From: Palmer Dabbelt <palmer@rivosinc.com>
Date: Thu, 14 Apr 2022 16:34:29 +0000 (-0700)
Subject: asm-generic: qrwlock: Document the spinlock fairness requirements
X-Git-Tag: v5.19-rc1~89^2~7^2~4
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=493e2ba27635971565a991dc9f689553242890a4;p=thirdparty%2Flinux.git

asm-generic: qrwlock: Document the spinlock fairness requirements

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@arndb.de>
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
---

diff --git a/include/asm-generic/qrwlock.h b/include/asm-generic/qrwlock.h
index 7ae0ece07b4e4..24ae09c1db9f8 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@hp.com>