Manfred Spraul 8116b54e7e ipc/sem.c: document and update memory barriers
Document and update the memory barriers in ipc/sem.c:

- Add smp_store_release() to wake_up_sem_queue_prepare() and
  document why it is needed.

- Read q->status using READ_ONCE+smp_acquire__after_ctrl_dep().
  as the pair for the barrier inside wake_up_sem_queue_prepare().

- Add comments to all barriers, and mention the rules in the block
  regarding locking.

- Switch to using wake_q_add_safe().

Link: http://lkml.kernel.org/r/20191020123305.14715-6-manfred@colorfullife.com
Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Cc: Waiman Long <longman@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: <1vier1@web.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-02-04 03:05:24 +00:00
2020-02-03 16:59:51 +00:00
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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 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.
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