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9aaf9bb794
Currently ARCH_HAVE_NMI_SAFE_CMPXCHG is not set on Arm systems and this makes it impossible to enable features such as ftrace histogram triggers on Arm platforms. Most Arm systems are NMI safe simply because there is no NMI but this isn't universally true meaning we cannot set ARCH_HAVE_NMI_SAFE_CMPXCHG for all Arm devices. However the load/store exclusive implementation of cmpxchg is NMI-safe and this implementation is used ARMv6k and later. Let's select ARCH_HAVE_NMI_SAFE_CMPXCHG for these systems. Note that ARMv6 uses load/store exclusive for 32-bit cmpxchg but relies on interrupt masking for 8- and 16-bit operations. This patch is conservative and does not change behaviour for CPU_V6. Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org> Signed-off-by: Russell King <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.