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authorSteven Rostedt <rostedt@goodmis.org>2017-08-16 13:12:02 -0400
committerIngo Molnar <mingo@kernel.org>2017-08-16 20:08:10 +0200
commit9c8783201cb58e9af8ddeb0cc68f37b0a44ca16c (patch)
tree212c0a154e726ca945bc890886a1190e60568c31 /kernel/sched
parent1e58565e6d147751d85ee9e692d1226059b3318f (diff)
downloadlinux-9c8783201cb58e9af8ddeb0cc68f37b0a44ca16c.tar.bz2
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>
Diffstat (limited to 'kernel/sched')
-rw-r--r--kernel/sched/completion.c8
1 files changed, 8 insertions, 0 deletions
diff --git a/kernel/sched/completion.c b/kernel/sched/completion.c
index 13fc5ae9bf2f..2950f446820d 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)
{