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Date: Tue, 20 May 2014 09:43:56 +0900 (JST) From: Thomas Gleixner <tglx@...utronix.de> To: Steven Rostedt <rostedt@...dmis.org> 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 Thu, 15 May 2014, Steven Rostedt wrote: > On Wed, 14 May 2014 20:03:27 -0000 > Thomas Gleixner <tglx@...utronix.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 -- 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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