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From: Peter Zijlstra <peterz@infradead.org>
To: Waiman Long <Waiman.Long@hpe.com>
Cc: Ingo Molnar <mingo@redhat.com>,
	linux-kernel@vger.kernel.org, x86@kernel.org,
	linux-alpha@vger.kernel.org, linux-ia64@vger.kernel.org,
	linux-s390@vger.kernel.org, linux-arch@vger.kernel.org,
	Davidlohr Bueso <dave@stgolabs.net>,
	Jason Low <jason.low2@hp.com>, Dave Chinner <david@fromorbit.com>,
	Scott J Norton <scott.norton@hpe.com>,
	Douglas Hatch <doug.hatch@hpe.com>
Subject: Re: [RFC PATCH-tip v2 5/6] locking/rwsem: Change RWSEM_WAITING_BIAS for better disambiguation
Date: Wed, 15 Jun 2016 19:45:08 +0200	[thread overview]
Message-ID: <20160615174508.GU30921@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <1465944489-43440-6-git-send-email-Waiman.Long@hpe.com>

On Tue, Jun 14, 2016 at 06:48:08PM -0400, Waiman Long wrote:
> +++ b/arch/alpha/include/asm/rwsem.h
> @@ -17,9 +17,9 @@
>  #define RWSEM_UNLOCKED_VALUE		0x0000000000000000L
>  #define RWSEM_ACTIVE_BIAS		0x0000000000000001L
>  #define RWSEM_ACTIVE_MASK		0x00000000ffffffffL
> -#define RWSEM_WAITING_BIAS		(-0x0000000100000000L)
> +#define RWSEM_WAITING_BIAS		0xc000000000000000L
>  #define RWSEM_ACTIVE_READ_BIAS		RWSEM_ACTIVE_BIAS
> -#define RWSEM_ACTIVE_WRITE_BIAS		(RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
> +#define RWSEM_ACTIVE_WRITE_BIAS		(-RWSEM_ACTIVE_MASK)

> +++ b/arch/ia64/include/asm/rwsem.h
> @@ -30,9 +30,9 @@
>  #define RWSEM_UNLOCKED_VALUE		__IA64_UL_CONST(0x0000000000000000)
>  #define RWSEM_ACTIVE_BIAS		(1L)
>  #define RWSEM_ACTIVE_MASK		(0xffffffffL)
> -#define RWSEM_WAITING_BIAS		(-0x100000000L)
> +#define RWSEM_WAITING_BIAS		(-(1L << 62))
>  #define RWSEM_ACTIVE_READ_BIAS		RWSEM_ACTIVE_BIAS
> -#define RWSEM_ACTIVE_WRITE_BIAS		(RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
> +#define RWSEM_ACTIVE_WRITE_BIAS		(-RWSEM_ACTIVE_MASK)

> +++ b/arch/s390/include/asm/rwsem.h
> @@ -42,9 +42,9 @@
>  #define RWSEM_UNLOCKED_VALUE	0x0000000000000000L
>  #define RWSEM_ACTIVE_BIAS	0x0000000000000001L
>  #define RWSEM_ACTIVE_MASK	0x00000000ffffffffL
> -#define RWSEM_WAITING_BIAS	(-0x0000000100000000L)
> +#define RWSEM_WAITING_BIAS	0xc000000000000000L
>  #define RWSEM_ACTIVE_READ_BIAS	RWSEM_ACTIVE_BIAS
> -#define RWSEM_ACTIVE_WRITE_BIAS	(RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
> +#define RWSEM_ACTIVE_WRITE_BIAS	(-RWSEM_ACTIVE_MASK)

> +++ b/arch/x86/include/asm/rwsem.h
> @@ -41,21 +41,23 @@
>  
>  /*
>   * The bias values and the counter type limits the number of
> - * potential readers/writers to 32767 for 32 bits and 2147483647
> - * for 64 bits.
> + * potential writers to 16383 for 32 bits and 1073741823 for 64 bits.
> + * The combined readers and writers can go up to 65534 for 32-bits and
> + * 4294967294 for 64-bits.
>   */
>  
>  #ifdef CONFIG_X86_64
>  # define RWSEM_ACTIVE_MASK		0xffffffffL
> +# define RWSEM_WAITING_BIAS		(-(1L << 62))
>  #else
>  # define RWSEM_ACTIVE_MASK		0x0000ffffL
> +# define RWSEM_WAITING_BIAS		(-(1L << 30))
>  #endif
>  
>  #define RWSEM_UNLOCKED_VALUE		0x00000000L
>  #define RWSEM_ACTIVE_BIAS		0x00000001L
> -#define RWSEM_WAITING_BIAS		(-RWSEM_ACTIVE_MASK-1)
>  #define RWSEM_ACTIVE_READ_BIAS		RWSEM_ACTIVE_BIAS
> -#define RWSEM_ACTIVE_WRITE_BIAS		(RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
> +#define RWSEM_ACTIVE_WRITE_BIAS		(-RWSEM_ACTIVE_MASK)

> +++ b/include/asm-generic/rwsem.h
> @@ -18,15 +18,16 @@
>   */
>  #ifdef CONFIG_64BIT
>  # define RWSEM_ACTIVE_MASK		0xffffffffL
> +# define RWSEM_WAITING_BIAS		(-(1L << 62))
>  #else
>  # define RWSEM_ACTIVE_MASK		0x0000ffffL
> +# define RWSEM_WAITING_BIAS		(-(1L << 30))
>  #endif
>  
>  #define RWSEM_UNLOCKED_VALUE		0x00000000L
>  #define RWSEM_ACTIVE_BIAS		0x00000001L
> -#define RWSEM_WAITING_BIAS		(-RWSEM_ACTIVE_MASK-1)
>  #define RWSEM_ACTIVE_READ_BIAS		RWSEM_ACTIVE_BIAS
> -#define RWSEM_ACTIVE_WRITE_BIAS		(RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
> +#define RWSEM_ACTIVE_WRITE_BIAS		(-RWSEM_ACTIVE_MASK)

Can't we collapse all that? They all seem very similar.

  parent reply	other threads:[~2016-06-15 17:45 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-14 22:48 [RFC PATCH-tip v2 0/6] locking/rwsem: Enable reader optimistic spinning Waiman Long
2016-06-14 22:48 ` [RFC PATCH-tip v2 1/6] locking/osq: Make lock/unlock proper acquire/release barrier Waiman Long
2016-06-15  8:04   ` Boqun Feng
2016-06-15 17:18     ` Peter Zijlstra
2016-06-15 19:01     ` Waiman Long
2016-06-16  2:19       ` Boqun Feng
2016-06-16 10:16         ` Will Deacon
2016-06-16 21:35         ` Waiman Long
2016-06-17  0:48           ` Boqun Feng
2016-06-17 15:26             ` Waiman Long
2016-06-17 15:45               ` Will Deacon
2016-06-17 18:17                 ` Waiman Long
2016-06-18  8:46                   ` Boqun Feng
2016-06-20  7:59                     ` Will Deacon
2016-06-15 16:56   ` Davidlohr Bueso
2016-06-15 17:12     ` Peter Zijlstra
2016-06-15 18:27       ` Davidlohr Bueso
2016-06-15 18:40         ` Peter Zijlstra
2016-06-15 18:56           ` Davidlohr Bueso
2016-06-17  1:11           ` Davidlohr Bueso
2016-06-17 14:28             ` Waiman Long
2016-06-17 16:29               ` Davidlohr Bueso
2016-06-17 16:46                 ` Davidlohr Bueso
2016-06-15 19:08       ` Waiman Long
2016-06-15 20:04         ` Waiman Long
2016-06-15 21:59           ` Peter Zijlstra
2016-06-14 22:48 ` [RFC PATCH-tip v2 2/6] locking/rwsem: Stop active read lock ASAP Waiman Long
2016-06-15 17:22   ` Peter Zijlstra
2016-06-15 19:17     ` Waiman Long
2016-06-16  2:14       ` Davidlohr Bueso
2016-06-16 21:25         ` Waiman Long
2016-06-14 22:48 ` [RFC PATCH-tip v2 3/6] locking/rwsem: Enable count-based spinning on reader Waiman Long
2016-06-15 17:38   ` Peter Zijlstra
2016-06-15 19:28     ` Waiman Long
2016-06-14 22:48 ` [RFC PATCH-tip v2 4/6] locking/rwsem: move down rwsem_down_read_failed function Waiman Long
2016-06-15 17:40   ` Peter Zijlstra
2016-06-15 19:21     ` Waiman Long
2016-06-14 22:48 ` [RFC PATCH-tip v2 5/6] locking/rwsem: Change RWSEM_WAITING_BIAS for better disambiguation Waiman Long
2016-06-15 17:43   ` Peter Zijlstra
2016-06-15 19:31     ` Waiman Long
2016-06-15 21:57       ` Peter Zijlstra
2016-06-15 17:45   ` Peter Zijlstra [this message]
2016-06-15 19:35     ` Waiman Long
2016-06-14 22:48 ` [RFC PATCH-tip v2 6/6] locking/rwsem: Enable spinning readers Waiman Long

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