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Date: Fri, 20 Sep 2013 09:44:52 +0400
From: Gleb Smirnoff <glebius@FreeBSD.org>
To: John Baldwin <jhb@freebsd.org>
Subject: Re: ipmi patch for review
Message-ID: <20130920054452.GB4574@glebius.int.ru>
References: <20130917102110.GK4574@glebius.int.ru>
 <201309191504.46986.jhb@freebsd.org>
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  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.

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.