wait: explain the shadowing and type inconsistencies

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>

wait: explain the shadowing and type inconsistencies
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>
Peter Zijlstra · Linus Torvalds
1 parent 9cc236827f
Showing 1 changed file with 13 additions and 1 deletions Side-by-side Diff
include/linux/wait.h
@@ -191,11 +191,23 @@
 	(!__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)							\
...	...	@@ -191,11 +191,23 @@
191	191	(!__builtin_constant_p(state) \|\| \
192	192	state == TASK_INTERRUPTIBLE \|\| state == TASK_KILLABLE) \
193	193
	194	+/*
	195	+ * The below macro ___wait_event() has an explicit shadow of the __ret
	196	+ * variable when used from the wait_event_*() macros.
	197	+ *
	198	+ * This is so that both can use the ___wait_cond_timeout() construct
	199	+ * to wrap the condition.
	200	+ *
	201	+ * The type inconsistency of the wait_event_*() __ret variable is also
	202	+ * on purpose; we use long where we can return timeout values and int
	203	+ * otherwise.
	204	+ */
	205	+
194	206	#define ___wait_event(wq, condition, state, exclusive, ret, cmd) \
195	207	({ \
196	208	__label__ __out; \
197	209	wait_queue_t __wait; \
198		- long __ret = ret; \
	210	+ long __ret = ret; /* explicit shadow */ \
199	211	\
200	212	INIT_LIST_HEAD(&__wait.task_list); \
201	213	if (exclusive) \