From: Andrea Arcangeli <andrea@novell.com>
To: Chris Wright <chrisw@osdl.org>
Cc: mingo@elte.hu, johansen@immunix.com,
Stephen Smalley <sds@epoch.ncsc.mil>,
Thomas Bleher <bleher@informatik.uni-muenchen.de>,
linux-kernel@vger.kernel.org
Subject: Re: [RFC][PATCH] delay rq_lock acquisition in setscheduler
Date: Thu, 21 Oct 2004 04:00:22 +0200 [thread overview]
Message-ID: <20041021020022.GB8756@dualathlon.random> (raw)
In-Reply-To: <20041020183238.U2357@build.pdx.osdl.net>
On Wed, Oct 20, 2004 at 06:32:38PM -0700, Chris Wright wrote:
> + rq = task_rq_lock(p, &flags);
> + /* recheck policy now with rq lock held */
> + retval = -EPERM;
> + if (unlikely(oldpolicy != -1 && oldpolicy != p->policy))
> + goto out_unlock_rq;
to be really backwards compatible you should return 0 methinks, the only
case when this race can trigger is with non deterministic usage, and the
current kernel would never return -EPERM in such a non deterministic
usage. However the -EPERM will signal the non deterministic usage, but I
doubt it worth to return -EPERM there, since it makes it looks like the
other side that didn't get EPERM is safe while it's not, since the other
side isn't deterministic either.
next prev parent reply other threads:[~2004-10-21 2:00 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-10-21 1:32 [RFC][PATCH] delay rq_lock acquisition in setscheduler Chris Wright
2004-10-21 2:00 ` Andrea Arcangeli [this message]
2004-10-21 5:16 ` Chris Wright
2004-10-21 12:53 ` Andrea Arcangeli
2004-10-21 7:56 ` Ingo Molnar
2004-10-21 17:25 ` Chris Wright
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