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Some external debuggers do not handle reads/writes from/to DCC on secondary cores. Each core has its own DCC device registers, so when a core reads or writes from/to DCC, it only accesses its own DCC device. Since kernel code can run on any core, every time the kernel wants to write to the console, it might write to a different DCC. In SMP mode, external debugger creates multiple windows, and each window shows the DCC output only from that core's DCC. The result is that console output is either lost or scattered across windows. Selecting this debug option will enable code that serializes all console input and output to core 0. The DCC driver will create input and output FIFOs that all cores will use. Reads and writes from/to DCC are handled by a workqueue that runs only core 0. This is a debug feature to be used only in early stage development where debug serial console support would not be present. It disables PM feature like CPU hotplug and is not suitable for production environment. Signed-off-by: Shanker Donthineni <shankerd@codeaurora.org> Acked-by: Adam Wallis <awallis@codeaurora.org> Signed-off-by: Timur Tabi <timur@codeaurora.org> Signed-off-by: Elliot Berman <eberman@codeaurora.org> Signed-off-by: Sai Prakash Ranjan <quic_saipraka@quicinc.com> Link: https://lore.kernel.org/r/20220428090858.14489-1-quic_saipraka@quicinc.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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.