[PATCH] debugobjects: fix boot crash when both kmemleak anddebugobjects are enabled (was: Re: early kernel crash when kmemleak isenabled)

From: Marcin Slusarz
Date: Sat May 28 2011 - 07:23:58 EST

On Fri, May 27, 2011 at 10:37:54PM +0200, Thomas Gleixner wrote:
> On Fri, 27 May 2011, Marcin Slusarz wrote:
> > On Thu, May 19, 2011 at 03:08:53PM +0100, Catalin Marinas wrote:
> > > On Thu, 2011-05-19 at 14:54 +0100, Tejun Heo wrote:
> > > > On Thu, May 19, 2011 at 02:48:44PM +0100, Catalin Marinas wrote:
> > > > > Thanks for tracking this down. Untested (I can add a log afterwards):
> > > > >
> > > > > diff --git a/init/main.c b/init/main.c
> > > > > index 4a9479e..48df882 100644
> > > > > --- a/init/main.c
> > > > > +++ b/init/main.c
> > > > > @@ -580,8 +580,8 @@ asmlinkage void __init start_kernel(void)
> > > > > #endif
> > > > > page_cgroup_init();
> > > > > enable_debug_pagealloc();
> > > > > - kmemleak_init();
> > > > > debug_objects_mem_init();
> > > > > + kmemleak_init();
> > > > > setup_per_cpu_pageset();
> > > > > numa_policy_init();
> > > > > if (late_time_init)
> > > >
> > > > Heh, that was swift. Yeap, seems to work here. Please feel free to
> > > > add my Tested-by.
> > >
> > > Thanks. I have two other minor kmemleak fixes, so I'll send Linus a pull
> > > request in the next day or so.
> > >
> >
> > With this patch applied kernel didn't panic, but kmemleak did not work either:
> >
> > kmemleak: Early log buffer exceeded, please increase DEBUG_KMEMLEAK_EARLY_LOG_SIZE
> > kmemleak: Kernel memory leak detector disabled
> >
> > I increased DEBUG_KMEMLEAK_EARLY_LOG_SIZE from 400 to 1000, and it crashed in
> > exactly the same way:
>
> ...
>
> > The problem is: debugobjects want to use workqueues (system_wq actually), but they
> > are initialized much later in a boot process.
> >
> > Attached patch fixes this issue for me.
> >
> >
> > diff --git a/lib/debugobjects.c b/lib/debugobjects.c
> > index 9d86e45..a78b7c6 100644
> > --- a/lib/debugobjects.c
> > +++ b/lib/debugobjects.c
> > @@ -198,7 +198,7 @@ static void free_object(struct debug_obj *obj)
> > * initialized:
> > */
> > if (obj_pool_free > ODEBUG_POOL_SIZE && obj_cache)
> > - sched = !work_pending(&debug_obj_work);
> > + sched = keventd_up() && !work_pending(&debug_obj_work);
> > hlist_add_head(&obj->node, &obj_pool);
> > obj_pool_free++;
> > obj_pool_used--;
> >
>
> Sigh, yes. Care to resend with changelog and signed-off-by ?
>

Sure.

---
From: Marcin Slusarz <marcin.slusarz@xxxxxxxxx>
Subject: [PATCH] debugobjects: fix boot crash when both kmemleak and debugobjects are enabled

order of initialization look like this:

...
debugobjects
kmemleak
...(lots of other subsystems)...
workqueues (through early initcall)
...

debugobjects use schedule_work for batch freeing of its data and kmemleak
heavily use debugobjects, so when it comes to freeing and workqueues were
not initialized yet, kernel crashes:

BUG: unable to handle kernel NULL pointer dereference at (null)
IP: [<ffffffff810854d1>] __queue_work+0x29/0x41a
PGD 0
Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
(...)
Pid: 1, comm: swapper Not tainted 2.6.39-rc4-nv+ #721 Bochs Bochs
RIP: 0010:[<ffffffff810854d1>] [<ffffffff810854d1>] __queue_work+0x29/0x41a
(...)
Call Trace:
<IRQ>
[<ffffffff81085910>] queue_work_on+0x16/0x1d
[<ffffffff81085abc>] queue_work+0x29/0x55
[<ffffffff81085afb>] schedule_work+0x13/0x15
[<ffffffff81242de1>] free_object+0x90/0x95
[<ffffffff81242f6d>] debug_check_no_obj_freed+0x187/0x1d3
[<ffffffff814b6504>] ? _raw_spin_unlock_irqrestore+0x30/0x4d
[<ffffffff8110bd14>] ? free_object_rcu+0x68/0x6d
[<ffffffff8110890c>] kmem_cache_free+0x64/0x12c
[<ffffffff8110bd14>] free_object_rcu+0x68/0x6d
[<ffffffff810b58bc>] __rcu_process_callbacks+0x1b6/0x2d9
[<ffffffff81095c9f>] ? tick_handle_periodic+0x1f/0x6c
[<ffffffff810b5a5a>] rcu_process_callbacks+0x7b/0x83
[<ffffffff810733b2>] __do_softirq+0x117/0x207
[<ffffffff810b05d3>] ? handle_irq_event+0x47/0x5c
[<ffffffff814bd0cc>] call_softirq+0x1c/0x30
[<ffffffff81034bc4>] do_softirq+0x38/0x80
[<ffffffff810730ed>] irq_exit+0x4e/0xa0
[<ffffffff8103429a>] do_IRQ+0x97/0xae
[<ffffffff814b6853>] common_interrupt+0x13/0x13
<EOI>
[<ffffffff8123d25f>] ? delay_tsc+0x48/0xcb
[<ffffffff8123d32a>] __const_udelay+0x25/0x27
[<ffffffff81aaae16>] timer_irq_works+0x3c/0x77
[<ffffffff81aab422>] setup_IO_APIC+0x337/0x755
[<ffffffff81aa956c>] native_smp_prepare_cpus+0x3a0/0x451
[<ffffffff814b64b9>] ? _raw_spin_unlock_irq+0x19/0x34
[<ffffffff81a9e52b>] kernel_init+0x4e/0x135
[<ffffffff8123e0fe>] ? trace_hardirqs_on_thunk+0x3a/0x3c
[<ffffffff814bcfd4>] kernel_thread_helper+0x4/0x10
[<ffffffff81063d70>] ? finish_task_switch+0x5a/0xcb
[<ffffffff814b64b9>] ? _raw_spin_unlock_irq+0x19/0x34
[<ffffffff814b68b1>] ? retint_restore_args+0xe/0xe
[<ffffffff81a9e4dd>] ? parse_early_options+0x20/0x20
[<ffffffff814bcfd0>] ? gs_change+0xb/0xb
Code: c9 c3 55 48 89 e5 41 57 41 56 41 55 49 89 f5 41 54 48 c7 c6 a0 b7 a3 81 53 41 89 fc 48 83 ec 28 48 89 d3 48 89 d7 e8 63 d7 1b 00
f6 45 00 40 0f 84 6b 01 00 00 b8 09 00 00 00 83 3d 28 10 a0
RIP [<ffffffff810854d1>] __queue_work+0x29/0x41a
RSP <ffff880007c03c90>
CR2: 0000000000000000
---[ end trace 4eaa2a86a8e2da22 ]---
Kernel panic - not syncing: Fatal exception in interrupt

...because system_wq is NULL.

Fix it by checking if workqueues susbystem was initialized before using.

Signed-off-by: Marcin Slusarz <marcin.slusarz@xxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: stable@xxxxxxxxxx
---
lib/debugobjects.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/lib/debugobjects.c b/lib/debugobjects.c
index 9d86e45..a78b7c6 100644
--- a/lib/debugobjects.c
+++ b/lib/debugobjects.c
@@ -198,7 +198,7 @@ static void free_object(struct debug_obj *obj)
* initialized:
*/
if (obj_pool_free > ODEBUG_POOL_SIZE && obj_cache)
- sched = !work_pending(&debug_obj_work);
+ sched = keventd_up() && !work_pending(&debug_obj_work);
hlist_add_head(&obj->node, &obj_pool);
obj_pool_free++;
obj_pool_used--;
--
1.7.4.1
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