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Subject: Re: Problem with using spinlocks when kernel is compiled withoutsmp-support
Date: Thu, 8 Dec 2005 11:17:37 -0500
Message-ID: <Pine.LNX.4.61.0512081114380.14141@chaos.analogic.com>
Thread-Topic: Problem with using spinlocks when kernel is compiled withoutsmp-support
Thread-Index: AcX8EufS3hlLc4ISRtWUDyTwNoFYjA==
References: <1134058209.24458.10.camel@noti>
From: "linux-os \(Dick Johnson\)" <linux-os@analogic.com>
To: "Dirk Henning Gerdes" <mail@dirk-gerdes.de>
Cc: "Andrew Morton" <akpm@osdl.org>, "LKML" <linux-kernel@vger.kernel.org>
Reply-To: "linux-os \(Dick Johnson\)" <linux-os@analogic.com>
Sender: linux-kernel-owner@vger.kernel.org
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On Thu, 8 Dec 2005, Dirk Henning Gerdes wrote:

> Hello Andrew!
>
> I have the following problem on 2.6.15-rc5-mm1
>
> When compiling a module using spinlocks I get the following
> error-message, when SMP is disabled in my Kernel-config:
>
>
>
>
> In file included from /home/dirk/Masterarbeit/mynoop/test/mynoop.c:7:
> include/asm/spinlock.h:21:1: warning: "__raw_spin_is_locked" redefined
> In file included from include/linux/spinlock.h:90,
>                 from include/linux/kobject.h:23,
>                 from include/linux/device.h:16,
>                 from include/linux/genhd.h:15,
>                 from include/linux/blkdev.h:6,
>                 from /home/dirk/Masterarbeit/mynoop/test/mynoop.c:1:
> include/linux/spinlock_up.h:61:1: warning: this is the location of the
> previous definition
> In file included from /home/dirk/Masterarbeit/mynoop/test/mynoop.c:7:
> include/asm/spinlock.h:51: error: syntax error before 'do'
> include/asm/spinlock.h: In function '__raw_spin_lock_flags':
> include/asm/spinlock.h:62: error: 'struct <anonymous>' has no member
> named 'slock'
> include/asm/spinlock.h:60: error: invalid lvalue in asm output 0
> include/asm/spinlock.h: At top level:
> include/asm/spinlock.h:65: error: syntax error before '{' token
> include/asm/spinlock.h:89: error: syntax error before 'do'
> In file included from /home/dirk/Masterarbeit/mynoop/test/mynoop.c:7:
> include/asm/spinlock.h:114:1: warning: "__raw_spin_unlock_wait"
> redefined
> In file included from include/linux/spinlock.h:90,
>                 from include/linux/kobject.h:23,
>                 from include/linux/device.h:16,
>                 from include/linux/genhd.h:15,
>                 from include/linux/blkdev.h:6,
>                 from /home/dirk/Masterarbeit/mynoop/test/mynoop.c:1:
> include/linux/spinlock_up.h:71:1: warning: this is the location of the
> previous definition
> In file included from /home/dirk/Masterarbeit/mynoop/test/mynoop.c:7:
> include/asm/spinlock.h:142:1: warning: "__raw_read_can_lock" redefined
> In file included from include/linux/spinlock.h:90,
>                 from include/linux/kobject.h:23,
>                 from include/linux/device.h:16,
>                 from include/linux/genhd.h:15,
>                 from include/linux/blkdev.h:6,
>                 from /home/dirk/Masterarbeit/mynoop/test/mynoop.c:1:
> include/linux/spinlock_up.h:68:1: warning: this is the location of the
> previous definition
> In file included from /home/dirk/Masterarbeit/mynoop/test/mynoop.c:7:
> include/asm/spinlock.h:148:1: warning: "__raw_write_can_lock" redefined
> In file included from include/linux/spinlock.h:90,
>                 from include/linux/kobject.h:23,
>                 from include/linux/device.h:16,
>                 from include/linux/genhd.h:15,
>                 from include/linux/blkdev.h:6,
>                 from /home/dirk/Masterarbeit/mynoop/test/mynoop.c:1:
> include/linux/spinlock_up.h:69:1: warning: this is the location of the
> previous definition
> include/asm/spinlock.h: In function '__raw_read_unlock':
> include/asm/spinlock.h:181: error: 'struct <anonymous>' has no member
> named 'lock'
> include/asm/spinlock.h:181: error: invalid lvalue in asm output 0
> include/asm/spinlock.h: In function '__raw_write_unlock':
> include/asm/spinlock.h:187: error: 'struct <anonymous>' has no member
> named 'lock'
> include/asm/spinlock.h:186: error: invalid lvalue in asm output 0
>
>
>
> shouldn't it be possible to use spinlocks in my code even if I don't
> support SMP for compatiblity ?
>
>
> Dirk

Yes. And it used to be true. Certainly one should never use
cli() and sti() so all you have to protect critical sections
from interrupts are spin-locks. This has been broken for some
time so, I suggest you just enable SMP in your .config and
live with it for the time being.

Cheers,
Dick Johnson
Penguin : Linux version 2.6.13.4 on an i686 machine (5589.55 BogoMips).
Warning : 98.36% of all statistics are fiction.
.

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