linux-kernel - [PATCH v2 0/9] coresight: Fix CTI module refcount leak by making it a helper device

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Date:   Fri, 10 Mar 2023 16:05:59 +0000
From:   James Clark <james.clark@....com>
To:     coresight@...ts.linaro.org
Cc:     James Clark <james.clark@....com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach <mike.leach@...aro.org>,
        Leo Yan <leo.yan@...aro.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 0/9] coresight: Fix CTI module refcount leak by making it a helper device

Changes since v1:

 * Don't dereference handle in tmc_etr_get_buffer() when not in perf mode.
 * Fix some W=1 warnings
 * Add a commit to rename child/output in terms of local/remote

-------------------

Currently there is a refcount leak in CTI when using system wide mode
or tracing multithreaded applications. See the last commit for a
reproducer. This prevents the module from being unloaded.

Historically there have been a few issues and fixes attempted around
here which have resulted in some extra logic and a member to keep
track of CTI being enabled 'struct coresight_device->ect_enabled'.
The fix in commit 665c157e0204 ("coresight: cti: Fix hang in
cti_disable_hw()") was also related to CTI having its own
enable/disable path which came later than other devices.

If we make CTI a helper device and enable helper devices adjacent to
the path we get very similar enable/disable behavior to now, but with
more reuse of the existing reference counting logic in the coresight
core code. This also affects CATU which can have a little bit of
its hard coded enable/disable code removed.

Enabling CATU on the generic path does require that input connections
are tracked so that it can get its associated ETR buffer.

Applies to coresight/next (669c4614236a7) but also requires the
realloc_array patch here [1].

Also available in full here [2].

[1]: https://lore.kernel.org/linux-arm-kernel/20230306152723.3090195-1-james.clark@arm.com/
[2]: https://gitlab.arm.com/linux-arm/linux-jc/-/tree/james-cs-cti-module-refcount-fix-v2

James Clark (9):
  coresight: Use enum type for cs_mode wherever possible
  coresight: Change name of pdata->conns
  coresight: Rename nr_outports to nr_outconns
  coresight: Rename connection members to allow for input connections
  coresight: Dynamically add connections
  coresight: Store in-connections as well as out-connections
  coresight: Refactor out buffer allocation function for ETR
  coresight: Enable and disable helper devices adjacent to the path
  coresight: Fix CTI module refcount leak by making it a helper device

 drivers/hwtracing/coresight/coresight-catu.c  |  34 +-
 drivers/hwtracing/coresight/coresight-core.c  | 312 +++++++++++-------
 .../hwtracing/coresight/coresight-cti-core.c  |  56 ++--
 .../hwtracing/coresight/coresight-cti-sysfs.c |   4 +-
 drivers/hwtracing/coresight/coresight-cti.h   |   4 +-
 drivers/hwtracing/coresight/coresight-etb10.c |   3 +-
 .../coresight/coresight-etm3x-core.c          |   6 +-
 .../coresight/coresight-etm4x-core.c          |   6 +-
 .../hwtracing/coresight/coresight-platform.c  | 178 +++++++---
 drivers/hwtracing/coresight/coresight-priv.h  |   9 +-
 drivers/hwtracing/coresight/coresight-stm.c   |   6 +-
 drivers/hwtracing/coresight/coresight-sysfs.c |   9 +-
 .../hwtracing/coresight/coresight-tmc-etf.c   |   2 +-
 .../hwtracing/coresight/coresight-tmc-etr.c   |  89 ++---
 drivers/hwtracing/coresight/coresight-tmc.h   |   2 +
 drivers/hwtracing/coresight/coresight-tpdm.c  |   4 +-
 drivers/hwtracing/coresight/coresight-tpiu.c  |   3 +-
 drivers/hwtracing/coresight/coresight-trbe.c  |   3 +-
 drivers/hwtracing/coresight/ultrasoc-smb.c    |   3 +-
 drivers/hwtracing/coresight/ultrasoc-smb.h    |   2 +-
 include/linux/coresight.h                     | 109 +++---
 21 files changed, 530 insertions(+), 314 deletions(-)

-- 
2.34.1