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locking: Remove ACCESS_ONCE() usage

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With the new standardized functions, we can replace all
ACCESS_ONCE() calls across relevant locking - this includes
lockref and seqlock while at it.

ACCESS_ONCE() does not work reliably on non-scalar types.
For example gcc 4.6 and 4.7 might remove the volatile tag
for such accesses during the SRA (scalar replacement of
aggregates) step:

  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145

Update the new calls regardless of if it is a scalar type,
this is cleaner than having three alternatives.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1424662301.6539.18.camel@stgolabs.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Davidlohr Bueso
2015-02-22 19:31:41 -08:00
committed by Ingo Molnar
parent 2ae7902681
commit 4d3199e4ca
6 changed files with 23 additions and 23 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
kernel/locking/mutex.c
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@@ -266,7 +266,7 @@ static inline int mutex_can_spin_on_owner(struct mutex *lock)
return 0;
rcu_read_lock();
owner = ACCESS_ONCE(lock->owner);
owner = READ_ONCE(lock->owner);
if (owner)
retval = owner->on_cpu;
rcu_read_unlock();
@@ -340,7 +340,7 @@ static bool mutex_optimistic_spin(struct mutex *lock,
* As such, when deadlock detection needs to be
* performed the optimistic spinning cannot be done.
*/
if (ACCESS_ONCE(ww->ctx))
if (READ_ONCE(ww->ctx))
break;
}
@@ -348,7 +348,7 @@ static bool mutex_optimistic_spin(struct mutex *lock,
* If there's an owner, wait for it to either
* release the lock or go to sleep.
*/
owner = ACCESS_ONCE(lock->owner);
owner = READ_ONCE(lock->owner);
if (owner && !mutex_spin_on_owner(lock, owner))
break;
@@ -487,7 +487,7 @@ static inline int __sched
__ww_mutex_lock_check_stamp(struct mutex *lock, struct ww_acquire_ctx *ctx)
{
struct ww_mutex *ww = container_of(lock, struct ww_mutex, base);
struct ww_acquire_ctx *hold_ctx = ACCESS_ONCE(ww->ctx);
struct ww_acquire_ctx *hold_ctx = READ_ONCE(ww->ctx);
if (!hold_ctx)
return 0;