Messages in this thread | | | Date | Fri, 7 Sep 2018 17:35:38 +0900 | From | Sergey Senozhatsky <> | Subject | Re: [PATCH] printk/tracing: Do not trace printk_nmi_enter() |
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On (09/07/18 10:28), Petr Mladek wrote: > On Fri 2018-09-07 09:45:31, Peter Zijlstra wrote: > > On Thu, Sep 06, 2018 at 11:31:51AM +0900, Sergey Senozhatsky wrote: > > > An alternative option, thus, could be re-instating back the rule that > > > lockdep_off/on should be the first and the last thing we do in > > > nmi_enter/nmi_exit. E.g. > > > > > > nmi_enter() > > > lockdep_off(); > > > printk_nmi_enter(); > > > > > > nmi_exit() > > > printk_nmi_exit(); > > > lockdep_on(); > > > > Yes that. Also, those should probably be inline functions. > > > > --- > > Subject: locking/lockdep: Fix NMI handling > > > > Someone put code in the NMI handler before lockdep_off(). Since lockdep > > is not NMI safe, this wrecks stuff. > > My view is that nmi_enter() has to switch several features into > NMI-safe mode. The code must not trigger the other features when > they are still in the unsafe mode. > > It is a chicken&egg problem. And it is hard to completely prevent > regressions caused by future changes. > > I though that printk_nmi_enter() should never need any lockdep-related > code. On the other hand, people might want to printk debug messages > when lockdep_off() is called. This is why I put it in the current order. > > That said, I am not against this change. Especially the inlining > is a good move. Note that lockdep_off()/lockdep_on() must not > be traced as well.
Should't printk_nmi_enter()/printk_nmi_exit() still be notrace? Like you and Steven said - it's still before ftrace_nmi_enter() and should be notrace regardless.
-ss
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