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Currently poll_timeout_us() evaluates 'op' and 'cond' twice within the loop, once at the start, and a second time after the timeout check. While it's probably not a big deal to do it twice almost back to back, it does make the macro a bit messy. Simplify the implementation to evaluate the timeout at the very start, then follow up with 'op'/'cond', and finally check if the timeout did in fact happen or not. For good measure throw in a compiler barrier between the timeout and 'op'/'cond' evaluations to make sure the compiler can't reoder the operations (which could cause false positive timeouts). The similar i915 __wait_for() macro already has the barrier, though there it is between the 'op' and 'cond' evaluations, which seems like it could still allow 'op' and the timeout evaluations to get reordered incorrectly. I suppose the ktime_get() might itself act as a sufficient barrier here, but better safe than sorry I guess. Cc: Lucas De Marchi <lucas.demarchi@intel.com> Cc: Dibin Moolakadan Subrahmanian <dibin.moolakadan.subrahmanian@intel.com> Cc: Imre Deak <imre.deak@intel.com> Cc: David Laight <david.laight.linux@gmail.com> Cc: Geert Uytterhoeven <geert+renesas@glider.be> Cc: Matt Wagantall <mattw@codeaurora.org> Cc: Dejin Zheng <zhengdejin5@gmail.com> Cc: intel-gfx@lists.freedesktop.org Cc: intel-xe@lists.freedesktop.org Cc: linux-kernel@vger.kernel.org Reviewed-by: Jani Nikula <jani.nikula@intel.com> Acked-by: Simona Vetter <simona.vetter@ffwll.ch> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com> Link: https://lore.kernel.org/r/20250826121859.15497-3-ville.syrjala@linux.intel.com Signed-off-by: Jani Nikula <jani.nikula@intel.com> |
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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 reStructuredText 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.