From: David Mosberger <davidm@napali.hpl.hp.com>
To: linux-ia64@vger.kernel.org
Subject: Re: [Linux-ia64] spin_unlock() problem
Date: Mon, 07 Apr 2003 21:14:05 +0000 [thread overview]
Message-ID: <marc-linux-ia64-105590723705427@msgid-missing> (raw)
In-Reply-To: <marc-linux-ia64-105590723705414@msgid-missing>
>>>>> On 04 Apr 2003 10:13:25 -0500, Jes Sorensen <jes@wildopensource.com> said:
Jes> The first example I sent out was clearly bogus, please ignore
Jes> it. I am still pondering the second one. Jack pointed out in
Jes> private email that the release semantics of setting a volatible
Jes> variable should take care of it, but I am still trying to grasp
Jes> it.
In your example:
cpu1()
{
spin_lock(&bleh);
*a = foo;
spin_unlock(&bleh);
*b = bar;
}
cpu2()
{
if (*b = bar)
boink(*a);
}
*a is guaranteed to have the value "foo" when *b observes bar.
spin_unlock() has release semantics and that ensures that all
subsequent (in program order) memory operations are observed after the
store with release semantics.
--david
next prev parent reply other threads:[~2003-04-07 21:14 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-04-04 4:51 [Linux-ia64] spin_unlock() problem Jes Sorensen
2003-04-04 5:04 ` Jes Sorensen
2003-04-04 14:43 ` Van Maren, Kevin
2003-04-04 14:49 ` Van Maren, Kevin
2003-04-04 15:13 ` Jes Sorensen
2003-04-07 21:09 ` David Mosberger
2003-04-07 21:14 ` David Mosberger [this message]
2003-04-07 22:09 ` Jes Sorensen
2003-04-07 22:18 ` Luck, Tony
2003-04-07 22:58 ` David Mosberger
2003-04-07 23:13 ` Jes Sorensen
2003-04-07 23:30 ` Jim Hull
2003-04-07 23:38 ` Chen, Kenneth W
2003-04-08 0:14 ` David Mosberger
2003-04-08 0:15 ` David Mosberger
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