d039f38801
- Plug a race in the lock handoff which is caused by inconsistency of the
reader and writer path and can lead to corruption of the underlying
counter.
- down_read_trylock() is suboptimal when the lock is contended and
multiple readers trylock concurrently. That's due to the initial value
being read non-atomically which results in at least two compare exchange
loops. Making the initial readout atomic reduces this significantly.
Whith 40 readers by 11% in a benchmark which enforces contention on
mmap_sem.
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Merge tag 'locking-urgent-2021-11-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking fixes from Thomas Gleixner:
"Two regression fixes for reader writer semaphores:
- Plug a race in the lock handoff which is caused by inconsistency of
the reader and writer path and can lead to corruption of the
underlying counter.
- down_read_trylock() is suboptimal when the lock is contended and
multiple readers trylock concurrently. That's due to the initial
value being read non-atomically which results in at least two
compare exchange loops. Making the initial readout atomic reduces
this significantly. Whith 40 readers by 11% in a benchmark which
enforces contention on mmap_sem"
* tag 'locking-urgent-2021-11-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
locking/rwsem: Optimize down_read_trylock() under highly contended case
locking/rwsem: Make handoff bit handling more consistent
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| README | ||
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.