Messages in this thread Patch in this message | | | Date | Wed, 9 Apr 2014 13:16:38 +0200 | From | Peter Zijlstra <> | Subject | Re: Regression with wait_event_timeout in next-20140226 |
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On Wed, Feb 26, 2014 at 02:25:34PM -0800, Andrew Morton wrote: > Is there anything we can do to make all this clearer? Simply using a > distinctive variable name ("__wait_var__"?) in place of __ret (and > documenting it) would help a lot. > > Some __ret's are long and some are int. Maybe that's a glitch, maybe > it's because some __ret's are used for inter-macro communications and > some are not, which just makes things worse. > > I started to do a patch, got all confused and gave up. We've made > quite a tangly mess in there, alas.
Something like so?
--- Subject: wait: Explain the shadowing and type inconsistencies From: Peter Zijlstra <peterz@infradead.org> Date: Wed Apr 9 12:50:34 CEST 2014
Stick in a comment before someone else tries to fix the sparse warning this generates.
Requested-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/n/tip-o2ro6f3vkxklni0bc8f7m68s@git.kernel.org --- include/linux/wait.h | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-)
--- a/include/linux/wait.h +++ b/include/linux/wait.h @@ -191,11 +191,23 @@ wait_queue_head_t *bit_waitqueue(void *, (!__builtin_constant_p(state) || \ state == TASK_INTERRUPTIBLE || state == TASK_KILLABLE) \ +/* + * The below macro ___wait_event() has an explicit shadow of the __ret + * variable when used from the wait_event_*() macros. + * + * This is so that both can use the ___wait_cond_timeout() construct + * to wrap the condition. + * + * The type inconsistency of the wait_event_*() __ret variable is also + * on purpose; we use long where we can return timeout values and int + * otherwise. + */ + #define ___wait_event(wq, condition, state, exclusive, ret, cmd) \ ({ \ __label__ __out; \ wait_queue_t __wait; \ - long __ret = ret; \ + long __ret = ret; /* explicit shadow */ \ \ INIT_LIST_HEAD(&__wait.task_list); \ if (exclusive) \
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