linux-kernel - Re: [PATCH v3 0/9] coresight: change some driver' spinlock type to raw_spinlock

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Message-ID: <CAJ9a7VhxG_8R6j5uRCzOhLpy4ZmzyVvyW0+ryCcd4w7wqpZ2ew@mail.gmail.com>
Date: Thu, 19 Dec 2024 12:27:47 +0000
From: Mike Leach <mike.leach@...aro.org>
To: Yeoreum Yun <yeoreum.yun@....com>
Cc: suzuki.poulose@....com, james.clark@...aro.org, 
	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
Subject: Re: [PATCH v3 0/9] coresight: change some driver' spinlock type to raw_spinlock_t

Hi,

On Mon, 16 Dec 2024 at 11:50, 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>
>
> v2 to v3:
>     - Fix build error
>
> v1 to v2:
>     - seperate patchsets to change locktype and apply gurad API.
>
> Yeoreum 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    |   8 +-
>  .../hwtracing/coresight/coresight-config.h    |   2 +-
>  drivers/hwtracing/coresight/coresight-core.c  |   2 +-
>  .../hwtracing/coresight/coresight-cti-core.c  |  44 +--
>  .../hwtracing/coresight/coresight-cti-sysfs.c |  76 +++---
>  drivers/hwtracing/coresight/coresight-cti.h   |   2 +-
>  drivers/hwtracing/coresight/coresight-etb10.c |  26 +-
>  .../coresight/coresight-etm4x-core.c          |  18 +-
>  .../coresight/coresight-etm4x-sysfs.c         | 250 +++++++++---------
>  drivers/hwtracing/coresight/coresight-etm4x.h |   2 +-
>  .../hwtracing/coresight/coresight-funnel.c    |  12 +-
>  .../coresight/coresight-replicator.c          |  12 +-
>  .../hwtracing/coresight/coresight-syscfg.c    |  26 +-
>  .../hwtracing/coresight/coresight-tmc-core.c  |   6 +-
>  .../hwtracing/coresight/coresight-tmc-etf.c   |  48 ++--
>  .../hwtracing/coresight/coresight-tmc-etr.c   |  40 +--
>  drivers/hwtracing/coresight/coresight-tmc.h   |   2 +-
>  .../hwtracing/coresight/coresight-trace-id.c  |  22 +-
>  drivers/hwtracing/coresight/ultrasoc-smb.c    |  12 +-
>  drivers/hwtracing/coresight/ultrasoc-smb.h    |   2 +-
>  include/linux/coresight.h                     |   4 +-
>  21 files changed, 308 insertions(+), 308 deletions(-)
>
> --
> LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}
>

Notably missing is the same changes for the etm3x driver. The ETMv3.x
and PTM1.x are supported by this driver, and these trace source
variants are also supported in perf in the cs_etm.c code.

STM is also missing, though this is not directly enabled via perf -
but could perhaps run concurrently as it can be a target output for
ftrace.

Regards

Mike

-- 
Mike Leach
Principal Engineer, ARM Ltd.
Manchester Design Centre. UK