Re: [PATCH 0/9] coresight: change some driver' spinlock type to raw_spinlock_t

From: James Clark
Date: Wed Nov 27 2024 - 11:45:57 EST




On 25/11/2024 9:48 am, Yeoreum Yun 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.

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(-)

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LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}


Reviewed-by: James Clark <james.clark@xxxxxxxxxx>

Somewhat related to this change, but not something that needs to be done now:

All of the spinlocks for the syfs store/read functions don't need to be raw spinlocks, or spinlocks at all. They're never called from the scheduling code and can be locked by coresight_mutex instead. coresight_mutex is held on the sysfs enable/disable path when those values are actually used.

Same point as here: https://lore.kernel.org/linux-arm-kernel/9a637e74-d81d-405c-bad0-c97ec1aa4b77@xxxxxxxxxx/

Probably needs a review of which values in each device might be shared between perf mode and sysfs mode when they shouldn't be, as there was one in the link above.

I thought the only thing shared between sysfs and perf should be the 'mode' which is taken with a compare and swap without locking anyway.