On Thu, 2009-05-21 at 16:27 -0700, Randy Dunlap wrote:
> Joe Perches wrote:
> > Add a DO_ONCE statement expression analogous to printk_once
> > that executes any arbitrary statement exactly once.
> Since x is of arbitrary size & time duration, I think that x; should follow
> __done = true;
> instead of being before it, as was done in printk_once(). Otherwise there
> could be a sizable window there x could be done more than once.
Makes sense to me.
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>) or any other statement performed
a single time may be easily written.
Signed-off-by: Joe Perches <joe@xxxxxxxxxxx>
---
include/linux/kernel.h | 12 ++++++++++++
1 files changed, 12 insertions(+), 0 deletions(-)
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 883cd44..a5520c9 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -637,7 +637,18 @@ 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 bool __done = false; \
+ \
+ if (!__done) { \
+ __done = true; \
+ 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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