ipmi patch for review

[John Baldwin]

On Friday, September 20, 2013 1:44:52 am Gleb Smirnoff wrote:
>   John,
> 
> On Thu, Sep 19, 2013 at 03:04:46PM -0400, John Baldwin wrote:
> J> >   When system is writing a kernel core dump, it issues watchdog
> J> > pat wdog_kern_pat(WD_LASTVAL). If ipmi is in action, it registers
> J> > ipmi_wd_event() as event for watchdog. Thus ipmi_wd_event() is
> J> > called in dumping context.
> J> > 
> J> > The problem is that ipmi_wd_event() calls into ipmi_set_watchdog(),
> J> > that calls into ipmi_alloc_request(), which uses M_WAITOK and
> J> > thus sleeps. This is a smaller problem, since can be converted to
> J> > M_NOWAIT. But ipmi_set_watchdog() then calls into
> J> > ipmi_submit_driver_request(), which calls msleep() any time.
> J> > 
> J> >   The attached patch allows me to successfully write cores in
> J> > presence of IPMI.
> J> 
> J> Of course, the watchdog might go off during your dump. :)
> 
> Yes, I understand that :(
> 
> But, imho patch improves situation, although is ugly.

Yes, I think a temporary workaround is fine for now.

> J> The real fix is more complicated, which is that we should not use
> J> a worker thread for at least SMIC and KCS.
> 
> -- 
> Totus tuus, Glebius.
> 

-- 
John Baldwin