[PATCH 1/1] docs/memory-barriers.txt: Add wait_event_cmd() and wait_event_exclusive_cmd()

Add said functions to the documentation and relate them to userspace's
pthread_cond_wait(). The latter because when searching for
functionality comparable to pthread_cond_wait(), it is very hard to
find wait_event_cmd().

Signed-off-by: Håkon Bugge <[email protected]>
---
 Documentation/memory-barriers.txt | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt
index 93d58d9a428b8..d721e9be5a4f5 100644
--- a/Documentation/memory-barriers.txt
+++ b/Documentation/memory-barriers.txt
@@ -2192,6 +2192,8 @@ interpolate the memory barrier in the right place:
 	wait_event_timeout();
 	wait_on_bit();
 	wait_on_bit_lock();
+	wait_event_cmd();
+	wait_event_exclusive_cmd();
 
 
 Secondly, code that performs a wake up normally follows something like this:
@@ -2296,6 +2298,15 @@ and the waker should do:
 	event_indicated = 1;
 	wake_up(&event_wait_queue);
 
+Note that the wait_event_cmd() and wait_event_exclusive_cmd() are the
+kernel's polymorphic implementation of userspace's
+pthread_cond_wait().
+
+Using wait_event_cmd() or wait_event_exclusive_cmd(), cmd1 is
+typically a lock-release call and cmd2 a lock-acquire call. The
+locking primitive can be chosen, contrary to pthread_cond_wait(),
+where the locking type is cast in stone and is a pthread_mutex_t.
+
 
 MISCELLANEOUS FUNCTIONS
 -----------------------
-- 
2.43.5