linux-kernel - Re: [PATCH RFC ticketlock] Auto-queued ticketlock

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Message-ID: <20130610205751.GP5146@linux.vnet.ibm.com>
Date:	Mon, 10 Jun 2013 13:57:51 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, laijs@...fujitsu.com,
	dipankar@...ibm.com, akpm@...ux-foundation.org,
	mathieu.desnoyers@...icios.com, josh@...htriplett.org,
	niv@...ibm.com, tglx@...utronix.de, peterz@...radead.org,
	Valdis.Kletnieks@...edu, dhowells@...hat.com, edumazet@...gle.com,
	darren@...art.com, fweisbec@...il.com, sbw@....edu,
	torvalds@...ux-foundation.org
Subject: Re: [PATCH RFC ticketlock] Auto-queued ticketlock

On Mon, Jun 10, 2013 at 04:47:58PM -0400, Steven Rostedt wrote:
> On Sun, 2013-06-09 at 12:36 -0700, Paul E. McKenney wrote:
> 
> > --- a/arch/x86/include/asm/spinlock_types.h
> > +++ b/arch/x86/include/asm/spinlock_types.h
> > @@ -7,12 +7,18 @@
> >  
> >  #include <linux/types.h>
> >  
> > -#if (CONFIG_NR_CPUS < 256)
> > +#if (CONFIG_NR_CPUS < 128)
> >  typedef u8  __ticket_t;
> >  typedef u16 __ticketpair_t;
> > -#else
> > +#define TICKET_T_CMP_GE(a, b) (UCHAR_MAX / 2 >= (unsigned char)((a) - (b)))
> > +#elif (CONFIG_NR_CPUS < 32768)
> >  typedef u16 __ticket_t;
> >  typedef u32 __ticketpair_t;
> > +#define TICKET_T_CMP_GE(a, b) (USHRT_MAX / 2 >= (unsigned short)((a) - (b)))
> > +#else
> > +typedef u32 __ticket_t;
> > +typedef u64 __ticketpair_t;
> > +#define TICKET_T_CMP_GE(a, b) (UINT_MAX / 2 >= (unsigned int)((a) - (b)))
> >  #endif
> >  
> >  #define TICKET_SHIFT	(sizeof(__ticket_t) * 8)
> > @@ -21,7 +27,11 @@ typedef struct arch_spinlock {
> >  	union {
> >  		__ticketpair_t head_tail;
> >  		struct __raw_tickets {
> > +#ifdef __BIG_ENDIAN__
> 
> Is there such a thing as a BIG_ENDIAN x86 box? This is in
> arch/x86/include/asm/spinlock_types.h

Nope.  Preparation work for moving this to common code.

Good point though, I should have skipped this #ifdef until I got everything
into common code.

							Thanx, Paul

> -- Steve
> 
> > +			__ticket_t tail, head;
> > +#else /* #ifdef __BIG_ENDIAN__ */
> >  			__ticket_t head, tail;
> > +#endif /* #else #ifdef __BIG_ENDIAN__ */
> >  		} tickets;
> >  	};
> >  } arch_spinlock_t;
> 
> 

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