From: Thomas Gleixner <tglx@linutronix.de>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Lai Jiangshan <laijs@cn.fujitsu.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>
Subject: Re: [patch 2/2] rtmutex: Avoid pointless requeueing in the deadlock detection chain walk
Date: Tue, 20 May 2014 09:43:56 +0900 (JST) [thread overview]
Message-ID: <alpine.DEB.2.02.1405200936320.7325@ionos.tec.linutronix.de> (raw)
In-Reply-To: <20140515130435.24132d1b@gandalf.local.home>
On Thu, 15 May 2014, Steven Rostedt wrote:
> On Wed, 14 May 2014 20:03:27 -0000
> Thomas Gleixner <tglx@linutronix.de> wrote:
>
> > In case the dead lock detector is enabled we follow the lock chain to
> > the end in rt_mutex_adjust_prio_chain, even if we could stop earlier
> > due to the priority/waiter constellation.
>
> I'm assuming that we want to detect deadlocks for all futex calls
> even when CONFIG_DEBUG_RT_MUTEXES is set?
>
> In kernel/locking/rtmutex_common.h:
>
> #ifdef CONFIG_DEBUG_RT_MUTEXES
> # include "rtmutex-debug.h"
> #else
> # include "rtmutex.h"
> #endif
>
> In kernel/locking/rtmutex.h:
>
> #define debug_rt_mutex_detect_deadlock(w,d) (d)
>
> In kernel/locking/rtmutex.h:
>
> static inline int debug_rt_mutex_detect_deadlock(struct rt_mutex_waiter *waiter,
> int detect)
> {
> return (waiter != NULL);
> }
>
> Shouldn't that be: return detect || waiter != NULL;
>
No. We do not care about whether the caller handed in detect or not.
>
> I know this a separate issue from this patch series, but it's
> something that I just noticed.
It's not really intuitive. We might make the call sites hand in
constants. RTMUTEX_DETECT_DEADLOCK, RTMUTEX_IGNORE_DEADLOCK or
something like that and switch it depending on
CONFIG_DEBUG_RT_MUTEXES.
Thanks,
tglx
next prev parent reply other threads:[~2014-05-20 0:43 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-14 20:03 [patch 0/2] rtmutex: Fix the deadlock detector for real Thomas Gleixner
2014-05-14 20:03 ` [patch 1/2] rtmutex: Fix " Thomas Gleixner
2014-05-14 20:03 ` [patch 2/2] rtmutex: Avoid pointless requeueing in the deadlock detection chain walk Thomas Gleixner
2014-05-15 6:47 ` Ingo Molnar
2014-05-15 21:49 ` Steven Rostedt
2014-05-15 17:04 ` Steven Rostedt
2014-05-20 0:43 ` Thomas Gleixner [this message]
2014-05-20 1:29 ` Steven Rostedt
2014-05-15 21:39 ` Steven Rostedt
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