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authorPeter Zijlstra <peterz@infradead.org>2016-05-22 13:48:27 +0300
committerIngo Molnar <mingo@kernel.org>2016-06-08 15:22:47 +0300
commit331b6d8c7afc2e5b900b9dcd850c265e1ba8d8e7 (patch)
treecf3060a9a96357e5f321e5ed28a5165717674f0d /include/linux/compiler.h
parenta461d58792d4a46b8b10ae50973ec9b2763b694e (diff)
downloadlinux-331b6d8c7afc2e5b900b9dcd850c265e1ba8d8e7.tar.xz
locking/barriers: Validate lockless_dereference() is used on a pointer type
Use the type to validate the argument @p is indeed a pointer type. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Paul McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20160522104827.GP3193@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'include/linux/compiler.h')
-rw-r--r--include/linux/compiler.h4
1 files changed, 4 insertions, 0 deletions
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 793c0829e3a3..06f27fd9d760 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -545,10 +545,14 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
* 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 void * variable is to validate @p is indeed a pointer
+ * type. All pointer types silently cast to void *.
*/
#define lockless_dereference(p) \
({ \
typeof(p) _________p1 = READ_ONCE(p); \
+ __maybe_unused const void * const _________p2 = _________p1; \
smp_read_barrier_depends(); /* Dependency order vs. p above. */ \
(_________p1); \
})