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wait: explain the shadowing and type inconsistencies

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Stick in a comment before someone else tries to fix the sparse warning
this generates.

Suggested-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
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Peter Zijlstra 2014-04-18 15:07:17 -07:00 committed by Linus Torvalds
parent 9cc236827f
commit 8b32201de1
1 changed files with 13 additions and 1 deletions
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14
include/linux/wait.h
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@ -191,11 +191,23 @@ wait_queue_head_t *bit_waitqueue(void *, int);
(!__builtin_constant_p(state) || \ (!__builtin_constant_p(state) || \
state == TASK_INTERRUPTIBLE || state == TASK_KILLABLE) \ 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) \ #define ___wait_event(wq, condition, state, exclusive, ret, cmd) \
({ \ ({ \
__label__ __out; \ __label__ __out; \
wait_queue_t __wait; \ wait_queue_t __wait; \
long __ret = ret; \ long __ret = ret; /* explicit shadow */ \
\ \
INIT_LIST_HEAD(&__wait.task_list); \ INIT_LIST_HEAD(&__wait.task_list); \
if (exclusive) \ if (exclusive) \