Joe Perches wrote:
> 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
> @@ -637,6 +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) { \
> + x; \
> + __done = true; \
Hi Joe,
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.
> + } \
> +})
> +
> /**
> * container_of - cast a member of a structure out to the containing structure
> * @ptr: the pointer to the member.
--
~Randy
LPC 2009, Sept. 23-25, Portland, Oregon
http://linuxplumbersconf.org/2009/
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