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authorBoqun Feng <boqun.feng@gmail.com>2015-08-26 19:52:46 +0800
committerIngo Molnar <mingo@kernel.org>2015-09-13 10:35:46 +0200
commit84567995612258c23bc55795575babe7ef605dd9 (patch)
tree69ae01847597ccd3e759b87dc5d11b457839298f /Documentation/atomic_ops.txt
parentc7ef92cea98bc468bbc8e67b6e49d7365dc69482 (diff)
downloadlinux-84567995612258c23bc55795575babe7ef605dd9.tar.bz2
locking/atomics, cmpxchg: Privatize the inclusion of asm/cmpxchg.h
After commit: 654672d4ba1a ("locking/atomics: Add _{acquire|release|relaxed}() variants of some atomic operations") Architectures may only provide {cmp,}xchg_relaxed definitions in asm/cmpxchg.h. Other variants, such as {cmp,}xchg, may be built in linux/atomic.h, which means simply including asm/cmpxchg.h may not get the definitions of all the{cmp,}xchg variants. Therefore, we should privatize the inclusions of asm/cmpxchg.h to keep it only included in arch/* and replace the inclusions outside with linux/atomic.h Signed-off-by: Boqun Feng <boqun.feng@gmail.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Acked-by: Will Deacon <will.deacon@arm.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Aybuke Ozdemir <aybuke.147@gmail.com> Cc: Chris Brannon <chris@the-brannons.com> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Kirk Reiser <kirk@reisers.ca> Cc: Kishon Vijay Abraham I <kishon@ti.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Samuel Thibault <samuel.thibault@ens-lyon.org> Cc: Shradha Shah <sshah@solarflare.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: William Hubbs <w.d.hubbs@gmail.com> Cc: devel@driverdev.osuosl.org Cc: linux-net-drivers@solarflare.com Cc: speakup@linux-speakup.org Link: http://lkml.kernel.org/r/1440589966-26280-1-git-send-email-boqun.feng@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'Documentation/atomic_ops.txt')
-rw-r--r--Documentation/atomic_ops.txt4
1 files changed, 4 insertions, 0 deletions
diff --git a/Documentation/atomic_ops.txt b/Documentation/atomic_ops.txt
index b19fc34efdb1..c9d1cacb4395 100644
--- a/Documentation/atomic_ops.txt
+++ b/Documentation/atomic_ops.txt
@@ -542,6 +542,10 @@ The routines xchg() and cmpxchg() must provide the same exact
memory-barrier semantics as the atomic and bit operations returning
values.
+Note: If someone wants to use xchg(), cmpxchg() and their variants,
+linux/atomic.h should be included rather than asm/cmpxchg.h, unless
+the code is in arch/* and can take care of itself.
+
Spinlocks and rwlocks have memory barrier expectations as well.
The rule to follow is simple: