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Thomas Gleixner 943f0edb75 locking/rt: Add base code for RT rw_semaphore and rwlock
On PREEMPT_RT, rw_semaphores and rwlocks are substituted with an rtmutex and
a reader count. The implementation is writer unfair, as it is not feasible
to do priority inheritance on multiple readers, but experience has shown
that real-time workloads are not the typical workloads which are sensitive
to writer starvation.

The inner workings of rw_semaphores and rwlocks on RT are almost identical
except for the task state and signal handling. rw_semaphores are not state
preserving over a contention, they are expected to enter and leave with state
== TASK_RUNNING. rwlocks have a mechanism to preserve the state of the task
at entry and restore it after unblocking taking potential non-lock related
wakeups into account. rw_semaphores can also be subject to signal handling
interrupting a blocked state, while rwlocks ignore signals.

To avoid code duplication, provide a shared implementation which takes the
small difference vs. state and signals into account. The code is included
into the relevant rw_semaphore/rwlock base code and compiled for each use
case separately.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211302.957920571@linutronix.de
2021-08-17 17:12:22 +02:00
arch powerpc fixes for 5.14 #5 2021-08-15 06:57:43 -10:00
block block-5.14-2021-08-13 2021-08-13 13:36:42 -10:00
certs
crypto
Documentation Linux 5.14-rc6 2021-08-17 16:16:29 +02:00
drivers media/atomisp: Use lockdep instead of *mutex_is_locked() 2021-08-17 16:59:15 +02:00
fs libnvdimm fixes for v5.14-rc6 2021-08-14 19:46:39 -10:00
include locking/rt: Add base code for RT rw_semaphore and rwlock 2021-08-17 17:12:22 +02:00
init
ipc
kernel locking/rt: Add base code for RT rw_semaphore and rwlock 2021-08-17 17:12:22 +02:00
lib lib: use PFN_PHYS() in devmem_is_allowed() 2021-08-13 14:09:32 -10:00
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mm mm/memcg: fix incorrect flushing of lruvec data in obj_stock 2021-08-13 14:09:32 -10:00
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tools libnvdimm fixes for v5.14-rc6 2021-08-14 19:46:39 -10:00
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Makefile Linux 5.14-rc6 2021-08-15 13:40:53 -10:00
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.