diff options
| author |   Will Deacon <will.deacon@arm.com> | 2017-10-24 11:22:49 +0100 |
|---|---|---|
| committer |   Ingo Molnar <mingo@kernel.org> | 2017-10-24 13:17:33 +0200 |
| commit | 59ecbbe7b31cd2d86ff9a9f461a00f7e7533aedc (patch) | |
| tree | cb293c6c7810f9d781bb6f0c4017b2b3dd8a27bb /include/linux/compiler.h | |
| parent | locking/barriers: Convert users of lockless_dereference() to READ_ONCE() (diff) | |
| download | linux-dev-59ecbbe7b31cd2d86ff9a9f461a00f7e7533aedc.tar.xz linux-dev-59ecbbe7b31cd2d86ff9a9f461a00f7e7533aedc.zip | |
locking/barriers: Kill lockless_dereference()
lockless_dereference() is a nice idea, but it gained little traction in
kernel code since its introduction three years ago. This is partly
because it's a pain to type, but also because using READ_ONCE() instead
has worked correctly on all architectures apart from Alpha, which is a
fully supported but somewhat niche architecture these days.
Now that READ_ONCE() has been upgraded to contain an implicit
smp_read_barrier_depends() and the few callers of lockless_dereference()
have been converted, we can remove lockless_dereference() altogether.
Signed-off-by: Will Deacon <will.deacon@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1508840570-22169-5-git-send-email-will.deacon@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'include/linux/compiler.h')
| -rw-r--r-- | include/linux/compiler.h | 20 |
1 files changed, 0 insertions, 20 deletions
diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 7d7b77da9716..5a1cab48442c 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -346,24 +346,4 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s (volatile typeof(x) *)&(x); }) #define ACCESS_ONCE(x) (*__ACCESS_ONCE(x)) -/** - * lockless_dereference() - safely load a pointer for later dereference - * @p: The pointer to load - * - * Similar to rcu_dereference(), but for situations where the pointed-to - * object's lifetime is managed by something other than RCU. That - * "something other" might be reference counting or simple immortality. - * - * The seemingly unused variable ___typecheck_p validates that @p is - * indeed a pointer type by using a pointer to typeof(*p) as the type. - * Taking a pointer to typeof(*p) again is needed in case p is void *. - */ -#define lockless_dereference(p) \ -({ \ - typeof(p) _________p1 = READ_ONCE(p); \ - typeof(*(p)) *___typecheck_p __maybe_unused; \ - smp_read_barrier_depends(); /* Dependency order vs. p above. */ \ - (_________p1); \ -}) - #endif /* __LINUX_COMPILER_H */ |