linux-kernel - Re: [PATCH 1/2] kill-the-bkl/reiserfs: acquire the inode mutex safely

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Date:	Fri, 05 Jun 2009 15:30:04 -0400
From:	Jeff Mahoney <jeffm@...e.com>
To:	"Trenton D. Adams" <trenton.d.adams@...il.com>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Reiserfs <reiserfs-devel@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Chris Mason <chris.mason@...cle.com>,
	Ingo Molnar <mingo@...e.hu>,
	Alexander Beregalov <a.beregalov@...il.com>
Subject: Re: [PATCH 1/2] kill-the-bkl/reiserfs: acquire the inode mutex safely

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Trenton D. Adams wrote:
> FYI: I never did anything specific that I knew of, so I didn't
> actually notice a delay.  I was rsyncing to a USB key at the time.
> And seeing it took over an hour, I walked away, so I wouldn't have
> noticed it.  But, I could fiddle around a little to see if I could get
> some sort of delay going on.  Any ideas on what I should try?  Then I
> can do the sysreq+t for you if I can reproduce.

Well if the rsync triggered it, that's a good start. 

Try applying the following patch as well. It will cause the hung task detector
to do a sysrq+t automatically so it's not as much of a guessing game. You'll need to boot with 
hung_task_show_state=1.

- -Jeff

- ---
 kernel/hung_task.c |   11 +++++++++++
 1 file changed, 11 insertions(+)

- --- a/kernel/hung_task.c
+++ b/kernel/hung_task.c
@@ -56,6 +56,14 @@ static int __init hung_task_panic_setup(
 }
 __setup("hung_task_panic=", hung_task_panic_setup);
 
+unsigned int __read_mostly sysctl_hung_task_show_state;
+static int __init hung_task_show_state_setup(char *str)
+{
+	sysctl_hung_task_show_state = simple_strtoul(str, NULL, 0);
+	return 1;
+}
+__setup("hung_task_show_state=", hung_task_show_state_setup);
+
 static int
 hung_task_panic(struct notifier_block *this, unsigned long event, void *ptr)
 {
@@ -102,6 +110,9 @@ static void check_hung_task(struct task_
 
 	touch_nmi_watchdog();
 
+	if (sysctl_hung_task_show_state)
+		show_state();
+
 	if (sysctl_hung_task_panic)
 		panic("hung_task: blocked tasks");
 }

- -- 
Jeff Mahoney
SUSE Labs
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