From: Waiman Long <waiman.long@hpe.com>
To: Peter Zijlstra <peterz@infradead.org>
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 15:35:47 -0400 [thread overview]
Message-ID: <5761AE13.9040107@hpe.com> (raw)
In-Reply-To: <20160615174508.GU30921@twins.programming.kicks-ass.net>
On 06/15/2016 01:45 PM, Peter Zijlstra wrote:
> 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.
Yes, they are actually the same. I think we could extract the macro
definitions into asm-generic/rwsem-macros.h, for instance, and make the
architecture specific header file include the new generic header.
Cheers,
Longman
next prev parent reply other threads:[~2016-06-15 19:35 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
2016-06-15 19:35 ` Waiman Long [this message]
2016-06-14 22:48 ` [RFC PATCH-tip v2 6/6] locking/rwsem: Enable spinning readers Waiman Long
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