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From: Mariusz Kozlowski <m.kozlowski@tuxland.pl>
To: Josh Triplett <josh@freedesktop.org>
Subject: Re: 2.6.23-rc2-mm1: sleeping function called from invalid context at kernel/mutex.c:86
Date: Fri, 10 Aug 2007 09:27:08 +0200
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Cc: Andrew Morton <akpm@linux-foundation.org>, linux-kernel@vger.kernel.org,
       Ingo Molnar <mingo@elte.hu>, "Randy.Dunlap" <rdunlap@xenotime.net>
References: <20070809015106.cd0bfc53.akpm@linux-foundation.org> <20070809171128.03f40dff.akpm@linux-foundation.org> <46BBF965.5030203@freedesktop.org>
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> >> 	This probably doesn't have great impact ;) but ...
> >> To reproduce: run torture tests for RCU and then sysrq+q.
> >>
> >> SysRq : Show Pending Timers
> >> Timer List Version: v0.3
> >> HRTIMER_MAX_CLOCK_BASES: 2
> >> now at 1764338760370 nsecs
> >>
> >> cpu: 0
> >>  clock 0:
> >>   .index:      0
> >>   .resolution: 1 nsecs
> >>   .get_time:   ktime_get_real
> >>   .offset:     1186699025823815427 nsecs
> >> active timers:
> >>  clock 1:
> >>   .index:      1
> >>   .resolution: 1 nsecs
> >>   .get_time:   ktime_get
> >>   .offset:     0 nsecs
> >> active timers:
> >>  #0: <3>BUG: sleeping function called from invalid context at kernel/mutex.c:86
> >> in_atomic():1, irqs_disabled():1
> >> INFO: lockdep is turned off.
> >> irq event stamp: 0
> >> hardirqs last  enabled at (0): [<00000000>] 0x0
> >> hardirqs last disabled at (0): [<c0117def>] copy_process+0x4a8/0x144c
> >> softirqs last  enabled at (0): [<c0117e0d>] copy_process+0x4c6/0x144c
> >> softirqs last disabled at (0): [<00000000>] 0x0
> >>  [<c0104869>] show_trace_log_lvl+0x1a/0x30
> >>  [<c01053ad>] show_trace+0x12/0x14
> >>  [<c0105515>] dump_stack+0x15/0x17
> >>  [<c0114da7>] __might_sleep+0xb7/0xc9
> >>  [<c0451771>] mutex_lock+0x15/0x1f
> >>  [<c0141b75>] lookup_module_symbol_name+0x17/0xc0
> >>  [<c014272a>] lookup_symbol_name+0x3f/0x43
> >>  [<c013287e>] print_name_offset+0x1f/0x96
> >>  [<c01330f7>] timer_list_show+0x802/0xcbd
> >>  [<c01335be>] sysrq_timer_list_show+0xc/0xe
> >>  [<c02cc4a1>] sysrq_handle_show_timers+0x8/0xa
> >>  [<c02cc3ac>] __handle_sysrq+0x7b/0x115
> >>  [<c02cc466>] handle_sysrq+0x20/0x24
> >>  [<c02c69c1>] kbd_event+0x3a8/0x5c7
> >>  [<c0362f8f>] input_pass_event+0x8f/0x91
> >>  [<c0363e77>] input_handle_event+0x98/0x38d
> >>  [<c0364e6d>] input_event+0x54/0x67
> >>  [<c03682c2>] atkbd_interrupt+0x200/0x59e
> >>  [<c0360cd0>] serio_interrupt+0x7c/0x80
> >>  [<c0361965>] i8042_interrupt+0x17a/0x289
> >>  [<c0147a5d>] handle_IRQ_event+0x28/0x59
> >>  [<c01493ca>] handle_level_irq+0xad/0x10b
> >>  [<c0105a13>] do_IRQ+0x93/0xd0
> >>  [<c010441e>] common_interrupt+0x2e/0x34
> >>  [<df39d7e3>] rcu_read_delay+0x8/0x36 [rcutorture]
> >>  [<df39d99a>] rcu_torture_reader+0x6e/0x169 [rcutorture]
> >>  [<c012c11e>] kthread+0x36/0x58
> >>  [<c010451b>] kernel_thread_helper+0x7/0x1c
> >>  =======================
> > 
> > We seem to have made a mess in there.  timer_list_show() ends up calling
> > lookup_module_symbol_name(), which takes a mutex.  However print_symbol()
> > (which is called at oops time, interrupt time, etc) calls
> > module_address_lookup(), which is basically the same, only it doesn't take
> > the mutex.
> > 
> > I guess a quicky fix would be to switch
> > kernel/time/timer_list.c:print_name_offset() from
> > lookup_module_symbol_name() to module_address_lookup().  But we'd still
> > have a mess in there.
> > 
> > (adds ccs, runs away)
> 
> I don't think rcutorture matters for this bug. 

Maybe not but that's the only way I could trigger it (insmod rcutorture and sysrq+q).

Thanks,

	Mariusz
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