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Date: Mon, 19 May 2014 21:29:16 -0400 From: Steven Rostedt <rostedt@...dmis.org> To: Thomas Gleixner <tglx@...utronix.de> Cc: LKML <linux-kernel@...r.kernel.org>, Lai Jiangshan <laijs@...fujitsu.com>, Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org> Subject: Re: [patch 2/2] rtmutex: Avoid pointless requeueing in the deadlock detection chain walk On Tue, 2014-05-20 at 09:43 +0900, Thomas Gleixner wrote: > 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. Bah, you're right. I was getting confused between try_to_take_rt_mutex() and task_blocks_on_rt_mutex(). The former passes in a NULL waiter when taking the first time, but it's the task_blocks_on_rt_mutex() that does the test, and yes, the waiter is never NULL when boosting. I may send you a patch to add comments to these little idiosyncrasies. > > > > > 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. Yes it is confusing. I use to know this code really well, and now over the years, it's not something to look at quickly and produce a comprehensive response. The sad part is, I looked at it quite a bit before sending my response and I still got confused :-p -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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