Commit 6d5f0ebf authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull core locking updates from Ingo Molnar:
 "The main updates in this cycle were:

   - mutex MCS refactoring finishing touches: improve comments, refactor
     and clean up code, reduce debug data structure footprint, etc.

   - qrwlock finishing touches: remove old code, self-test updates.

   - small rwsem optimization

   - various smaller fixes/cleanups"

* 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  locking/lockdep: Revert qrwlock recusive stuff
  locking/rwsem: Avoid double checking before try acquiring write lock
  locking/rwsem: Move EXPORT_SYMBOL() lines to follow function definition
  locking/rwlock, x86: Delete unused asm/rwlock.h and rwlock.S
  locking/rwlock, x86: Clean up asm/spinlock*.h to remove old rwlock code
  locking/semaphore: Resolve some shadow warnings
  locking/selftest: Support queued rwlock
  locking/lockdep: Restrict the use of recursive read_lock() with qrwlock
  locking/spinlocks: Always evaluate the second argument of spin_lock_nested()
  locking/Documentation: Update locking/mutex-design.txt disadvantages
  locking/Documentation: Move locking related docs into Documentation/locking/
  locking/mutexes: Use MUTEX_SPIN_ON_OWNER when appropriate
  locking/mutexes: Refactor optimistic spinning code
  locking/mcs: Remove obsolete comment
  locking/mutexes: Document quick lock release when unlocking
  locking/mutexes: Standardize arguments in lock/unlock slowpaths
  locking: Remove deprecated smp_mb__() barriers
parents dbb885fe 8acd91e8

Documentation/00-INDEX

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@@ -287,6 +287,8 @@ local_ops.txt 
	- semantics and behavior of local atomic operations.

lockdep-design.txt

	- documentation on the runtime locking correctness validator.

locking/

	- directory with info about kernel locking primitives

lockstat.txt

	- info on collecting statistics on locks (and contention).

lockup-watchdogs.txt

Documentation/DocBook/kernel-locking.tmpl

+1 −1
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@@ -1972,7 +1972,7 @@ machines due to caching. 
   <itemizedlist>

    <listitem>

     <para>

       <filename>Documentation/spinlocks.txt</filename>: 

       <filename>Documentation/locking/spinlocks.txt</filename>:

       Linus Torvalds' spinlocking tutorial in the kernel sources.

     </para>

    </listitem>

Documentation/lockstat.txt→Documentation/locking/lockstat.txt

+1 −1
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@@ -12,7 +12,7 @@ Because things like lock contention can severely impact performance. 
- HOW



Lockdep already has hooks in the lock functions and maps lock instances to

lock classes. We build on that (see Documentation/lockdep-design.txt).

lock classes. We build on that (see Documentation/lokcing/lockdep-design.txt).

The graph below shows the relation between the lock functions and the various

hooks therein.

Documentation/mutex-design.txt→Documentation/locking/mutex-design.txt

+3 −3
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@@ -145,9 +145,9 @@ Disadvantages 


Unlike its original design and purpose, 'struct mutex' is larger than

most locks in the kernel. E.g: on x86-64 it is 40 bytes, almost twice

as large as 'struct semaphore' (24 bytes) and 8 bytes shy of the

'struct rw_semaphore' variant. Larger structure sizes mean more CPU

cache and memory footprint.

as large as 'struct semaphore' (24 bytes) and tied, along with rwsems,

for the largest lock in the kernel. Larger structure sizes mean more

CPU cache and memory footprint.



When to use mutexes

-------------------

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