Re: [PATCHv6 1/3] xen: use ticket locks for spin locks

[David Vrabel <david.vrabel@citrix.com>]

On 18/05/15 11:16, Jan Beulich wrote:
>>>> On 14.05.15 at 13:21, <david.vrabel@citrix.com> wrote:
>>  void _spin_lock(spinlock_t *lock)
>>  {
>> +    spinlock_tickets_t tickets = { .tail = 1, };
> 
> This breaks the build on gcc 4.3.x (due to tail being a member of an
> unnamed structure member of a union).

I don't have a gcc that old to hand but isn't the error here that .tail
is part of the structure that isn't the first member of a union?

Does this fix your gcc 4.3 build?

--- a/xen/include/xen/spinlock.h
+++ b/xen/include/xen/spinlock.h
@@ -115,7 +115,7 @@ extern void spinlock_profile_reset(unsigned char key);

 struct lock_profile_qhead { };

-#define SPIN_LOCK_UNLOCKED { { 0 }, 0xfffu, 0, _LOCK_DEBUG }
+#define SPIN_LOCK_UNLOCKED { {}, 0xfffu, 0, _LOCK_DEBUG }
 #define DEFINE_SPINLOCK(l) spinlock_t l = SPIN_LOCK_UNLOCKED

 #define spin_lock_init_prof(s, l) spin_lock_init(&((s)->l))
@@ -125,11 +125,11 @@ struct lock_profile_qhead { };
 #endif

 typedef union {
-    u32 head_tail;
     struct {
         u16 head;
         u16 tail;
     };
+    u32 head_tail;
 } spinlock_tickets_t;

 typedef struct spinlock {