From: Anshuman Khandual <anshuman.khandual@arm.com>
To: Suzuki K Poulose <suzuki.poulose@arm.com>, coresight@lists.linaro.org
Cc: linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, tamas.zsoldos@arm.com,
al.grant@arm.com, leo.yan@linaro.org, mike.leach@linaro.org,
mathieu.poirier@linaro.org, jinlmao@qti.qualcomm.com
Subject: Re: [PATCH v2 03/10] coresight: etm-pmu: Ensure the AUX handle is valid
Date: Fri, 30 Jul 2021 09:44:31 +0530 [thread overview]
Message-ID: <acd70df3-fdce-a08c-02f0-4cd6d806e6ba@arm.com> (raw)
In-Reply-To: <20210723124611.3828908-4-suzuki.poulose@arm.com>
On 7/23/21 6:16 PM, Suzuki K Poulose wrote:
> The ETM perf infrastructure closes out a handle during event_stop
> or on an error in starting the event. In either case, it is possible
> for a "sink" to update/close the handle, under certain circumstances.
> (e.g no space in ring buffer.). So, ensure that we handle this
> gracefully in the PMU driver by verifying the handle is still valid.
>
> Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
> Cc: Mike Leach <mike.leach@linaro.org>
> Cc: Anshuman Khandual <anshuman.khandual@arm.com>
> Cc: Leo Yan <leo.yan@linaro.org>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> ---
> .../hwtracing/coresight/coresight-etm-perf.c | 27 ++++++++++++++++---
> 1 file changed, 24 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c
> index 6f398377fec9..a6ab603afee4 100644
> --- a/drivers/hwtracing/coresight/coresight-etm-perf.c
> +++ b/drivers/hwtracing/coresight/coresight-etm-perf.c
> @@ -450,8 +450,15 @@ static void etm_event_start(struct perf_event *event, int flags)
> fail_disable_path:
> coresight_disable_path(path);
> fail_end_stop:
> - perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED);
> - perf_aux_output_end(handle, 0);
> + /*
> + * Check if the handle is still associated with the event,
> + * to handle cases where if the sink failed to start the
> + * trace and TRUNCATED the handle already.
> + */
> + if (READ_ONCE(handle->event)) {
> + perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED);
> + perf_aux_output_end(handle, 0);
> + }
Makes sense as perf_aux_output_[flag|end]() helpers do not
validate the 'handle' themselves.
> fail:
> event->hw.state = PERF_HES_STOPPED;
> goto out;
> @@ -519,7 +526,21 @@ static void etm_event_stop(struct perf_event *event, int mode)
>
> size = sink_ops(sink)->update_buffer(sink, handle,
> event_data->snk_config);
> - perf_aux_output_end(handle, size);
> + /*
> + * Make sure the handle is still valid as the
> + * sink could have closed it from an IRQ.
> + * The sink driver must handle the race with
> + * update_buffer() and IRQ. Thus either we
> + * should get a valid handle and valid size
> + * (which may be 0).
> + *
> + * But we should never get a non-zero size with
> + * an invalid handle.
> + */
> + if (READ_ONCE(handle->event))
> + perf_aux_output_end(handle, size);
> + else
> + WARN_ON(size);
Right.
> }
>
> /* Disabling the path make its elements available to other sessions */
>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
next prev parent reply other threads:[~2021-07-30 4:13 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-23 12:46 [PATCH v2 00/10] coresight: TRBE and Self-Hosted trace fixes Suzuki K Poulose
2021-07-23 12:46 ` [PATCH v2 01/10] coresight: etm4x: Save restore TRFCR_EL1 Suzuki K Poulose
2021-07-30 3:05 ` Anshuman Khandual
2021-07-23 12:46 ` [PATCH v2 02/10] coresight: etm4x: Use Trace Filtering controls dynamically Suzuki K Poulose
2021-07-30 3:48 ` Anshuman Khandual
2021-07-30 11:29 ` Suzuki K Poulose
2021-07-23 12:46 ` [PATCH v2 03/10] coresight: etm-pmu: Ensure the AUX handle is valid Suzuki K Poulose
2021-07-30 4:14 ` Anshuman Khandual [this message]
2021-07-23 12:46 ` [PATCH v2 04/10] coresight: trbe: Ensure the format flag is set on truncation Suzuki K Poulose
2021-07-30 4:26 ` Anshuman Khandual
2021-07-30 11:37 ` Suzuki K Poulose
2021-07-23 12:46 ` [PATCH v2 05/10] coresight: trbe: Drop duplicate TRUNCATE flags Suzuki K Poulose
2021-07-30 4:47 ` Anshuman Khandual
2021-07-30 12:58 ` Suzuki K Poulose
2021-07-23 12:46 ` [PATCH v2 06/10] coresight: trbe: Fix handling of spurious interrupts Suzuki K Poulose
2021-07-30 5:15 ` Anshuman Khandual
2021-07-30 12:57 ` Suzuki K Poulose
2021-07-23 12:46 ` [PATCH v2 07/10] coresight: trbe: Do not truncate buffer on IRQ Suzuki K Poulose
2021-07-26 12:34 ` Mike Leach
2021-07-26 16:01 ` Suzuki K Poulose
2021-07-27 10:46 ` Mike Leach
2021-07-27 13:06 ` Suzuki K Poulose
2021-07-28 9:25 ` Suzuki K Poulose
2021-07-23 12:46 ` [PATCH v2 08/10] coresight: trbe: Unify the enabling sequence Suzuki K Poulose
2021-07-30 5:40 ` Anshuman Khandual
2021-07-23 12:46 ` [PATCH v2 09/10] coresight: trbe: End the AUX handle on truncation Suzuki K Poulose
2021-07-30 5:54 ` Anshuman Khandual
2021-07-23 12:46 ` [PATCH v2 10/10] coresight: trbe: Prohibit trace before disabling TRBE Suzuki K Poulose
2021-07-30 6:58 ` Anshuman Khandual
2021-07-23 13:45 ` [PATCH v2 00/10] coresight: TRBE and Self-Hosted trace fixes Suzuki K Poulose
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