From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sebastian Andrzej Siewior Subject: Re: Suspend resume problem (WAS Re: [ANNOUNCE] 3.8.10-rt6) Date: Fri, 03 May 2013 11:59:32 +0200 Message-ID: <51838A84.90500@linutronix.de> References: <20130429201202.GB7979@linutronix.de> <20130429161925.2a6ea78a@riff.lan> <20130430170948.GB4688@linutronix.de> <1367345295.30667.68.camel@gandalf.local.home> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: Clark Williams , linux-rt-users , Thomas Gleixner , LKML To: Steven Rostedt Return-path: In-Reply-To: <1367345295.30667.68.camel@gandalf.local.home> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-rt-users.vger.kernel.org On 04/30/2013 08:08 PM, Steven Rostedt wrote: >> This NMI releated deadlock is a problem which should also trigger >> mainline, right? > > Well, yeah, as sending out a NMI stack dump is sorta the last resort, > and is dangerous to do printks from NMI context. So we did bad and we upgrade to bad and dangerous. >> >> Now, the time jump on the other hand is the real issue here and is >> RT-only. It looks like we get a big number of timer updates via >> tick_do_update_jiffies64() because according to ktime_get() that much >> time really passed by. > > As the NMI dump only happens because of the time jump, which as you > said, is -rt only, I wouldn't say that the NMI deadlock is a mainline > bug. The reason for the NMI was a bug in the -RT tree but if something else triggers that NMI we have a good chance to deadlock. What about a try_lock() and leave after 50 usecs of trying and not getting it in the in_nmi() case? > -- Steve Sebastian