From: David Howells <dhowells@redhat.com>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: bwatson@kahuna.cag.cpqcorp.net, marcelo@conectiva.com.br,
linux-kernel@vger.kernel.org, dhowells@redhat.com,
hch@caldera.de
Subject: Re: [PATCH] 2.4.18-pre9, trylock for read/write semaphores
Date: Wed, 13 Feb 2002 07:47:32 +0000 [thread overview]
Message-ID: <26100.1013586452@warthog.cambridge.redhat.com> (raw)
In-Reply-To: Message from Alan Cox <alan@lxorguk.ukuu.org.uk> of "Tue, 12 Feb 2002 23:29:29 GMT." <E16amMb-0003RQ-00@the-village.bc.nu>
> > + new = old + RWSEM_ACTIVE_READ_BIAS;
> > + if (cmpxchg(&sem->count, old, new) == old)
> > + return 1;
>
> cmpxchg isnt present on i386
This isn't actually relevant... <asm/rwsem.h> isn't actually used unless
CONFIG_RWSEM_GENERIC_SPINLOCK is turned off, which it isn't if the CPU type is
configured to "i386":
[arch/i386/config.in]
if [ "$CONFIG_M386" = "y" ]; then
define_bool CONFIG_X86_CMPXCHG n
define_bool CONFIG_X86_XADD n
define_int CONFIG_X86_L1_CACHE_SHIFT 4
define_bool CONFIG_RWSEM_GENERIC_SPINLOCK y
define_bool CONFIG_RWSEM_XCHGADD_ALGORITHM n
else
define_bool CONFIG_X86_WP_WORKS_OK y
define_bool CONFIG_X86_INVLPG y
define_bool CONFIG_X86_CMPXCHG y
define_bool CONFIG_X86_XADD y
define_bool CONFIG_X86_BSWAP y
define_bool CONFIG_X86_POPAD_OK y
define_bool CONFIG_RWSEM_GENERIC_SPINLOCK n
define_bool CONFIG_RWSEM_XCHGADD_ALGORITHM y
fi
[include/linux/rwsem.h]
#ifdef CONFIG_RWSEM_GENERIC_SPINLOCK
#include <linux/rwsem-spinlock.h> /* use a generic implementation */
#else
#include <asm/rwsem.h> /* use an arch-specific implementation */
#endif
David
next prev parent reply other threads:[~2002-02-13 7:48 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-02-12 22:45 [PATCH] 2.4.18-pre9, trylock for read/write semaphores bwatson
2002-02-12 23:29 ` Alan Cox
2002-02-13 1:47 ` Brian J. Watson
2002-02-13 7:47 ` David Howells [this message]
2002-02-13 8:19 ` David Howells
2002-02-14 0:13 ` Brian J. Watson
2002-02-21 18:04 Kendrick M. Smith
2002-02-21 21:54 ` Brian J. Watson
2002-02-21 23:02 ` Kendrick M. Smith
2002-02-21 23:26 ` Brian J. Watson
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