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From: Christoph Hellwig <hch@infradead.org>
To: Alex Shi <alex.shi@linux.alibaba.com>
Cc: linux-arm-kernel@lists.infradead.org,
	Chris Zankel <chris@zankel.net>, Rich Felker <dalias@libc.org>,
	Yoshinori Sato <ysato@users.sourceforge.jp>,
	David Hildenbrand <david@redhat.com>,
	linux-sh@vger.kernel.org, linux-xtensa@linux-xtensa.org,
	Anshuman Khandual <anshuman.khandual@arm.com>,
	Russell King <linux@armlinux.org.uk>,
	Alexander Duyck <alexander.duyck@gmail.com>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	Max Filippov <jcmvbkbc@gmail.com>,
	Matthew Wilcox <willy@infradead.org>,
	Baolin Wang <baolin.wang@linux.alibaba.com>,
	sparclinux@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
	"David S. Miller" <davem@davemloft.net>,
	Vlastimil Babka <vbabka@suse.cz>
Subject: Re: [PATCH v4 3/4] mm/pageblock: work around multiple arch's cmpxchg support issue
Date: Thu, 10 Sep 2020 05:51:12 +0000	[thread overview]
Message-ID: <20200910055112.GA11727@infradead.org> (raw)
In-Reply-To: <1599116482-7410-3-git-send-email-alex.shi@linux.alibaba.com>

On Thu, Sep 03, 2020 at 03:01:22PM +0800, Alex Shi wrote:
> Armv6, sh2, sparc32 and xtensa can not do cmpxchg1, so we have to use
> cmpxchg4 on it.
> 
> Here we mark above 4 arch's NO_CMPXCHG_BYTE, and would add more if we
> found.
> 
> This is the first usages of cmpxchg flase sharing change. We'd better
> check more cmpxchg usages in current kernel...

I think a positive symbol, e.g. HAVE_CMPXCHG_BYTE is a lot easier to
understand, and also fool-proof.

WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@infradead.org>
To: Alex Shi <alex.shi@linux.alibaba.com>
Cc: linux-arm-kernel@lists.infradead.org,
	Chris Zankel <chris@zankel.net>, Rich Felker <dalias@libc.org>,
	Yoshinori Sato <ysato@users.sourceforge.jp>,
	David Hildenbrand <david@redhat.com>,
	linux-sh@vger.kernel.org, linux-xtensa@linux-xtensa.org,
	Anshuman Khandual <anshuman.khandual@arm.com>,
	Russell King <linux@armlinux.org.uk>,
	Alexander Duyck <alexander.duyck@gmail.com>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	Max Filippov <jcmvbkbc@gmail.com>,
	Matthew Wilcox <willy@infradead.org>,
	Baolin Wang <baolin.wang@linux.alibaba.com>,
	sparclinux@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
	"David S. Miller" <davem@davemloft.net>,
	Vlastimil Babka <vbabka@suse.cz>
Subject: Re: [PATCH v4 3/4] mm/pageblock: work around multiple arch's cmpxchg support issue
Date: Thu, 10 Sep 2020 06:51:12 +0100	[thread overview]
Message-ID: <20200910055112.GA11727@infradead.org> (raw)
In-Reply-To: <1599116482-7410-3-git-send-email-alex.shi@linux.alibaba.com>

On Thu, Sep 03, 2020 at 03:01:22PM +0800, Alex Shi wrote:
> Armv6, sh2, sparc32 and xtensa can not do cmpxchg1, so we have to use
> cmpxchg4 on it.
> 
> Here we mark above 4 arch's NO_CMPXCHG_BYTE, and would add more if we
> found.
> 
> This is the first usages of cmpxchg flase sharing change. We'd better
> check more cmpxchg usages in current kernel...

I think a positive symbol, e.g. HAVE_CMPXCHG_BYTE is a lot easier to
understand, and also fool-proof.

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@infradead.org>
To: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>,
	David Hildenbrand <david@redhat.com>,
	Matthew Wilcox <willy@infradead.org>,
	Vlastimil Babka <vbabka@suse.cz>,
	Alexander Duyck <alexander.duyck@gmail.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Baolin Wang <baolin.wang@linux.alibaba.com>,
	Russell King <linux@armlinux.org.uk>,
	Yoshinori Sato <ysato@users.sourceforge.jp>,
	Rich Felker <dalias@libc.org>,
	"David S. Miller" <davem@davemloft.net>,
	Chris Zankel <chris@zankel.net>,
	Max Filippov <jcmvbkbc@gmail.com>,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, linux-sh@vger.kernel.org,
	sparclinux@vger.kernel.org, linux-xtensa@linux-xtensa.org,
	linux-mm@kvack.org
Subject: Re: [PATCH v4 3/4] mm/pageblock: work around multiple arch's cmpxchg support issue
Date: Thu, 10 Sep 2020 06:51:12 +0100	[thread overview]
Message-ID: <20200910055112.GA11727@infradead.org> (raw)
In-Reply-To: <1599116482-7410-3-git-send-email-alex.shi@linux.alibaba.com>

On Thu, Sep 03, 2020 at 03:01:22PM +0800, Alex Shi wrote:
> Armv6, sh2, sparc32 and xtensa can not do cmpxchg1, so we have to use
> cmpxchg4 on it.
> 
> Here we mark above 4 arch's NO_CMPXCHG_BYTE, and would add more if we
> found.
> 
> This is the first usages of cmpxchg flase sharing change. We'd better
> check more cmpxchg usages in current kernel...

I think a positive symbol, e.g. HAVE_CMPXCHG_BYTE is a lot easier to
understand, and also fool-proof.


  parent reply	other threads:[~2020-09-10  5:51 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-03  7:01 [PATCH v4 1/4] mm/pageblock: mitigation cmpxchg false sharing in pageblock flags Alex Shi
2020-09-03  7:01 ` [PATCH v4 2/4] mm/pageblock: remove false sharing in pageblock_flags Alex Shi
2020-09-03  7:01 ` [PATCH v4 3/4] mm/pageblock: work around multiple arch's cmpxchg support issue Alex Shi
2020-09-03  7:01   ` Alex Shi
2020-09-03  7:01   ` Alex Shi
2020-09-03  7:29   ` Max Filippov
2020-09-03  7:29     ` Max Filippov
2020-09-03  7:29     ` Max Filippov
2020-09-03  8:50     ` Alex Shi
2020-09-03  8:50       ` Alex Shi
2020-09-03  8:50       ` Alex Shi
2020-09-10  5:51   ` Christoph Hellwig [this message]
2020-09-10  5:51     ` Christoph Hellwig
2020-09-10  5:51     ` Christoph Hellwig
2020-09-03  7:24 ` [PATCH v4 1/4] mm/pageblock: mitigation cmpxchg false sharing in pageblock flags Mel Gorman
2020-09-03  8:32   ` Alex Shi
2020-09-03  8:40     ` Alex Shi
2020-09-03  9:00       ` Vlastimil Babka
2020-09-03  9:31     ` Mel Gorman
2020-09-03  8:19 ` David Hildenbrand
2020-09-03  9:14   ` Alex Shi

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