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From: Keith Packard <keithp@keithp.com>
To: "Russell King (Oracle)" <linux@armlinux.org.uk>
Cc: linux-kernel@vger.kernel.org,
	"Abbott Liu" <liuwenliang@huawei.com>,
	"Alexander Sverdlin" <alexander.sverdlin@gmail.com>,
	"Al Viro" <viro@zeniv.linux.org.uk>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Anshuman Khandual" <anshuman.khandual@arm.com>,
	"Ard Biesheuvel" <ardb@kernel.org>,
	"Arnd Bergmann" <arnd@arndb.de>,
	"Bjorn Andersson" <bjorn.andersson@linaro.org>,
	"Florian Fainelli" <f.fainelli@gmail.com>,
	"Geert Uytterhoeven" <geert+renesas@glider.be>,
	"Hartley Sweeten" <hsweeten@visionengravers.com>,
	"Jens Axboe" <axboe@kernel.dk>, "Jian Cai" <jiancai@google.com>,
	"Joe Perches" <joe@perches.com>,
	"Linus Walleij" <linus.walleij@linaro.org>,
	linux-arm-kernel@lists.infradead.org,
	"Maninder Singh" <maninder1.s@samsung.com>,
	"Manivannan Sadhasivam" <mani@kernel.org>,
	"Marc Zyngier" <maz@kernel.org>,
	"Masahiro Yamada" <masahiroy@kernel.org>,
	"Mike Rapoport" <rppt@kernel.org>,
	"Nick Desaulniers" <ndesaulniers@google.com>,
	"Nick Desaulniers" <ndesaulniers@gooogle.com>,
	"Nicolas Pitre" <nico@fluxnic.net>,
	"Peter Zijlstra" <peterz@infradead.org>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
	"Valentin Schneider" <valentin.schneider@arm.com>,
	"Vaneet Narang" <v.narang@samsung.com>,
	"Wolfram Sang (Renesas)" <wsa+renesas@sang-engineering.com>,
	"YiFei Zhu" <yifeifz2@illinois.edu>
Subject: RE: [PATCH 0/2]: ARM: Enable THREAD_INFO_IN_TASK
Date: Thu, 02 Sep 2021 10:58:32 -0700	[thread overview]
Message-ID: <87a6kuhnav.fsf@keithp.com> (raw)
In-Reply-To: <20210902165353.GI22278@shell.armlinux.org.uk>

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"Russell King (Oracle)" <linux@armlinux.org.uk> writes:

> I think you're introducing a circular dependency with this for
> certain kernel configurations:
>
> E.g. Have you tried running this with CONFIG_CPU_V6 enabled?

That's very useful feedback -- no, I hadn't ever tried this
configuration (presumably the compiler would have complained).

> #define __my_cpu_offset per_cpu_offset(raw_smp_processor_id())

I've read through the v6 architecture reference manual (again) and
cannot find any place to store either a per_cpu_offset or even a small
processor id, which I didn't find surprising as I would have expected it
to already be used for this purpose.

I'll re-spin the changes making them conditional on !CONFIG_CPU_V6,
unless someone has an idea of how to identify the current core in a
multi-core ARMv6 system.

-- 
-keith

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WARNING: multiple messages have this Message-ID (diff)
From: Keith Packard <keithp@keithp.com>
To: "Russell King (Oracle)" <linux@armlinux.org.uk>
Cc: linux-kernel@vger.kernel.org,
	"Abbott Liu" <liuwenliang@huawei.com>,
	"Alexander Sverdlin" <alexander.sverdlin@gmail.com>,
	"Al Viro" <viro@zeniv.linux.org.uk>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Anshuman Khandual" <anshuman.khandual@arm.com>,
	"Ard Biesheuvel" <ardb@kernel.org>,
	"Arnd Bergmann" <arnd@arndb.de>,
	"Bjorn Andersson" <bjorn.andersson@linaro.org>,
	"Florian Fainelli" <f.fainelli@gmail.com>,
	"Geert Uytterhoeven" <geert+renesas@glider.be>,
	"Hartley Sweeten" <hsweeten@visionengravers.com>,
	"Jens Axboe" <axboe@kernel.dk>, "Jian Cai" <jiancai@google.com>,
	"Joe Perches" <joe@perches.com>,
	"Linus Walleij" <linus.walleij@linaro.org>,
	linux-arm-kernel@lists.infradead.org,
	"Maninder Singh" <maninder1.s@samsung.com>,
	"Manivannan Sadhasivam" <mani@kernel.org>,
	"Marc Zyngier" <maz@kernel.org>,
	"Masahiro Yamada" <masahiroy@kernel.org>,
	"Mike Rapoport" <rppt@kernel.org>,
	"Nick Desaulniers" <ndesaulniers@google.com>,
	"Nick Desaulniers" <ndesaulniers@gooogle.com>,
	"Nicolas Pitre" <nico@fluxnic.net>,
	"Peter Zijlstra" <peterz@infradead.org>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
	"Valentin Schneider" <valentin.schneider@arm.com>,
	"Vaneet Narang" <v.narang@samsung.com>,
	"Wolfram Sang (Renesas)" <wsa+renesas@sang-engineering.com>,
	"YiFei Zhu" <yifeifz2@illinois.edu>
Subject: RE: [PATCH 0/2]: ARM: Enable THREAD_INFO_IN_TASK
Date: Thu, 02 Sep 2021 10:58:32 -0700	[thread overview]
Message-ID: <87a6kuhnav.fsf@keithp.com> (raw)
In-Reply-To: <20210902165353.GI22278@shell.armlinux.org.uk>


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"Russell King (Oracle)" <linux@armlinux.org.uk> writes:

> I think you're introducing a circular dependency with this for
> certain kernel configurations:
>
> E.g. Have you tried running this with CONFIG_CPU_V6 enabled?

That's very useful feedback -- no, I hadn't ever tried this
configuration (presumably the compiler would have complained).

> #define __my_cpu_offset per_cpu_offset(raw_smp_processor_id())

I've read through the v6 architecture reference manual (again) and
cannot find any place to store either a per_cpu_offset or even a small
processor id, which I didn't find surprising as I would have expected it
to already be used for this purpose.

I'll re-spin the changes making them conditional on !CONFIG_CPU_V6,
unless someone has an idea of how to identify the current core in a
multi-core ARMv6 system.

-- 
-keith

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  parent reply	other threads:[~2021-09-02 17:58 UTC|newest]

Thread overview: 72+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-02 15:54 [PATCH 0/2]: ARM: Enable THREAD_INFO_IN_TASK Keith Packard
2021-09-02 15:54 ` Keith Packard
2021-09-02 15:54 ` [PATCH 1/2] ARM: Add per-cpu variable holding cpu number Keith Packard
2021-09-02 15:54   ` Keith Packard
2021-09-02 15:54 ` [PATCH 2/2] ARM: Move thread_info into task_struct Keith Packard
2021-09-02 15:54   ` Keith Packard
2021-09-02 16:07 ` [PATCH 0/2]: ARM: Enable THREAD_INFO_IN_TASK Kees Cook
2021-09-02 16:07   ` Kees Cook
2021-09-02 16:18   ` Ard Biesheuvel
2021-09-02 16:18     ` Ard Biesheuvel
2021-09-02 17:37     ` Kees Cook
2021-09-02 17:37       ` Kees Cook
2021-09-02 16:54   ` Russell King (Oracle)
2021-09-02 16:54     ` Russell King (Oracle)
2021-09-02 16:53 ` Russell King (Oracle)
2021-09-02 16:53   ` Russell King (Oracle)
2021-09-02 17:35   ` Kees Cook
2021-09-02 17:35     ` Kees Cook
2021-09-02 17:58   ` Keith Packard [this message]
2021-09-02 17:58     ` Keith Packard
2021-09-04  6:09 ` [PATCH 0/2] ARM: support THREAD_INFO_IN_TASK (v7 only) (v2) Keith Packard
2021-09-04  6:09   ` Keith Packard
2021-09-04  6:09   ` [PATCH 1/3] ARM: Pass cpu number to secondary_start_kernel Keith Packard
2021-09-04  6:09     ` Keith Packard
2021-09-05 20:25     ` Ard Biesheuvel
2021-09-05 20:25       ` Ard Biesheuvel
2021-09-04  6:09   ` [PATCH 2/3] ARM: Move thread_info into task_struct (v7 only) Keith Packard
2021-09-04  6:09     ` Keith Packard
2021-09-05 20:56     ` Ard Biesheuvel
2021-09-05 20:56       ` Ard Biesheuvel
2021-09-06  6:14       ` Keith Packard
2021-09-06  6:14         ` Keith Packard
2021-09-06  7:49         ` Ard Biesheuvel
2021-09-06  7:49           ` Ard Biesheuvel
2021-09-07 15:24           ` Keith Packard
2021-09-07 15:24             ` Keith Packard
2021-09-07 16:05             ` Ard Biesheuvel
2021-09-07 16:05               ` Ard Biesheuvel
2021-09-07 22:17               ` Keith Packard
2021-09-07 22:17                 ` Keith Packard
2021-09-06  6:20       ` Keith Packard
2021-09-06  6:20         ` Keith Packard
2021-09-04  6:09   ` [PATCH 3/3] ARM: Add per-cpu variable cpu_number " Keith Packard
2021-09-04  6:09     ` Keith Packard
2021-09-07 22:00   ` [PATCH 0/7] ARM: support THREAD_INFO_IN_TASK (v3) Keith Packard
2021-09-07 22:00     ` Keith Packard
2021-09-07 22:00     ` [PATCH 1/7] ARM: Pass cpu number to secondary_start_kernel Keith Packard
2021-09-07 22:00       ` Keith Packard
2021-09-07 22:00     ` [PATCH 2/7] ARM: Pass task " Keith Packard
2021-09-07 22:00       ` Keith Packard
2021-09-07 22:00     ` [PATCH 3/7] ARM: Use smp_processor_id() in vfp_pm_suspend instead of ti->cpu Keith Packard
2021-09-07 22:00       ` Keith Packard
2021-09-07 22:00     ` [PATCH 4/7] ARM: Use hack from powerpc to get current cpu number Keith Packard
2021-09-07 22:00       ` Keith Packard
2021-09-08  7:45       ` Ard Biesheuvel
2021-09-08  7:45         ` Ard Biesheuvel
2021-09-07 22:00     ` [PATCH 5/7] ARM: Stop using TPIDRPRW to hold per_cpu_offset Keith Packard
2021-09-07 22:00       ` Keith Packard
2021-09-09 13:54       ` Ard Biesheuvel
2021-09-09 13:54         ` Ard Biesheuvel
2021-09-07 22:00     ` [PATCH 6/7] ARM: Use TPIDRPRW for current Keith Packard
2021-09-07 22:00       ` Keith Packard
2021-09-09 13:56       ` Ard Biesheuvel
2021-09-09 13:56         ` Ard Biesheuvel
2021-09-07 22:00     ` [PATCH 7/7] ARM: Move thread_info into task_struct (v7 only) Keith Packard
2021-09-07 22:00       ` Keith Packard
2021-09-08  7:01     ` [PATCH 0/7] ARM: support THREAD_INFO_IN_TASK (v3) Krzysztof Kozlowski
2021-09-08  7:01       ` Krzysztof Kozlowski
2021-09-08  7:47       ` Ard Biesheuvel
2021-09-08  7:47         ` Ard Biesheuvel
2021-09-08  7:50         ` Geert Uytterhoeven
2021-09-08  7:50           ` Geert Uytterhoeven

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