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The per-CPU resource vmap_block_queue is accessed via get_cpu_var(). That macro disables preemption and then loads the pointer from the current CPU. This doesn't work on PREEMPT_RT because a spinlock_t is later accessed within the preempt-disable section. There is no need to disable preemption while accessing the per-CPU struct vmap_block_queue because the list is protected with a spinlock_t. The per-CPU struct is also accessed cross-CPU in purge_fragmented_blocks(). It is possible that by using raw_cpu_ptr() the code migrates to another CPU and uses struct from another CPU. This is fine because the list is locked and the locked section is very short. Use raw_cpu_ptr() to access vmap_block_queue. Link: https://lkml.kernel.org/r/YnKx3duAB53P7ojN@linutronix.de Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Uladzislau Rezki (Sony) <urezki@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.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.