[PATCH v5 3/7] asm-generic: qrwlock: Document the spinlock fairness requirements

[Palmer Dabbelt]

From: Palmer Dabbelt <palmer at rivosinc.com>

I could only find the fairness requirements documented as the C code,
this calls them out in a comment just to be a bit more explicit.

Reviewed-by: Arnd Bergmann <arnd at arndb.de
Signed-off-by: Palmer Dabbelt <palmer at rivosinc.com>
---
 include/asm-generic/qrwlock.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/include/asm-generic/qrwlock.h b/include/asm-generic/qrwlock.h
index 7ae0ece07b4e..24ae09c1db9f 100644
--- a/include/asm-generic/qrwlock.h
+++ b/include/asm-generic/qrwlock.h
@@ -2,6 +2,10 @@
 /*
  * Queue read/write lock
  *
+ * These use generic atomic and locking routines, but depend on a fair spinlock
+ * implementation in order to be fair themselves.  The implementation in
+ * asm-generic/spinlock.h meets these requirements.
+ *
  * (C) Copyright 2013-2014 Hewlett-Packard Development Company, L.P.
  *
  * Authors: Waiman Long <waiman.long at hp.com>
-- 
2.34.1