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In commit95433f7263("srcu: Begin offloading srcu_struct fields to srcu_update"), a new struct srcu_usage field was added, but was not properly initialized. This led to a "spinlock bad magic" BUG when the SRCU notifier was ever used. This was observed in the MediaTek CCI devfreq driver on next-20230525. The trimmed stack trace is as follows: BUG: spinlock bad magic on CPU#4, swapper/0/1 lock: 0xffffff80ff529ac0, .magic: 00000000, .owner: <none>/-1, .owner_cpu: 0 Call trace: spin_bug+0xa4/0xe8 do_raw_spin_lock+0xec/0x120 _raw_spin_lock_irqsave+0x78/0xb8 synchronize_srcu+0x3c/0x168 srcu_notifier_chain_unregister+0x5c/0xa0 cpufreq_unregister_notifier+0x94/0xe0 devfreq_passive_event_handler+0x7c/0x3e0 devfreq_remove_device+0x48/0xe8 Add __SRCU_USAGE_INIT() to SRCU_NOTIFIER_INIT() so that srcu_usage gets initialized properly. Reported-by: Jon Hunter <jonathanh@nvidia.com> Fixes:95433f7263("srcu: Begin offloading srcu_struct fields to srcu_update") Signed-off-by: Chen-Yu Tsai <wenst@chromium.org> Tested-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com> Cc: Matthias Brugger <matthias.bgg@gmail.com> Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com> Cc: "Michał Mirosław" <mirq-linux@rere.qmqm.pl> Cc: Dmitry Osipenko <dmitry.osipenko@collabora.com> Cc: Sachin Sant <sachinp@linux.ibm.com> Cc: Joel Fernandes (Google) <joel@joelfernandes.org Tested-by: Jon Hunter <jonathanh@nvidia.com> Acked-by: Zqiang <qiang.zhang1211@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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.
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.