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pcc_cpufreq_target(): cpufreq_freq_transition_begin(); spin_lock(&pcc_lock); [critical section] cpufreq_freq_transition_end(); spin_unlock(&pcc_lock); Above code has a performance issue, consider that Task0 executes 'cpufreq_freq_transition_end()' to wake Task1 and preempted imediatedly without releasing 'pcc_lock', then Task1 needs to wait for Task0 to release 'pcc_lock'. In the worst case, this locking order can result in Task1 wasting two scheduling rounds before it can enter the critical section. Signed-off-by: Liao Chang <liaochang1@huawei.com> Acked-by: Viresh Kumar <viresh.kumar@linaro.org> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.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.
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.