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| author | Peter Zijlstra <peterz@infradead.org> | 2015-05-27 11:09:36 +0930 |
|---|---|---|
| committer | Sasha Levin <sasha.levin@oracle.com> | 2015-09-27 12:18:53 -0400 |
| commit | f23cb735e59b59dce5cd8b2344891d51cc19463f (patch) | |
| tree | 1aff4b534fea8014a5cfab52559519bce20125f9 /include | |
| parent | 057e3a8787b53052e4f5d92a3da6a0b9f5113bea (diff) | |
| download | lwn-f23cb735e59b59dce5cd8b2344891d51cc19463f.tar.gz lwn-f23cb735e59b59dce5cd8b2344891d51cc19463f.zip | |
rcu: Move lockless_dereference() out of rcupdate.h
[ Upstream commit 0a04b0166929405cd833c1cc40f99e862b965ddc ]
I want to use lockless_dereference() from seqlock.h, which would mean
including rcupdate.h from it, however rcupdate.h already includes
seqlock.h.
Avoid this by moving lockless_dereference() into compiler.h. This is
somewhat tricky since it uses smp_read_barrier_depends() which isn't
available there, but its a CPP macro so we can get away with it.
The alternative would be moving it into asm/barrier.h, but that would
be updating each arch (I can do if people feel that is more
appropriate).
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/compiler.h | 15 | ||||
| -rw-r--r-- | include/linux/rcupdate.h | 15 |
2 files changed, 15 insertions, 15 deletions
diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 000c5f90f08c..2bd394ed35f6 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -454,6 +454,21 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s */ #define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(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. + */ +#define lockless_dereference(p) \ +({ \ + typeof(p) _________p1 = ACCESS_ONCE(p); \ + smp_read_barrier_depends(); /* Dependency order vs. p above. */ \ + (_________p1); \ +}) + /* Ignore/forbid kprobes attach on very low level functions marked by this attribute: */ #ifdef CONFIG_KPROBES # define __kprobes __attribute__((__section__(".kprobes.text"))) diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 53ff1a752d7e..a4a819ffb2d1 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -617,21 +617,6 @@ static inline void rcu_preempt_sleep_check(void) #define RCU_INITIALIZER(v) (typeof(*(v)) __force __rcu *)(v) /** - * 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. - */ -#define lockless_dereference(p) \ -({ \ - typeof(p) _________p1 = ACCESS_ONCE(p); \ - smp_read_barrier_depends(); /* Dependency order vs. p above. */ \ - (_________p1); \ -}) - -/** * rcu_assign_pointer() - assign to RCU-protected pointer * @p: pointer to assign to * @v: value to assign (publish) |