Messages in this thread | | | Date | Tue, 28 Sep 2010 11:19:24 -0400 | From | Don Zickus <> | Subject | Re: [PATCH -v2 7/7] x86, NMI, Remove do_nmi_callback logic |
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On Tue, Sep 28, 2010 at 08:28:25AM +0800, Huang Ying wrote: > Hi, Don, > > On Mon, 2010-09-27 at 23:16 +0800, Don Zickus wrote: > > On Mon, Sep 27, 2010 at 03:43:41PM +0200, Robert Richter wrote: > > > On 27.09.10 08:56:44, huang ying wrote: > > > > > > > >> -static int unknown_nmi_panic_callback(struct pt_regs *regs, int cpu) > > > > >> -{ > > > > >> - unsigned char reason = get_nmi_reason(); > > > > >> - char buf[64]; > > > > >> - > > > > >> - sprintf(buf, "NMI received for unknown reason %02x\n", reason); > > > > >> - die_nmi(buf, regs, 1); /* Always panic here */ > > > > >> - return 0; > > > > > > > > > > You are dropping this code that is different to panic(). > > > > > > > > What is the difference? Is it relevant? > > > > > > I think yes, since the code behaves different. Otherwise we could > > > remove die_nmi() completly and replace it by panic(). But both are > > > different implementions. Maybe we can merge the code, but I didn't > > > look at it closly. > > > > Actually die_nmi is a wrapper around panic with two important pieces. > > One, it dumps some registers and two it does another notifier call to > > DIE_NMIWATCHDOG (which correlates to another discussion in this patch > > series). > > > > So if we do any consolidation between panic and die_nmi, it should be > > convert to die_nmi. But then I wonder if that breaks the original > > semantics of 'panic_on_unrecovered_nmi'. I don't think so though. > > Please take a look at the original code: > > > if (nmi_watchdog_tick(regs, reason)) > return; > if (!do_nmi_callback(regs, cpu)) > #endif /* !CONFIG_LOCKUP_DETECTOR */ > unknown_nmi_error(reason, regs); > #else > unknown_nmi_error(reason, regs); > #endif > > If NMI comes from watchdog, nmi_watchdog_tick() will return 1. So > do_nmi_callback() is NOT for watchdog NMI, but for unknown NMI. Why do > we call DIE_NMIWATCHDOG for unknown NMI (NOT watchdog NMI)? die_nmi is > for watchdog, not unknown NMI.
I think watchdog is an overloaded term. I was under the impression that once the nmi watchdog determined a problem, it called the DIE_NMIWATCHDOG die chain to see if any other drivers wanted to clean up or do their thing first before panic'ing (namely drivers in drivers/char/watchdog).
Cheers, Don
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