| Message ID | 20210712113830.2803257-5-suzuki.poulose@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | coresight: TRBE and Self-Hosted trace fixes | expand |
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: >
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
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 >
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:
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. 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(-)