From: Esben Nielsen <simlo@phys.au.dk>
To: Bill Huey <billh@gnuppy.monkey.org>
Cc: Ingo Molnar <mingo@elte.hu>, Steven Rostedt <rostedt@goodmis.org>,
david singleton <dsingleton@mvista.com>,
<linux-kernel@vger.kernel.org>
Subject: Re: RT Mutex patch and tester [PREEMPT_RT]
Date: Mon, 16 Jan 2006 09:35:42 +0100 (MET) [thread overview]
Message-ID: <Pine.LNX.4.44L0.0601160926360.4219-100000@lifa01.phys.au.dk> (raw)
In-Reply-To: <20060115042449.GA9871@gnuppy.monkey.org>
On Sat, 14 Jan 2006, Bill Huey wrote:
> On Wed, Jan 11, 2006 at 06:25:36PM +0100, Esben Nielsen wrote:
> > So how many locks do we have to worry about? Two.
> > One for locking the lock. One for locking various PI related data on the
> > task structure, as the pi_waiters list, blocked_on, pending_owner - and
> > also prio.
> > Therefore only lock->wait_lock and sometask->pi_lock will be locked at the
> > same time. And in that order. There is therefore no spinlock deadlocks.
> > And the code is simpler.
>
> Ok, got a question. How do deal with the false reporting and handling of
> a lock circularity window involving the handoff of task A's BKL to another
> task B ? Task A is blocked trying to get a mutex owned by task B, task A
> is block B since it owns BKL which task B is contending on. It's not a
> deadlock since it's a hand off situation.
>
I am not precisely sure what you mean by "false reporting".
Handing off BKL is done in schedule() in sched.c. I.e. if B owns a normal
mutex, A will give BKL to B when A calls schedule() in the down-operation
of that mutex.
> I didn't see any handling of this case in the code and I was wondering
> if the traversal logic you wrote avoids this case as an inherent property
> and I missed that stuff ?
The stuff is in kernel/sched.c and lib/kernel_lock.c.
>
> bill
>
> -
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next prev parent reply other threads:[~2006-01-16 8:36 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-01-11 17:25 RT Mutex patch and tester [PREEMPT_RT] Esben Nielsen
2006-01-11 17:51 ` Steven Rostedt
2006-01-11 21:45 ` Esben Nielsen
2006-01-12 11:33 ` Bill Huey
2006-01-12 12:54 ` Esben Nielsen
2006-01-13 8:07 ` Bill Huey
2006-01-13 8:47 ` Esben Nielsen
2006-01-13 10:19 ` Bill Huey
2006-01-15 4:24 ` Bill Huey
2006-01-16 8:35 ` Esben Nielsen [this message]
2006-01-16 10:22 ` Bill Huey
2006-01-16 10:53 ` Bill Huey
2006-01-16 11:30 ` Esben Nielsen
[not found] ` <Pine.LNX.4.44L0.0601181120100.1993-201000@lifa02.phys.au.dk>
2006-01-18 10:38 ` Ingo Molnar
2006-01-18 12:49 ` Steven Rostedt
2006-01-18 14:18 ` Esben Nielsen
[not found] ` <Pine.LNX.4.44L0.0601230047290.31387-201000@lifa01.phys.au.dk>
2006-01-23 0:38 ` david singleton
2006-01-23 2:04 ` Bill Huey
2006-01-23 9:33 ` Esben Nielsen
2006-01-23 14:23 ` Steven Rostedt
2006-01-23 15:14 ` Esben Nielsen
2006-01-27 15:18 ` Esben Nielsen
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