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1bc92a933f
The "cmd_cache" in RPMH wasn't terribly sensible. Specifically: - The current code doesn't really detect "conflicts" properly any case where the sequence being checked has more than one entry. One simple way to see this in the current code is that if cmd[0].addr isn't found then cmd[1].addr is never checked. - The code attempted to use the "cmd_cache" to update an existing message in a sleep/wake TCS with new data. The goal appeared to be to update part of a TCS while leaving the rest of the TCS alone. We never actually do this. We always fully invalidate and re-write everything. - If/when we try to optimize things to not fully invalidate / re-write every time we update the TCSes we'll need to think it through very carefully. Specifically requirement of find_match() that the new sequence of addrs must match exactly the old sequence of addrs seems inflexible. It's also not documented in rpmh_write() and rpmh_write_batch(). In any case, if we do decide to require updates to keep the exact same sequence and length then presumably the API and data structures should be updated to understand groups more properly. The current algorithm doesn't really keep track of the length of the old sequence and there are several boundary-condition bugs because of that. Said another way: if we decide to do something like this in the future we should start from scratch and thus find_match() isn't useful to keep around. This patch isn't quite a no-op. Specifically: - It should be a slight performance boost of not searching through so many arrays. - The old code would have done something useful in one case: it would allow someone calling rpmh_write() to override the data that came from rpmh_write_batch(). I don't believe that actually happens in reality. Signed-off-by: Douglas Anderson <dianders@chromium.org> Reviewed-by: Maulik Shah <mkshah@codeaurora.org> Reviewed-by: Stephen Boyd <swboyd@chromium.org> Tested-by: Maulik Shah <mkshah@codeaurora.org> Link: https://lore.kernel.org/r/20200413100321.v4.5.I6d3d0a3ec810dc72ff1df3cbf97deefdcdeb8eef@changeid Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org> |
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| README | ||
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.