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SubjectRe: [PATCH 4/5] coresight: trbe: Move irq_work queue processing
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On 7/12/21 5:08 PM, Suzuki K Poulose wrote:
> The TRBE driver issues the irq_work_run() to ensure that
> any pending disable event callback has been processed. But this
> is done before we mark the AUX buffer as TRUNCATED, making
> the call pointless. Move the call after the current handle
> has been closed.

So there is a possibility that a disable event gets missed before
the buffer is marked TRUNCATED ? But even then would not another
disable event be triggered again subsequently ? Just trying to
understand what is the actual problem because of the current
placement of irq_work_run() ?

>
> Fixes: 3fbf7f011f24 ("coresight: sink: Add TRBE driver")
> Reported-by: Tamas Zsoldos <Tamas.Zsoldos@arm.com>
> Cc: Anshuman Khandual <anshuman.khandual@arm.com>
> Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
> Cc: Mike Leach <mike.leach@linaro.org>
> Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
> Cc: Leo Yan <leo.yan@linaro.org>
> Cc: Will Deacon <will@kernel.org>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> ---
> drivers/hwtracing/coresight/coresight-trbe.c | 14 ++++++++------
> 1 file changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-trbe.c b/drivers/hwtracing/coresight/coresight-trbe.c
> index ec38cf17b693..c0c264264427 100644
> --- a/drivers/hwtracing/coresight/coresight-trbe.c
> +++ b/drivers/hwtracing/coresight/coresight-trbe.c
> @@ -723,6 +723,14 @@ static void trbe_handle_overflow(struct perf_output_handle *handle)
> perf_aux_output_flag(handle, PERF_AUX_FLAG_CORESIGHT_FORMAT_RAW |
> PERF_AUX_FLAG_TRUNCATED);
> perf_aux_output_end(handle, size);
> +
> + /*
> + * Ensure perf callbacks have completed. Since we
> + * always TRUNCATE the buffer on IRQ, the event
> + * is scheduled to be disabled. Make sure that happens
> + * as soon as possible.
> + */
> + irq_work_run();
> }
>
> static bool is_perf_trbe(struct perf_output_handle *handle)
> @@ -777,12 +785,6 @@ static irqreturn_t arm_trbe_irq_handler(int irq, void *dev)
> if (!is_perf_trbe(handle))
> return IRQ_NONE;
>
> - /*
> - * Ensure perf callbacks have completed, which may disable
> - * the trace buffer in response to a TRUNCATION flag.
> - */
> - irq_work_run();
> -
> act = trbe_get_fault_act(status);
> switch (act) {
> case TRBE_FAULT_ACT_WRAP:
>

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