Messages in this thread | | | Date | Wed, 18 Jun 2014 07:44:57 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [RFC PATCH 00/11] printk: safe printing in NMI context |
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On Wed, Jun 18, 2014 at 04:41:09PM +0200, Jiri Kosina wrote: > On Wed, 18 Jun 2014, Paul E. McKenney wrote: > > > > - both RCU stall detector and 'echo l > sysrq-trigger' can (and we've > > > seen it happening for real) cause a complete, undebuggable, silent hang > > > of machine (deadlock in NMI context) > > > > I could easily add an option to RCU to allow people to tell it not to > > use NMIs to dump the stack. Would that help? > > Well, that would make unfortunately the information provided by RCU stall > detector rather useless ... workqueue-based stack dumping is very unlikely > to point its finger to the real offender, as it'd be coming way too late.
I would not use workqueues, but rather have the CPU detecting the stall grovel through the other CPUs' stacks, which is what I do now for architectures that don't support NMI-based stack dumps. Would that be a reasonable approach?
Thanx, Paul
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