On Fri, Feb 20, 2015 at 11:31:53AM -0800, Eric Dumazet wrote:
> On Fri, 2015-02-20 at 19:58 +0100, Peter Zijlstra wrote:
> Maybe this might be self documented in set_current_state(),
> as we have about 120 calls to __set_current_state(TASK_RUNNING)
>
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index 41c60e5302d7..26133da6445e 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -275,7 +275,11 @@ extern char ___assert_task_state[1 - 2*!!(
> #define set_current_state(state_value) \
> do { \
> current->task_state_change = _THIS_IP_; \
> - set_mb(current->state, (state_value)); \
> + if (__builtin_constant_p(state_value) && \
> + (state_value) == TASK_RUNNING) \
> + current->state = (state_value); \
> + else \
> + set_mb(current->state, (state_value)); \
> } while (0)
lkml.kernel.org/r/20150206163947.gr21...@twins.programming.kicks-ass.net
The problem is that there _might_ be someone relying on that barrier.
Its (very) unlikely, but you don't want to risk subtle borkage just
because. And I'm too lazy to go audit all of them :/
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