Commit-ID: 9c8783201cb58e9af8ddeb0cc68f37b0a44ca16c Gitweb: http://git.kernel.org/tip/9c8783201cb58e9af8ddeb0cc68f37b0a44ca16c Author: Steven Rostedt <rost...@goodmis.org> AuthorDate: Wed, 16 Aug 2017 13:12:02 -0400 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Wed, 16 Aug 2017 20:08:10 +0200
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) <rost...@goodmis.org> Acked-by: Linus Torvalds <torva...@linux-foundation.org> Cc: Andrew Morton <a...@linux-foundation.org> Cc: Paul E. McKenney <paul...@linux.vnet.ibm.com> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Thomas Gleixner <t...@linutronix.de> Link: http://lkml.kernel.org/r/20170816131202.195c2...@gandalf.local.home Signed-off-by: Ingo Molnar <mi...@kernel.org> --- kernel/sched/completion.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/kernel/sched/completion.c b/kernel/sched/completion.c index 13fc5ae..2950f44 100644 --- a/kernel/sched/completion.c +++ b/kernel/sched/completion.c @@ -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) {
