Messages in this thread | | | Subject | Re: [PATCH 4/5] coresight: trbe: Move irq_work queue processing | From | Anshuman Khandual <> | Date | Sun, 18 Jul 2021 11:43:49 +0530 |
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On 7/15/21 2:03 PM, Suzuki K Poulose wrote: > On 15/07/2021 04:23, Anshuman Khandual wrote: >> >> >> 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 > > No, it is the other way around. A disable event is triggered > in response to the TRUNCATED flag. > >> disable event be triggered again subsequently ? Just trying to >> understand what is the actual problem because of the current >> placement of irq_work_run() ? > > That begs the question, What is the purpose of irq_work_run() ? > See below. > >> >>> >>> 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. >>> - */ > > This comment here explains what the irq_work_run() is supposed to do. > This clearly indicates that the event will be disabled in response > to TRUNCATION. Now, we haven't updated the buffer flags yet here. > It happens *after* this call, in handle_overflow(). So, this is placed > incorrectly. The purpose of this patch is to make sure that we actually > complete the callbacks in response to the TRUNCATED flag we set with > this IRQ.
Got it.
> >>> - irq_work_run(); >>> - >>> act = trbe_get_fault_act(status); >>> switch (act) { >>> case TRBE_FAULT_ACT_WRAP: >>> > > Suzuki >
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