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From: Peter Zijlstra <peterz@infradead.org>
To: Stefan Asserhall <stefana@xilinx.com>
Cc: Michal Simek <michals@xilinx.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"monstr@monstr.eu" <monstr@monstr.eu>, git <git@xilinx.com>,
	"arnd@arndb.de" <arnd@arndb.de>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Masahiro Yamada <yamada.masahiro@socionext.com>,
	Will Deacon <will@kernel.org>
Subject: Re: [PATCH 3/7] microblaze: Define SMP safe bit operations
Date: Thu, 13 Feb 2020 10:11:01 +0100	[thread overview]
Message-ID: <20200213091101.GM14897@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <BYAPR02MB499729CFF3B9FD7DDDCFBCD8DD1A0@BYAPR02MB4997.namprd02.prod.outlook.com>

On Thu, Feb 13, 2020 at 09:01:21AM +0000, Stefan Asserhall wrote:
> The comment in the generic bitops.h says "You should recode these in the
> native assembly language, if at all possible". I don't think using the generic
> implementation will be as efficient as the current arch specific one.

That is a very crusty old recommendation. Please look at the compiler
generated code.

We've extended the atomic_t operations the past few years and Will wrote
the generic atomic bitops for Arm64, we're looking to convert more LL/SC
archs to them.

There is currently one known issue with it, but Will has a patch-set
pending to solve that (IIRC that only matters if you have stack
protector on).

Also see this thread:

  https://lkml.kernel.org/r/875zimp0ay.fsf@mpe.ellerman.id.au

And these patches:

  https://lkml.kernel.org/r/20200123153341.19947-1-will@kernel.org

  reply	other threads:[~2020-02-13  9:11 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-12 15:42 [PATCH 0/7] microblaze: Define SMP safe operations Michal Simek
2020-02-12 15:42 ` [PATCH 1/7] microblaze: timer: Don't use cpu timer setting Michal Simek
2020-02-12 15:42 ` [PATCH 2/7] microblaze: Make cpuinfo structure SMP aware Michal Simek
2020-02-12 20:42   ` Arnd Bergmann
2020-02-12 15:42 ` [PATCH 3/7] microblaze: Define SMP safe bit operations Michal Simek
2020-02-12 15:53   ` Peter Zijlstra
2020-02-13  8:42     ` Michal Simek
2020-02-13  9:01       ` Stefan Asserhall
2020-02-13  9:11         ` Peter Zijlstra [this message]
2020-02-13  9:24           ` Stefan Asserhall
2020-02-12 15:42 ` [PATCH 4/7] microblaze: Add SMP implementation of xchg and cmpxchg Michal Simek
2020-02-12 15:42 ` [PATCH 5/7] microblaze: Remove disabling IRQ while pte_update() run Michal Simek
2020-02-12 15:42 ` [PATCH 6/7] microblaze: Implement architecture spinlock Michal Simek
2020-02-12 15:47   ` Peter Zijlstra
2020-02-13  7:51     ` Michal Simek
2020-02-13  8:00       ` Peter Zijlstra
2020-02-12 15:42 ` [PATCH 7/7] microblaze: Do atomic operations by using exclusive ops Michal Simek
2020-02-12 15:55   ` Peter Zijlstra
2020-02-13  8:06     ` Michal Simek
2020-02-13  8:58       ` Peter Zijlstra
2020-02-13  9:16         ` Peter Zijlstra
2020-02-13 10:04           ` Will Deacon
2020-02-13 10:14             ` Stefan Asserhall
2020-02-13 10:20               ` Will Deacon
2020-02-13 10:15             ` Peter Zijlstra
2020-02-13 11:34         ` Boqun Feng
2020-02-13 11:38           ` Boqun Feng
2020-02-13 13:51             ` Andrea Parri
2020-02-13 14:01               ` Andrea Parri
2020-02-12 16:08 ` [PATCH 0/7] microblaze: Define SMP safe operations Peter Zijlstra
2020-02-12 16:38   ` Peter Zijlstra
2020-02-13  7:49   ` Michal Simek
2020-02-13  8:11     ` Peter Zijlstra
2020-02-13  8:12       ` Michal Simek

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