Re: early kernel crash when kmemleak is enabled

From: Marcin Slusarz
Date: Fri May 27 2011 - 16:25:22 EST

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:

[ 0.100045] BUG: unable to handle kernel NULL pointer dereference at (null)
[ 0.101303] IP: [<ffffffff810854d1>] __queue_work+0x29/0x41a
[ 0.102210] PGD 0
[ 0.102551] Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
[ 0.103459] last sysfs file:
[ 0.103949] CPU 0
[ 0.104260] Modules linked in:
[ 0.104803]
[ 0.105052] Pid: 1, comm: swapper Not tainted 2.6.39-rc4-nv+ #721 Bochs Bochs
[ 0.106193] RIP: 0010:[<ffffffff810854d1>] [<ffffffff810854d1>] __queue_work+0x29/0x41a
[ 0.107472] RSP: 0018:ffff880007c03c90 EFLAGS: 00010246
[ 0.108310] RAX: 0000000000000000 RBX: ffffffff81a4fa80 RCX: ffff880007c03bb0
[ 0.109423] RDX: 0000000000000003 RSI: ffffffff81e5ade8 RDI: 0000000000000001
[ 0.110000] RBP: ffff880007c03ce0 R08: ffffffff81e5ade0 R09: 000000000000005a
[ 0.110000] R10: ffffea0000000008 R11: 0000000000000000 R12: 0000000000000000
[ 0.110000] R13: 0000000000000000 R14: 0000000000000000 R15: ffff880007946480
[ 0.110000] FS: 0000000000000000(0000) GS:ffff880007c00000(0000) knlGS:0000000000000000
[ 0.110000] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[ 0.110000] CR2: 0000000000000000 CR3: 0000000001a23000 CR4: 00000000000006f0
[ 0.110000] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 0.110000] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[ 0.110000] Process swapper (pid: 1, threadinfo ffff880007ac2000, task ffff880007ac8000)
[ 0.110000] Stack:
[ 0.110000] 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[ 0.110000] 0000000000000000 0000000000000000 ffffffff81a4fa80 ffff880007946330
[ 0.110000] 0000000000000000 ffff880007946480 ffff880007c03cf0 ffffffff81085910
[ 0.110000] Call Trace:
[ 0.110000] <IRQ>
[ 0.110000] [<ffffffff81085910>] queue_work_on+0x16/0x1d
[ 0.110000] [<ffffffff81085abc>] queue_work+0x29/0x55
[ 0.110000] [<ffffffff81085afb>] schedule_work+0x13/0x15
[ 0.110000] [<ffffffff81242de1>] free_object+0x90/0x95
[ 0.110000] [<ffffffff81242f6d>] debug_check_no_obj_freed+0x187/0x1d3
[ 0.110000] [<ffffffff814b6504>] ? _raw_spin_unlock_irqrestore+0x30/0x4d
[ 0.110000] [<ffffffff8110bd14>] ? free_object_rcu+0x68/0x6d
[ 0.110000] [<ffffffff8110890c>] kmem_cache_free+0x64/0x12c
[ 0.110000] [<ffffffff8110bd14>] free_object_rcu+0x68/0x6d
[ 0.110000] [<ffffffff810b58bc>] __rcu_process_callbacks+0x1b6/0x2d9
[ 0.110000] [<ffffffff81095c9f>] ? tick_handle_periodic+0x1f/0x6c
[ 0.110000] [<ffffffff810b5a5a>] rcu_process_callbacks+0x7b/0x83
[ 0.110000] [<ffffffff810733b2>] __do_softirq+0x117/0x207
[ 0.110000] [<ffffffff810b05d3>] ? handle_irq_event+0x47/0x5c
[ 0.110000] [<ffffffff814bd0cc>] call_softirq+0x1c/0x30
[ 0.110000] [<ffffffff81034bc4>] do_softirq+0x38/0x80
[ 0.110000] [<ffffffff810730ed>] irq_exit+0x4e/0xa0
[ 0.110000] [<ffffffff8103429a>] do_IRQ+0x97/0xae
[ 0.110000] [<ffffffff814b6853>] common_interrupt+0x13/0x13
[ 0.110000] <EOI>
[ 0.110000] [<ffffffff8123d25f>] ? delay_tsc+0x48/0xcb
[ 0.110000] [<ffffffff8123d32a>] __const_udelay+0x25/0x27
[ 0.110000] [<ffffffff81aaae16>] timer_irq_works+0x3c/0x77
[ 0.110000] [<ffffffff81aab422>] setup_IO_APIC+0x337/0x755
[ 0.110000] [<ffffffff81aa956c>] native_smp_prepare_cpus+0x3a0/0x451
[ 0.110000] [<ffffffff814b64b9>] ? _raw_spin_unlock_irq+0x19/0x34
[ 0.110000] [<ffffffff81a9e52b>] kernel_init+0x4e/0x135
[ 0.110000] [<ffffffff8123e0fe>] ? trace_hardirqs_on_thunk+0x3a/0x3c
[ 0.110000] [<ffffffff814bcfd4>] kernel_thread_helper+0x4/0x10
[ 0.110000] [<ffffffff81063d70>] ? finish_task_switch+0x5a/0xcb
[ 0.110000] [<ffffffff814b64b9>] ? _raw_spin_unlock_irq+0x19/0x34
[ 0.110000] [<ffffffff814b68b1>] ? retint_restore_args+0xe/0xe
[ 0.110000] [<ffffffff81a9e4dd>] ? parse_early_options+0x20/0x20
[ 0.110000] [<ffffffff814bcfd0>] ? gs_change+0xb/0xb
[ 0.110000] 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
[ 0.110000] f6 45 00 40 0f 84 6b 01 00 00 b8 09 00 00 00 83 3d 28 10 a0
[ 0.110000] RIP [<ffffffff810854d1>] __queue_work+0x29/0x41a
[ 0.110000] RSP <ffff880007c03c90>
[ 0.110000] CR2: 0000000000000000
[ 0.110005] ---[ end trace 4eaa2a86a8e2da22 ]---
[ 0.110766] Kernel panic - not syncing: Fatal exception in interrupt


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--;

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