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locking/qspinlock: Fix inaccessible URL of MCS lock paper 

It turns out that the URL of the MCS lock paper listed in the source
code is no longer accessible. I did got question about where the paper
was. This patch updates the URL to BZ 206115 which contains a copy of
the paper from

  https://www.cs.rochester.edu/u/scott/papers/1991_TOCS_synch.pdf

Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lkml.kernel.org/r/20200107174914.4187-1-longman@redhat.com
This commit is contained in:
Waiman Long 2020-01-07 12:49:14 -05:00 committed by Peter Zijlstra
parent a030f9767d
commit 57097124cb
1 changed files with 7 additions and 6 deletions
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13
kernel/locking/qspinlock.c
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@ -31,14 +31,15 @@
/*
* The basic principle of a queue-based spinlock can best be understood
* by studying a classic queue-based spinlock implementation called the
* MCS lock. The paper below provides a good description for this kind
* of lock.
* MCS lock. A copy of the original MCS lock paper ("Algorithms for Scalable
* Synchronization on Shared-Memory Multiprocessors by Mellor-Crummey and
* Scott") is available at
*
* http://www.cise.ufl.edu/tr/DOC/REP-1992-71.pdf
* https://bugzilla.kernel.org/show_bug.cgi?id=206115
*
* This queued spinlock implementation is based on the MCS lock, however to make
* it fit the 4 bytes we assume spinlock_t to be, and preserve its existing
* API, we must modify it somehow.
* This queued spinlock implementation is based on the MCS lock, however to
* make it fit the 4 bytes we assume spinlock_t to be, and preserve its
* existing API, we must modify it somehow.
*
* In particular; where the traditional MCS lock consists of a tail pointer
* (8 bytes) and needs the next pointer (another 8 bytes) of its own node to