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Backport: coresight-dynamic-replicator.c and coresight-replicator.c has been merged upstream into coresight-replicator.c, in commit455328b177. So backport the change to both of the files. When tracing etm data of multiple threads on multiple cpus through perf interface, some link devices are shared between paths of different cpus. It creates race conditions when different cpus wants to enable/disable the same link device at the same time. Example 1: Two cpus want to enable different ports of a coresight funnel, thus calling the funnel enable operation at the same time. But the funnel enable operation isn't reentrantable. Example 2: For an enabled coresight dynamic replicator with refcnt=1, one cpu wants to disable it, while another cpu wants to enable it. Ideally we still have an enabled replicator with refcnt=1 at the end. But in reality the result is uncertain. Since coresight devices claim themselves when enabled for self-hosted usage, the race conditions above usually make the link devices not usable after many cycles. To fix the race conditions, this patch uses spinlocks to serialize enabling/disabling link devices. Fixes:a06ae8609b("coresight: add CoreSight core layer framework") Signed-off-by: Yabin Cui <yabinc@google.com> Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org> Cc: stable <stable@vger.kernel.org> # 5.3 Link: https://lore.kernel.org/r/20191104181251.26732-14-mathieu.poirier@linaro.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> (cherry picked from commitedda32dabegit://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git char-misc-next) Bug: 140266694 Change-Id: I59a1a36c3e4771a57910f6f437fd2ce5f3cfab6e Signed-off-by: Yabin Cui <yabinc@google.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.