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The hardware automatically disable the IRQ interrupt before jumping to the interrupt or exception vector. Therefore, the preempt_disable() operation in this_cpu_read() after macro expansion is unnecessary. In fact, function this_cpu_read() may trigger scheduling, see pseudocode below. Pseudocode of this_cpu_read(xx): preempt_disable_notrace(); raw_cpu_read(xx); if (unlikely(__preempt_count_dec_and_test())) __preempt_schedule_notrace(); Therefore, use raw_cpu_* instead of this_cpu_* to eliminate potential hazards. At the very least, it reduces a few lines of assembly code. Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
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.