[Xen-devel] Re: [PATCH 01/20] x86/ticketlock: clean up types and accessors

[Américo Wang <xiyou.wangcong@xxxxxxxxx>]

On Wed, Nov 03, 2010 at 10:59:42AM -0400, Jeremy Fitzhardinge wrote:
...
> static __always_inline void __ticket_spin_lock(arch_spinlock_t *lock)
> {
>-      int inc = 0x00010000;
>-      int tmp;
>+      unsigned inc = 1 << TICKET_SHIFT;
>+      unsigned tmp;

Please don't use old implicit-int.

> 
>-      return (((tmp >> TICKET_SHIFT) - tmp) & ((1 << TICKET_SHIFT) - 1)) > 1;
>+      return ((tmp.tail - tmp.head) & TICKET_MASK) > 1;


There is a type promotion here.


> }
> 
> #ifndef CONFIG_PARAVIRT_SPINLOCKS
>diff --git a/arch/x86/include/asm/spinlock_types.h 
>b/arch/x86/include/asm/spinlock_types.h
>index dcb48b2..4582640 100644
>--- a/arch/x86/include/asm/spinlock_types.h
>+++ b/arch/x86/include/asm/spinlock_types.h
>@@ -5,11 +5,27 @@
> # error "please don't include this file directly"
> #endif
> 
>+#include <linux/types.h>
>+
>+#if (CONFIG_NR_CPUS < 256)
>+typedef u8  __ticket_t;
>+#else
>+typedef u16 __ticket_t;
>+#endif
>+
>+#define TICKET_SHIFT  (sizeof(__ticket_t) * 8)
>+#define TICKET_MASK   ((1 << TICKET_SHIFT) - 1)


So here you may need to cast the result to __ticket_t.


Thanks.

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