linux-kernel - Re: [PATCH] rwsem: fix commas in initialisation

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Date:   Mon, 13 Jul 2020 13:51:41 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Alexey Dobriyan <adobriyan@...il.com>
Cc:     mingo@...hat.com, will@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rwsem: fix commas in initialisation

On Sat, Jul 11, 2020 at 05:59:54PM +0300, Alexey Dobriyan wrote:
> Leading comma prevents arbitrary reordering of initialisation clauses.
> The whole point of C99 initialisation is to allow any such reordering.

I'm conflicted on this argument, the only reason I'd be inclined to take
this patch is that it allows fixing the initialization order to not be
random.

That is, I'd fold in the below.

--- a/include/linux/rwsem.h
+++ b/include/linux/rwsem.h
@@ -89,9 +89,9 @@ static inline int rwsem_is_locked(struct
 #define __RWSEM_INITIALIZER(name)				\
 	{ __RWSEM_INIT_COUNT(name),				\
 	  .owner = ATOMIC_LONG_INIT(0),				\
-	  .wait_list = LIST_HEAD_INIT((name).wait_list),	\
-	  .wait_lock = __RAW_SPIN_LOCK_UNLOCKED(name.wait_lock),\
 	  __RWSEM_OPT_INIT(name)				\
+	  .wait_lock = __RAW_SPIN_LOCK_UNLOCKED(name.wait_lock),\
+	  .wait_list = LIST_HEAD_INIT((name).wait_list),	\
 	  __DEBUG_RWSEM_INITIALIZER(name)			\
 	  __RWSEM_DEP_MAP_INIT(name) }