Messages in this thread | | | Subject | Re: [PATCH 4/5] coresight: trbe: Move irq_work queue processing | From | Suzuki K Poulose <> | Date | Thu, 15 Jul 2021 09:33:49 +0100 |
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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.
>> - irq_work_run(); >> - >> act = trbe_get_fault_act(status); >> switch (act) { >> case TRBE_FAULT_ACT_WRAP: >>
Suzuki
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