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The cpu hotplug support of this perf driver is broken in several ways: 1) It adds a instance before setting up the state. 2) The state for the instance is different from the state of the callback. It's just a randomly chosen state. 3) The instance registration is not error checked so nobody noticed that the call can never succeed. 4) The state for the multi install callbacks is chosen randomly and overwrites existing state. This is now prevented by the core code so the call is guaranteed to fail. 5) The error exit path in the init function leaves the instance registered and then frees the memory which contains the enqueued hlist node. 6) The remove function is removing the state and not the instance. Fix it by: - Setting up the state before adding instances. Use a dynamically allocated state for it. - Installing instances after the state has been set up - Removing the instance in the error path before freeing memory - Removing the instance not the state in the driver remove callback While at is use raw_cpu_processor_id(), because cpu_processor_id() cannot be used in preemptible context, and set the driver data after successful registration of the pmu. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Shawn Guo <shawnguo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Siewior <bigeasy@linutronix.de> Cc: Frank Li <frank.li@nxp.com> Cc: Zhengyu Shen <zhengyu.shen@nxp.com> Link: http://lkml.kernel.org/r/20161221192111.596204211@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. 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.