From: Ralf Baechle <ralf@linux-mips.org>
To: David Daney <ddaney@avtrex.com>
Cc: Fuxin Zhang <fxzhang@ict.ac.cn>, linux-mips@linux-mips.org
Subject: Re: cmpxchg broken in some situation
Date: Mon, 1 Oct 2007 11:24:33 +0100 [thread overview]
Message-ID: <20071001102433.GA20219@linux-mips.org> (raw)
In-Reply-To: <4700708B.8070708@avtrex.com>
On Sun, Sep 30, 2007 at 08:59:07PM -0700, David Daney wrote:
> David Daney wrote:
> >Ralf Baechle wrote:
> >>+ } else if (cpu_has_llsc) { \
> >>+ __asm__ __volatile__( \
> >>+ " .set push \n" \
> >>+ " .set noat \n" \
> >>+ " .set mips3 \n" \
> >>+ "1: " ld " %0, %2 # __cmpxchg_u32 \n" \
> >>+ " bne %0, %z3, 2f \n" \
> >>+ " .set mips0 \n" \
> >>+ " move $1, %z4 \n" \
> >>+ " .set mips3 \n" \
> >>+ " " st " $1, %1 \n" \
> >>+ " beqz $1, 3f \n" \
> >>+ "2: \n" \
> >>+ " .subsection 2 \n" \
> >>+ "3: b 1b \n" \
> >>+ " .previous \n" \
> >>+ " .set pop \n" \
> >>+ : "=&r" (__ret), "=R" (*m) \
> >>+ : "R" (*m), "Jr" (old), "Jr" (new) \
> >>+ : "memory"); \
> >>
> >Is a 'sync' needed after the 'sc'?
> >
> >According to this message:
> >http://www.linux-mips.org/cgi-bin/mesg.cgi?a=linux-mips&i=20070919084515.GM9972%40networkno.de
> >
> >it would seem so.
>
> Drat, I probably posted too soon. That is the smp_llsc_mb(); isn't it.
Yes - and the answer to your original question is a clear and definate
maybe ;-)
In the kernel we can afford to optimize for every piece of silicon on earth.
In userspace we can't make that sort of compile time choices as easily so
it's a better idea to just litter a few SYNCs over the code.
Ralf
next prev parent reply other threads:[~2007-10-01 10:24 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-09-30 10:34 cmpxchg broken in some situation Fuxin Zhang
2007-10-01 2:53 ` Ralf Baechle
2007-10-01 3:56 ` David Daney
2007-10-01 3:59 ` David Daney
2007-10-01 10:24 ` Ralf Baechle [this message]
2007-10-01 15:11 ` Fuxin Zhang
2007-10-01 15:26 ` Ralf Baechle
2007-10-02 9:34 ` Fuxin Zhang
2007-10-02 10:35 ` Ralf Baechle
2007-10-02 14:22 ` Thiemo Seufer
2007-10-02 23:15 ` Ralf Baechle
2007-10-02 22:48 ` Fuxin Zhang
2007-10-02 22:52 ` Ralf Baechle
2007-10-02 23:07 ` Fuxin Zhang
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