From: Jamie Lokier <jamie@shareable.org>
To: Li Li <eggonlea@gmail.com>
Cc: Tony Lindgren <tony@atomide.com>,
linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
Nicolas Pitre <nico@fluxnic.net>
Subject: Re: [PATCH 1/2] arm: Replace CONFIG_HAS_TLS_REG with HWCAP_TLS and check for it on V6
Date: Fri, 8 Apr 2011 15:35:41 +0100 [thread overview]
Message-ID: <20110408143541.GU26912@shareable.org> (raw)
In-Reply-To: <BANLkTinEnn1C8_mKtL6P2YXdPSt1eaUzKA@mail.gmail.com>
Li Li wrote:
> Nicolas,
>
> Thanks for the explanation. :)
>
> I noticed what you mentioned. Actually, Kconfig says TLS EMU might be
> used in some "old" (e.g. pre-armv6) SMP platforms without TLS
> register. In such a case, could we still ensure it's SMP safe by a
> single ldr?
In that case, the hardware TLS 'mcr' is used, which traps and is
emulated by the undefined instruction handler. It's not fast but
presumably those platforms don't really matter.
See CONFIG_TLS_REG_EMUL in arch/arm/kernel/traps.c, and 'tls_emu'.
'tls_emu' is a constant, so if a kernel built for TLS emulation is run
on something which has the TLS register, it will not work properly.
-- JAmie
WARNING: multiple messages have this Message-ID (diff)
From: jamie@shareable.org (Jamie Lokier)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 1/2] arm: Replace CONFIG_HAS_TLS_REG with HWCAP_TLS and check for it on V6
Date: Fri, 8 Apr 2011 15:35:41 +0100 [thread overview]
Message-ID: <20110408143541.GU26912@shareable.org> (raw)
In-Reply-To: <BANLkTinEnn1C8_mKtL6P2YXdPSt1eaUzKA@mail.gmail.com>
Li Li wrote:
> Nicolas,
>
> Thanks for the explanation. :)
>
> I noticed what you mentioned. Actually, Kconfig says TLS EMU might be
> used in some "old" (e.g. pre-armv6) SMP platforms without TLS
> register. In such a case, could we still ensure it's SMP safe by a
> single ldr?
In that case, the hardware TLS 'mcr' is used, which traps and is
emulated by the undefined instruction handler. It's not fast but
presumably those platforms don't really matter.
See CONFIG_TLS_REG_EMUL in arch/arm/kernel/traps.c, and 'tls_emu'.
'tls_emu' is a constant, so if a kernel built for TLS emulation is run
on something which has the TLS register, it will not work properly.
-- JAmie
next prev parent reply other threads:[~2011-04-08 14:35 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-21 13:51 [PATCH 0/2] Make ARMv6 behave with TLS, VFPv3, and NEON Tony Lindgren
2010-06-21 13:51 ` Tony Lindgren
2010-06-21 13:51 ` [PATCH 1/2] arm: Replace CONFIG_HAS_TLS_REG with HWCAP_TLS and check for it on V6 Tony Lindgren
2010-06-21 13:51 ` Tony Lindgren
2010-06-22 9:28 ` Tony Lindgren
2010-06-22 9:28 ` Tony Lindgren
2010-06-22 17:00 ` Jamie Lokier
2010-06-22 17:00 ` Jamie Lokier
2010-06-23 7:39 ` Tony Lindgren
2010-06-23 7:39 ` Tony Lindgren
2010-06-23 8:12 ` Russell King - ARM Linux
2010-06-23 8:12 ` Russell King - ARM Linux
2010-06-23 9:28 ` Tony Lindgren
2010-06-23 9:28 ` Tony Lindgren
2010-06-23 9:32 ` Russell King - ARM Linux
2010-06-23 9:32 ` Russell King - ARM Linux
2010-06-23 13:28 ` Jamie Lokier
2010-06-23 13:28 ` Jamie Lokier
2010-06-23 13:36 ` Jamie Lokier
2010-06-23 13:36 ` Jamie Lokier
2010-06-23 14:19 ` Nicolas Pitre
2010-06-23 14:19 ` Nicolas Pitre
2010-06-24 0:28 ` Jamie Lokier
2010-06-24 0:28 ` Jamie Lokier
2010-06-29 14:18 ` Tony Lindgren
2010-06-29 14:18 ` Tony Lindgren
2010-06-29 19:20 ` Nicolas Pitre
2010-06-29 19:20 ` Nicolas Pitre
2010-06-30 11:08 ` Tony Lindgren
2010-06-30 11:08 ` Tony Lindgren
2010-06-30 13:17 ` Tony Lindgren
2010-06-30 13:17 ` Tony Lindgren
2010-06-30 14:42 ` Nicolas Pitre
2010-06-30 14:42 ` Nicolas Pitre
2010-07-01 9:25 ` Tony Lindgren
2010-07-01 9:25 ` Tony Lindgren
2010-07-01 17:40 ` Jamie Lokier
2010-07-01 17:40 ` Jamie Lokier
2010-07-02 2:37 ` Nicolas Pitre
2010-07-02 2:37 ` Nicolas Pitre
2010-07-02 10:37 ` Tony Lindgren
2010-07-02 10:37 ` Tony Lindgren
2010-07-05 13:55 ` Tony Lindgren
2010-07-05 13:55 ` Tony Lindgren
2011-04-08 3:39 ` Li Li
2011-04-08 3:39 ` Li Li
2011-04-08 13:19 ` Nicolas Pitre
2011-04-08 13:19 ` Nicolas Pitre
2011-04-08 13:35 ` Li Li
2011-04-08 13:35 ` Li Li
2011-04-08 14:35 ` Jamie Lokier [this message]
2011-04-08 14:35 ` Jamie Lokier
2011-04-08 14:40 ` Li Li
2011-04-08 14:40 ` Li Li
2010-06-21 13:51 ` [PATCH 2/2] arm: Make VFPv3 usable on ARMv6 Tony Lindgren
2010-06-21 13:51 ` Tony Lindgren
2010-06-22 12:59 ` Catalin Marinas
2010-06-22 12:59 ` Catalin Marinas
2010-06-22 13:20 ` Tony Lindgren
2010-06-22 13:20 ` Tony Lindgren
2010-06-23 7:57 ` Tony Lindgren
2010-06-23 7:57 ` Tony Lindgren
2010-06-25 13:50 ` Catalin Marinas
2010-06-25 13:50 ` Catalin Marinas
2010-07-01 12:42 ` Tony Lindgren
2010-07-01 12:42 ` Tony Lindgren
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