Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752472AbaANC2l (ORCPT ); Mon, 13 Jan 2014 21:28:41 -0500 Received: from numascale.com ([213.162.240.84]:59248 "EHLO numascale.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751682AbaANC2i (ORCPT ); Mon, 13 Jan 2014 21:28:38 -0500 Message-ID: <52D4A0C7.5070601@numascale.com> Date: Tue, 14 Jan 2014 10:28:23 +0800 From: Daniel J Blueman Organization: Numascale AS User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: Waiman Long , Peter Zijlstra CC: "Paul E. McKenney" , Linux Kernel Subject: Re: [PATCH v8 4/4] qrwlock: Use smp_store_release() in write_unlock() References: <52D353C8.4000000@numascale.com> <52D4172E.6030706@hp.com> In-Reply-To: <52D4172E.6030706@hp.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - cpanel21.proisp.no X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - numascale.com X-Get-Message-Sender-Via: cpanel21.proisp.no: authenticated_id: daniel@numascale.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 14/01/2014 00:41, Waiman Long wrote: > On 01/12/2014 09:47 PM, Daniel J Blueman wrote: >> On Thursday, 9 January 2014 01:10:03 UTC+8, Waiman Long wrote: >> > This patch modifies the queue_write_unlock() function to use the >> > new smp_store_release() function in another pending patch. It also >> > removes the temporary implementation of smp_load_acquire() and >> > smp_store_release() function in qrwlock.c. >> > >> > This patch should only be merged if PeterZ's linux-arch patch patch >> > was merged. >> > >> > Signed-off-by: Waiman Long >> > Reviewed-by: Paul E. McKenney >> > --- >> > include/asm-generic/qrwlock.h | 4 +--- >> > kernel/locking/qrwlock.c | 34 >> ---------------------------------- >> > 2 files changed, 1 insertions(+), 37 deletions(-) >> > >> > diff --git a/include/asm-generic/qrwlock.h >> b/include/asm-generic/qrwlock.h >> > index 2b9a7b4..4d4bd04 100644 >> > --- a/include/asm-generic/qrwlock.h >> > +++ b/include/asm-generic/qrwlock.h >> > @@ -179,9 +179,7 @@ static inline void queue_write_unlock(struct >> qrwlock *lock) >> > /* >> > * Make sure that none of the critical section will be leaked out. >> > */ >> > - smp_mb__before_clear_bit(); >> > - ACCESS_ONCE(lock->cnts.writer) = 0; >> > - smp_mb__after_clear_bit(); >> > + smp_store_release(&lock->cnts.writer, 0) >> >> This will fail compilation, so probably needs further testing with >> Peter's load_acquire/store_release barrier patches. >> > > Peter, > > I found out that the build failure was caused by the fact that the > __native_word() macro (used internally by compiletime_assert_atomic()) > allows only a size of 4 or 8 for x86-64. The data type that I used is a > byte. Is there a reason why byte and short are not considered native? It seems likely it was implemented like that since there was no existing need; long can be relied on as the largest native type, so this should suffice and works here: diff --git a/include/linux/compiler.h b/include/linux/compiler.h index fe7a686..dac91d7 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -299,8 +299,8 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect); #endif /* Is this type a native word size -- useful for atomic operations */ -#ifndef __native_word -# define __native_word(t) (sizeof(t) == sizeof(int) || sizeof(t) == sizeof(long)) +#ifndef __native_type +# define __native_type(t) (sizeof(t) <= sizeof(long)) #endif /* Compile time object size, -1 for unknown */ @@ -343,8 +343,8 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect); _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__) #define compiletime_assert_atomic_type(t) \ - compiletime_assert(__native_word(t), \ - "Need native word sized stores/loads for atomicity.") + compiletime_assert(__native_type(t), \ + "Need native sized stores/loads for atomicity.") /* * Prevent the compiler from merging or refetching accesses. The compiler Signed-off-by: Daniel J Blueman -- Daniel J Blueman Principal Software Engineer, Numascale -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/