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Date: Tue, 17 Sep 2013 14:21:10 +0400
From: Gleb Smirnoff <glebius@FreeBSD.org>
To: current@FreeBSD.org
Subject: ipmi patch for review
Message-ID: <20130917102110.GK4574@glebius.int.ru>
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  Hi!

  When system is writing a kernel core dump, it issues watchdog
pat wdog_kern_pat(WD_LASTVAL). If ipmi is in action, it registers
ipmi_wd_event() as event for watchdog. Thus ipmi_wd_event() is
called in dumping context.

The problem is that ipmi_wd_event() calls into ipmi_set_watchdog(),
that calls into ipmi_alloc_request(), which uses M_WAITOK and
thus sleeps. This is a smaller problem, since can be converted to
M_NOWAIT. But ipmi_set_watchdog() then calls into
ipmi_submit_driver_request(), which calls msleep() any time.

  The attached patch allows me to successfully write cores in
presence of IPMI.

-- 
Totus tuus, Glebius.

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Index: dev/ipmi/ipmi.c
===================================================================
--- dev/ipmi/ipmi.c	(revision 255625)
+++ dev/ipmi/ipmi.c	(working copy)
@@ -647,6 +647,9 @@ ipmi_wd_event(void *arg, unsigned int cmd, int *er
 	unsigned int timeout;
 	int e;
 
+	if (dumping)
+		return;
+
 	cmd &= WD_INTERVAL;
 	if (cmd > 0 && cmd <= 63) {
 		timeout = ((uint64_t)1 << cmd) / 1000000000;

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