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Section 2.1 of the Platform Specification [1] states:
Unless otherwise specified by a given I/O device, I/O devices are on
ordering channel 0 (i.e., they are point-to-point strongly ordered).
which is not sufficient to guarantee that a readX() by a hart completes
before a subsequent delay() on the same hart (cf. memory-barriers.txt,
"Kernel I/O barrier effects").
Set the I(nput) bit in __io_ar() to restore the ordering, align inline
comments.
[1] https://github.com/riscv/riscv-platform-specs
Signed-off-by: Andrea Parri <parri.andrea@gmail.com>
Link: https://lore.kernel.org/r/20230803042738.5937-1-parri.andrea@gmail.com
Fixes: fab957c11e ("RISC-V: Atomic and Locking Code")
Cc: stable@vger.kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.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.