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From: Nathan Chancellor <natechancellor@gmail.com>
To: Will Deacon <will@kernel.org>
Cc: mark.rutland@arm.com, peterz@infradead.org,
	catalin.marinas@arm.com, ndesaulniers@google.com,
	Ard.Biesheuvel@arm.com, andrew.murray@arm.com,
	robin.murphy@arm.com, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v5 03/10] arm64: atomics: avoid out-of-line ll/sc atomics
Date: Mon, 2 Sep 2019 23:00:11 -0700	[thread overview]
Message-ID: <20190903060011.GA60737@archlinux-threadripper> (raw)
In-Reply-To: <20190829154834.26547-4-will@kernel.org>

On Thu, Aug 29, 2019 at 04:48:27PM +0100, Will Deacon wrote:
> From: Andrew Murray <andrew.murray@arm.com>
> 
> When building for LSE atomics (CONFIG_ARM64_LSE_ATOMICS), if the hardware
> or toolchain doesn't support it the existing code will fallback to ll/sc
> atomics. It achieves this by branching from inline assembly to a function
> that is built with special compile flags. Further this results in the
> clobbering of registers even when the fallback isn't used increasing
> register pressure.
> 
> Improve this by providing inline implementations of both LSE and
> ll/sc and use a static key to select between them, which allows for the
> compiler to generate better atomics code. Put the LL/SC fallback atomics
> in their own subsection to improve icache performance.
> 
> Signed-off-by: Andrew Murray <andrew.murray@arm.com>
> Signed-off-by: Will Deacon <will@kernel.org>

For some reason, this causes a clang built kernel to fail to boot in
QEMU. There are no logs, it just never starts. I am off for the next two
days so I am going to try to look into this but you might have some
immediate ideas.

https://github.com/ClangBuiltLinux/linux/issues/649

There is another weird failure that might be somewhat related but I have
no idea.

https://github.com/ClangBuiltLinux/linux/issues/648

Cheers,
Nathan

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  reply	other threads:[~2019-09-03  6:01 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-29 15:48 [PATCH v5 00/10] arm64: avoid out-of-line ll/sc atomics Will Deacon
2019-08-29 15:48 ` [PATCH v5 01/10] jump_label: Don't warn on __exit jump entries Will Deacon
2019-08-29 15:48 ` [PATCH v5 02/10] arm64: Use correct ll/sc atomic constraints Will Deacon
2019-08-29 15:48 ` [PATCH v5 03/10] arm64: atomics: avoid out-of-line ll/sc atomics Will Deacon
2019-09-03  6:00   ` Nathan Chancellor [this message]
2019-09-03  6:39     ` Will Deacon
2019-09-03 14:31     ` Andrew Murray
2019-09-03 14:45       ` Will Deacon
2019-09-03 15:15         ` Andrew Murray
2019-09-03 15:31           ` Andrew Murray
2019-09-03 16:37             ` Will Deacon
2019-09-03 22:04               ` Andrew Murray
2019-09-03 22:35                 ` Nick Desaulniers
     [not found]                   ` <CANW9uyuRFtNKMnSwmHWt_RebJA1ADXdZfeDHc6=yaaFH2NsyWg@mail.gmail.com>
2019-09-03 22:53                     ` Nick Desaulniers
2019-09-04 10:20                       ` Will Deacon
2019-09-04 17:28                 ` Nick Desaulniers
2019-09-05 11:25                   ` Andrew Murray
2019-09-06 19:44                     ` Nick Desaulniers
2019-08-29 15:48 ` [PATCH v5 04/10] arm64: avoid using hard-coded registers for LSE atomics Will Deacon
2019-08-29 15:48 ` [PATCH v5 05/10] arm64: atomics: Remove atomic_ll_sc compilation unit Will Deacon
2019-08-29 17:47   ` Nick Desaulniers
2019-08-29 20:07     ` Tri Vo
2019-08-29 21:54       ` Will Deacon
2019-08-29 15:48 ` [PATCH v5 06/10] arm64: lse: Remove unused 'alt_lse' assembly macro Will Deacon
2019-08-29 23:39   ` Andrew Murray
2019-08-29 15:48 ` [PATCH v5 07/10] arm64: asm: Kill 'asm/atomic_arch.h' Will Deacon
2019-08-29 23:43   ` Andrew Murray
2019-08-29 15:48 ` [PATCH v5 08/10] arm64: lse: Make ARM64_LSE_ATOMICS depend on JUMP_LABEL Will Deacon
2019-08-29 23:44   ` Andrew Murray
2019-08-29 15:48 ` [PATCH v5 09/10] arm64: atomics: Undefine internal macros after use Will Deacon
2019-08-29 23:44   ` Andrew Murray
2019-08-29 15:48 ` [PATCH v5 10/10] arm64: atomics: Use K constraint when toolchain appears to support it Will Deacon
2019-08-29 16:54   ` Will Deacon
2019-08-29 17:45     ` Nick Desaulniers
2019-08-29 21:53       ` Will Deacon
2019-08-30 20:57         ` Nick Desaulniers
2019-08-30  0:08     ` Andrew Murray
2019-08-30  7:52       ` Will Deacon
2019-08-30  9:11         ` Andrew Murray
2019-08-30 10:17           ` Will Deacon
2019-08-30 11:57             ` Andrew Murray
2019-08-30 10:40           ` Mark Rutland
2019-08-30 11:53             ` Andrew Murray
2019-08-29 23:49   ` Andrew Murray

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