linux-kernel - Re: [PATCH v2 0/9] coresight: change some driver' spinlock type to raw_spinlock

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Message-ID: <7a370fb3-f5eb-4d6a-a42d-b43960efb930@linaro.org>
Date: Wed, 18 Dec 2024 14:38:07 +0000
From: James Clark <james.clark@...aro.org>
To: Mike Leach <mike.leach@...aro.org>, Yeoreum Yun <yeoreum.yun@....com>
Cc: suzuki.poulose@....com, alexander.shishkin@...ux.intel.com,
 bigeasy@...utronix.de, clrkwllms@...nel.org, rostedt@...dmis.org,
 coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, linux-rt-devel@...ts.linux.dev, nd@....com
Subject: Re: [PATCH v2 0/9] coresight: change some driver' spinlock type to
 raw_spinlock_t



On 18/12/2024 1:44 pm, Mike Leach wrote:
> This change seems to omit devices:
> 
> etm3x - which provides support for ETMv3 and PTM, both of which are
> valid trace sources in the cs_etm handling code.
> stm - can be integrated into the kernel STM via configfs providing a
> MIPI source for ftrace.
> 
> Mike
> 

Isn't ETMv3 32 bit only? arm32 is still missing ARCH_SUPPORTS_RT so we 
could technically leave the spinlocks as is. It might be better to 
update them anyway though or add !PREEMPT_RT to 
CONFIG_CORESIGHT_SOURCE_ETM3X.

> On Tue, 3 Dec 2024 at 11:49, Yeoreum Yun <yeoreum.yun@....com> wrote:
>>
>> In some coresight drivers, drvdata->spinlock can be held during __schedule()
>> by perf_event_task_sched_out()/in().
>>
>> Since drvdata->spinlock type is spinlock_t and
>> perf_event_task_sched_out()/in() is called after acquiring rq_lock,
>> which is raw_spinlock_t (an unsleepable lock),
>> this poses an issue in PREEMPT_RT kernel where spinlock_t is sleepable.
>>
>> To address this,change type drvdata->spinlock in some coresight drivers,
>> which can be called by perf_event_task_sched_out()/in(),
>> from spinlock_t to raw_spinlock_t.
>>
>> Reviewed-by: James Clark <james.clark@...aro.org>
>>
>> v1 to v2:
>>      - seperate patchsets to change locktype and apply gurad API.
>>
>> Levi Yun (9):
>>    coresight: change coresight_device lock type to raw_spinlock_t
>>    coresight-etm4x: change etmv4_drvdata spinlock type to raw_spinlock_t
>>    coresight: change coresight_trace_id_map's lock type to raw_spinlock_t
>>    coresight-cti: change cti_drvdata spinlock's type to raw_spinlock_t
>>    coresight-etb10: change etb_drvdata spinlock's type to raw_spinlock_t
>>    coresight-funnel: change funnel_drvdata spinlock's type to
>>      raw_spinlock_t
>>    coresight-replicator: change replicator_drvdata spinlock's type to
>>      raw_spinlock_t
>>    coresight-tmc: change tmc_drvdata spinlock's type to raw_spinlock_t
>>    coresight/ultrasoc: change cti_drvdata spinlock's type to
>>      raw_spinlock_t
>>
>>   .../hwtracing/coresight/coresight-config.c    |  21 +-
>>   .../hwtracing/coresight/coresight-config.h    |   2 +-
>>   drivers/hwtracing/coresight/coresight-core.c  |   2 +-
>>   .../hwtracing/coresight/coresight-cti-core.c  |  65 +-
>>   .../hwtracing/coresight/coresight-cti-sysfs.c | 135 +++--
>>   drivers/hwtracing/coresight/coresight-cti.h   |   2 +-
>>   drivers/hwtracing/coresight/coresight-etb10.c |  62 +-
>>   .../coresight/coresight-etm4x-core.c          |  71 ++-
>>   .../coresight/coresight-etm4x-sysfs.c         | 566 +++++++++---------
>>   drivers/hwtracing/coresight/coresight-etm4x.h |   2 +-
>>   .../hwtracing/coresight/coresight-funnel.c    |  34 +-
>>   .../coresight/coresight-replicator.c          |  36 +-
>>   .../hwtracing/coresight/coresight-syscfg.c    |  75 ++-
>>   .../hwtracing/coresight/coresight-tmc-core.c  |   9 +-
>>   .../hwtracing/coresight/coresight-tmc-etf.c   | 195 +++---
>>   .../hwtracing/coresight/coresight-tmc-etr.c   | 199 +++---
>>   drivers/hwtracing/coresight/coresight-tmc.h   |   2 +-
>>   .../hwtracing/coresight/coresight-trace-id.c  |  93 ++-
>>   drivers/hwtracing/coresight/ultrasoc-smb.c    |  12 +-
>>   drivers/hwtracing/coresight/ultrasoc-smb.h    |   2 +-
>>   include/linux/coresight.h                     |   4 +-
>>   21 files changed, 751 insertions(+), 838 deletions(-)
>>
>> --
>> LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}
>>
> 
>