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In some scenarios, user need do some time-consuming or sleepable operations under the hardware spinlock protection for synchronization between the multiple subsystems. For example, there is one PMIC efuse on Spreadtrum platform, which need to be accessed under one hardware lock. But during the hardware lock protection, the efuse operation is time-consuming to almost 5 ms, so we can not disable the interrupts or preemption so long in this case. Thus we can introduce one new mode to indicate that we just acquire the hardware lock and do not disable interrupts or preemption, meanwhile we should force user to protect the hardware lock with mutex or spinlock to avoid dead-lock. Signed-off-by: Baolin Wang <baolin.wang@linaro.org> Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.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.
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.