Messages in this thread | | | Date | Wed, 18 Jun 2014 09:43:27 -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 12:38:37PM -0400, Steven Rostedt wrote: > On Wed, 18 Jun 2014 09:21:17 -0700 > "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> wrote: > > > On Wed, Jun 18, 2014 at 05:58:40AM -1000, Linus Torvalds wrote: > > > On Jun 18, 2014 4:36 AM, "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> > > > wrote: > > > > > > > > I could easily add an option to RCU to allow people to tell it not to > > > > use NMIs to dump the stack. > > > > > > I don't think it should be an "option". > > > > > > We should stop using nmi as if it was something "normal". It isn't. Code > > > running in nmi context should be special, and should be very very aware > > > that it is special. That goes way beyond "don't use printk". We seem to > > > have gone way way too far in using nmi context. > > > > > > So we should get *rid* of code in nmi context rather than then complain > > > about printk being buggy. > > > > OK, unconditional non-use of NMIs is even easier. ;-) > > > > Something like the following. > > I have found the RCU stalls extremely useful in debugging lockups. In > case this doesn't work as well, I'm willing to write up something that > could send NMIs to all CPUs that would write into the ftrace ring > buffer and when finished, the calling CPU can dump it out. No printk > from NMI context at all.
Sounds like a good plan to me!
Thanx, Paul
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