sched_in+0x6c/0xa0 > [10919.698130] ctx_resched+0x60/0xa0 > [10919.701517] perf_event_exec+0x288/0x2f0 > [10919.705425] begin_new_exec+0x4c8/0xf58 > [10919.709247] load_elf_binary+0x66c/0xf30 > [10919.713155] exec_binprm+0x15c/0x450 > [10919.716716] __do_execve_file+0x508/0x748 > [10919.720711] __arm64_sys_execve+0x40/0x50 > [10919.724707] do_el0_svc+0xf4/0x1b8 > [10919.728095] el0_sync_handler+0xf8/0x124 > [10919.732003] el0_sync+0x140/0x180 > > Even though we don't support using separate sinks for the ETMs yet (e.g, > for 1:1 configurations), we should at least honor the user's choice and > handle the limitations gracefully, by simply skipping the tracing on ETMs > which can't reach the requested sink. > > Fixes: f9d81a657bb8 ("coresight: perf: Allow tracing on hotplugged CPUs") > Reported-by: Jeremy Linton > Tested-by: Jeremy Linton > Cc: Mathieu Poirier > Cc: Mike Leach > Signed-off-by: Suzuki K Poulose I have applied your patch. Thanks, Mathieu > --- > Change since v1: > - Updated the description, added Tested-by. > - No code changes > - Rebased on coresight/next > --- > drivers/hwtracing/coresight/coresight-etm-perf.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c > index 1a3169e69bb1..9d61a71da96f 100644 > --- a/drivers/hwtracing/coresight/coresight-etm-perf.c > +++ b/drivers/hwtracing/coresight/coresight-etm-perf.c > @@ -321,6 +321,16 @@ static void etm_event_start(struct perf_event *event, int flags) > if (!event_data) > goto fail; > > + /* > + * Check if this ETM is allowed to trace, as decided > + * at etm_setup_aux(). This could be due to an unreachable > + * sink from this ETM. We can't do much in this case if > + * the sink was specified or hinted to the driver. For > + * now, simply don't record anything on this ETM. > + */ > + if (!cpumask_test_cpu(cpu, &event_data->mask)) > + goto fail_end_stop; > + > path = etm_event_cpu_path(event_data, cpu); > /* We need a sink, no need to continue without one */ > sink = coresight_get_sink(path); > -- > 2.24.1 > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel