Bug 9371

Summary: Reproducable hang with 2.6.24-rc2 using oprofile
Product: Platform Specific/Hardware Reporter: Rafael J. Wysocki (rjwysocki)
Component: i386Assignee: Ingo Molnar (mingo)
Status: CLOSED CODE_FIX    
Severity: normal CC: jack, mingo, tglx
Priority: P1    
Hardware: All   
OS: Linux   
Kernel Version: 2.6.24-rc2 Subsystem:
Regression: Yes Bisected commit-id:
Bug Depends on:    
Bug Blocks: 9243    

Description Rafael J. Wysocki 2007-11-13 13:18:47 UTC 
Subject         : Reproducable hang with 2.6.24-rc2 using oprofile
Submitter       : Jan Kara <jack@suse.cz>
References      : http://lkml.org/lkml/2007/11/13/225
Comment 1 Jan Kara 2007-11-19 08:35:13 UTC 
I've bisected a bit and the following commit is the one causing it:

commit 574a60421c8ea5383a54ebee1f37fa871d00e1b9
Author: Jan Blunck <jblunck@suse.de>
Date:   Fri Oct 19 20:35:03 2007 +0200

    i386: make callgraph use dump_trace() on i386/x86_64
Comment 2 Ingo Molnar 2007-11-20 01:07:50 UTC 
does 2.6.24-rc3 fix it? It has an oprofile fix:

| commit df9d177aa28d50e64bae6fbd6b263833079e3571
| Author: Philippe Elie <phil.el@wanadoo.fr>
| Date:   Wed Nov 14 16:58:48 2007 -0800
|
|    oProfile: oops when profile_pc() returns ~0LU

if that does not help then we'll revert the commit you bisected so excellently.
Comment 3 Jan Kara 2007-11-20 02:07:31 UTC 
It helps! The kernel does not hang any more and I'm even able to get some numbers from oprofile :). Thanks. I just wonder how come I didn't see any message on the console - I used standard VGA console to maximize the possibility I'd see something before hang...
Comment 4 Ingo Molnar 2007-11-20 02:39:50 UTC 
profiling might crash in places where the crash handler itself profiles too, etc. - resulting in a hard hang.

nmi_watchdog=2 (or =1) could perhaps have gotten a backtrace.