linux-kernel - [tip:locking/urgent] locking/qspinlock: Fix build for anonymous union in older GCC compilers

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Date:   Thu, 21 Jun 2018 19:24:49 -0700
From:   "tip-bot for Steven Rostedt (VMware)" <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     tglx@...utronix.de, will.deacon@....com, rostedt@...dmis.org,
        akpm@...ux-foundation.org, longman@...hat.com,
        linux-kernel@...r.kernel.org, boqun.feng@...il.com,
        peterz@...radead.org, torvalds@...ux-foundation.org,
        mingo@...nel.org, hpa@...or.com
Subject: [tip:locking/urgent] locking/qspinlock: Fix build for anonymous
 union in older GCC compilers

Commit-ID:  6cc65be4f6f2a7186af8f3e09900787c7912dad2
Gitweb:     https://git.kernel.org/tip/6cc65be4f6f2a7186af8f3e09900787c7912dad2
Author:     Steven Rostedt (VMware) <rostedt@...dmis.org>
AuthorDate: Thu, 21 Jun 2018 20:35:26 -0400
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Fri, 22 Jun 2018 04:19:16 +0200

locking/qspinlock: Fix build for anonymous union in older GCC compilers

One of my tests compiles the kernel with gcc 4.5.3, and I hit the
following build error:

  include/linux/semaphore.h: In function 'sema_init':
  include/linux/semaphore.h:35:17: error: unknown field 'val' specified in initializer
  include/linux/semaphore.h:35:17: warning: missing braces around initializer
  include/linux/semaphore.h:35:17: warning: (near initialization for '(anonymous).raw_lock.<anonymous>.val')

I bisected it down to:

 625e88be1f41 ("locking/qspinlock: Merge 'struct __qspinlock' into 'struct qspinlock'")

... which makes qspinlock have an anonymous union, which makes initializing it special
for older compilers. By adding strategic brackets, it makes the build
happy again.

Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
Acked-by: Waiman Long <longman@...hat.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Boqun Feng <boqun.feng@...il.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Will Deacon <will.deacon@....com>
Cc: linux-arm-kernel@...ts.infradead.org
Fixes: 625e88be1f41 ("locking/qspinlock: Merge 'struct __qspinlock' into 'struct qspinlock'")
Link: http://lkml.kernel.org/r/20180621203526.172ab5c4@vmware.local.home
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 include/asm-generic/qspinlock_types.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/asm-generic/qspinlock_types.h b/include/asm-generic/qspinlock_types.h
index 0763f065b975..d10f1e7d6ba8 100644
--- a/include/asm-generic/qspinlock_types.h
+++ b/include/asm-generic/qspinlock_types.h
@@ -63,7 +63,7 @@ typedef struct qspinlock {
 /*
  * Initializier
  */
-#define	__ARCH_SPIN_LOCK_UNLOCKED	{ .val = ATOMIC_INIT(0) }
+#define	__ARCH_SPIN_LOCK_UNLOCKED	{ { .val = ATOMIC_INIT(0) } }
 
 /*
  * Bitfields in the atomic value: