From: Stephen Boyd <sboyd@codeaurora.org>
To: Timur Tabi <timur@tabi.org>
Cc: Arpit Goel <B44344@freescale.com>,
linux@arm.linux.org.uk, takata@linux-m32r.org, philb@gnu.org,
Geert Uytterhoeven <geert@linux-m68k.org>,
schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com,
linux390@de.ibm.com, David Miller <davem@davemloft.net>,
Rob Herring <rob.herring@calxeda.com>,
Arnd Bergmann <arnd@arndb.de>,
Stephen Warren <swarren@nvidia.com>,
john.stultz@linaro.org, jesper.nilsson@axis.com,
gregkh@linuxfoundation.org, sam@ravnborg.org,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
lkml <linux-kernel@vger.kernel.org>,
linux-m32r@ml.linux-m32r.org, linux-m32r-ja@ml.linux-m32r.org,
linux-m68k@vger.kernel.org, linux-s390@vger.kernel.org,
sparclinux@vger.kernel.org, mattw@codeaurora.org
Subject: Re: [PATCH 2/2] Convert PowerPC macro spin_event_timeout() to architecture independent macro
Date: Wed, 31 Jul 2013 17:16:49 -0700 [thread overview]
Message-ID: <51F9A8F1.9020704@codeaurora.org> (raw)
In-Reply-To: <51F9A80E.5010307@tabi.org>
On 07/31/13 17:13, Timur Tabi wrote:
> On 07/31/2013 07:04 PM, Stephen Boyd wrote:
>> If it yields why are we using udelay? Why not usleep_range()? It would
>> be useful to have a variant that worked in interrupt context and it
>> looked like that was almost possible.
> I've never heard of usleep_range() before, so I don't know if it
> applies. Apparently, udelay() includes its own call to cpu_relax(). Is
> it possible that cpu_relax() is a "lightweight" yield, compared to sleeping?
cpu_relax() is usually just a compiler barrier or an instruction hint to
the cpu that it should cool down because we're spinning in a tight loop.
It certainly shouldn't be calling into the scheduler.
>
> FYI, you might want to look at the code reviews for spin_event_timeout()
> on the linuxppc-dev mailing list, back in March 2009.
>
Sure. Any pointers? Otherwise I'll go digging around the archives.
--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted by The Linux Foundation
WARNING: multiple messages have this Message-ID (diff)
From: Stephen Boyd <sboyd@codeaurora.org>
To: linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 2/2] Convert PowerPC macro spin_event_timeout() to architecture independent macro
Date: Thu, 01 Aug 2013 00:16:49 +0000 [thread overview]
Message-ID: <51F9A8F1.9020704@codeaurora.org> (raw)
In-Reply-To: <51F9A80E.5010307@tabi.org>
On 07/31/13 17:13, Timur Tabi wrote:
> On 07/31/2013 07:04 PM, Stephen Boyd wrote:
>> If it yields why are we using udelay? Why not usleep_range()? It would
>> be useful to have a variant that worked in interrupt context and it
>> looked like that was almost possible.
> I've never heard of usleep_range() before, so I don't know if it
> applies. Apparently, udelay() includes its own call to cpu_relax(). Is
> it possible that cpu_relax() is a "lightweight" yield, compared to sleeping?
cpu_relax() is usually just a compiler barrier or an instruction hint to
the cpu that it should cool down because we're spinning in a tight loop.
It certainly shouldn't be calling into the scheduler.
>
> FYI, you might want to look at the code reviews for spin_event_timeout()
> on the linuxppc-dev mailing list, back in March 2009.
>
Sure. Any pointers? Otherwise I'll go digging around the archives.
--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted by The Linux Foundation
WARNING: multiple messages have this Message-ID (diff)
From: sboyd@codeaurora.org (Stephen Boyd)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 2/2] Convert PowerPC macro spin_event_timeout() to architecture independent macro
Date: Wed, 31 Jul 2013 17:16:49 -0700 [thread overview]
Message-ID: <51F9A8F1.9020704@codeaurora.org> (raw)
In-Reply-To: <51F9A80E.5010307@tabi.org>
On 07/31/13 17:13, Timur Tabi wrote:
> On 07/31/2013 07:04 PM, Stephen Boyd wrote:
>> If it yields why are we using udelay? Why not usleep_range()? It would
>> be useful to have a variant that worked in interrupt context and it
>> looked like that was almost possible.
> I've never heard of usleep_range() before, so I don't know if it
> applies. Apparently, udelay() includes its own call to cpu_relax(). Is
> it possible that cpu_relax() is a "lightweight" yield, compared to sleeping?
cpu_relax() is usually just a compiler barrier or an instruction hint to
the cpu that it should cool down because we're spinning in a tight loop.
It certainly shouldn't be calling into the scheduler.
>
> FYI, you might want to look at the code reviews for spin_event_timeout()
> on the linuxppc-dev mailing list, back in March 2009.
>
Sure. Any pointers? Otherwise I'll go digging around the archives.
--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted by The Linux Foundation
next prev parent reply other threads:[~2013-08-01 0:16 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-07-30 12:38 [PATCH 0/2] Make PPC macro spin_event_timeout() architecture independent Arpit Goel
2013-07-30 12:50 ` Arpit Goel
2013-07-30 12:38 ` Arpit Goel
2013-07-30 12:38 ` Arpit Goel
2013-07-30 12:38 ` [PATCH 1/2] Make USECS_PER_JIFFY available for generic use Arpit Goel
2013-07-30 12:50 ` Arpit Goel
2013-07-30 12:38 ` Arpit Goel
2013-07-30 12:38 ` Arpit Goel
2013-07-30 12:38 ` [PATCH 2/2] Convert PowerPC macro spin_event_timeout() to architecture independent macro Arpit Goel
2013-07-30 12:50 ` Arpit Goel
2013-07-30 12:38 ` Arpit Goel
2013-07-30 12:38 ` Arpit Goel
2013-07-31 7:16 ` Stephen Boyd
2013-07-31 7:16 ` Stephen Boyd
2013-07-31 7:16 ` Stephen Boyd
2013-07-31 23:44 ` Timur Tabi
2013-07-31 23:44 ` Timur Tabi
2013-07-31 23:44 ` Timur Tabi
2013-07-31 23:44 ` Timur Tabi
2013-08-01 0:04 ` Stephen Boyd
2013-08-01 0:04 ` Stephen Boyd
2013-08-01 0:04 ` Stephen Boyd
2013-08-01 0:13 ` Timur Tabi
2013-08-01 0:13 ` Timur Tabi
2013-08-01 0:13 ` Timur Tabi
2013-08-01 0:16 ` Stephen Boyd [this message]
2013-08-01 0:16 ` Stephen Boyd
2013-08-01 0:16 ` Stephen Boyd
2013-08-01 0:20 ` Timur Tabi
2013-08-01 0:20 ` Timur Tabi
2013-08-01 0:20 ` Timur Tabi
2013-08-01 1:36 ` Stephen Boyd
2013-08-01 1:36 ` Stephen Boyd
2013-08-01 1:36 ` Stephen Boyd
2013-08-01 6:27 ` Srivastava Rajan-B34330
2013-08-01 6:27 ` Srivastava Rajan-B34330
2013-08-01 9:26 ` Goel Arpit-B44344
2013-08-01 9:26 ` Goel Arpit-B44344
2013-08-01 0:02 ` Timur Tabi
2013-08-01 0:02 ` Timur Tabi
2013-08-01 0:02 ` Timur Tabi
2013-08-01 4:38 ` Goel Arpit-B44344
2013-08-01 4:38 ` Goel Arpit-B44344
2013-08-01 4:43 ` Timur Tabi
2013-08-01 4:43 ` Timur Tabi
2013-07-30 13:08 ` [PATCH 0/2] Make PPC macro spin_event_timeout() architecture independent Geert Uytterhoeven
2013-07-30 13:08 ` Geert Uytterhoeven
2013-07-30 13:08 ` Geert Uytterhoeven
2013-07-30 13:08 ` Geert Uytterhoeven
2013-07-31 11:09 ` Goel Arpit-B44344
2013-07-31 11:09 ` Goel Arpit-B44344
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