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Subject[PATCH V2 1/3] kernel.h: Add DO_ONCE statement expression macro
Date
Add a DO_ONCE statement expression analogous to printk_once
that executes any arbitrary statement exactly once.

This will take the place of printk_once so that
DO_ONCE(pr_<foo>) can be more easily written.

Signed-off-by: Joe Perches <joe@perches.com>
---
include/linux/kernel.h | 11 +++++++++++
1 files changed, 11 insertions(+), 0 deletions(-)
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 883cd44..179fdac 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -637,6 +637,17 @@ static inline void ftrace_dump(void) { }
#define swap(a, b) \
do { typeof(a) __tmp = (a); (a) = (b); (b) = __tmp; } while (0)

+/*
+ * Do something once (analogous to WARN_ONCE() et al):
+ */
+#define DO_ONCE(x...) ({ \
+ static unsigned long __done; \
+ \
+ if (!test_and_set_bit(0, &__done)) { \
+ x; \
+ } \
+})
+
/**
* container_of - cast a member of a structure out to the containing structure
* @ptr: the pointer to the member.
--
1.6.3.1.10.g659a0.dirty


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