Commit 9c878320 authored Aug 16, 2017 by Steven Rostedt Committed by Ingo Molnar Aug 16, 2017

sched/completion: Document that reinit_completion() must be called after complete_all()



The complete_all() function modifies the completion's "done" variable to
UINT_MAX, and no other caller (wait_for_completion(), etc) will modify
it back to zero. That means that any call to complete_all() must have a
reinit_completion() before that completion can be used again.

Document this fact by the complete_all() function.

Also document that completion_done() will always return true if
complete_all() is called.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170816131202.195c2f4b@gandalf.local.home


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 1e58565e

kernel/sched/completion.c

+8 −0

Original line number	Diff line number	Diff line
		@@ -47,6 +47,13 @@ EXPORT_SYMBOL(complete);
		*
		* It may be assumed that this function implies a write memory barrier before
		* changing the task state if and only if any tasks are woken up.
		*
		* Since complete_all() sets the completion of @x permanently to done
		* to allow multiple waiters to finish, a call to reinit_completion()
		* must be used on @x if @x is to be used again. The code must make
		* sure that all waiters have woken and finished before reinitializing
		* @x. Also note that the function completion_done() can not be used
		* to know if there are still waiters after complete_all() has been called.
		*/
		void complete_all(struct completion *x)
		{
		@@ -297,6 +304,7 @@ EXPORT_SYMBOL(try_wait_for_completion);
		* Return: 0 if there are waiters (wait_for_completion() in progress)
		* 1 if there are no waiters.
		*
		* Note, this will always return true if complete_all() was called on @X.
		*/
		bool completion_done(struct completion *x)
		{