Re: [PATCH 2.6.20-rc1 00/10] Kernel memory leak detector 0.13

From: Catalin Marinas
Date: Wed Dec 27 2006 - 11:15:13 EST

On 17/12/06, Ingo Molnar <mingo@xxxxxxx> wrote:
it would be nice to record 1) the jiffies value at the time of
allocation, 2) the PID and the comm of the task that did the allocation.
The jiffies timestamp would be useful to see the age of the allocation,
and the PID/comm is useful for context.

Trying to copy the comm with get_task_comm, I get the lockdep report
below, caused by acquiring the task's alloc_lock. Any idea how to go
around this?

[ INFO: inconsistent lock state ]
2.6.20-rc2 #211
inconsistent {hardirq-on-W} -> {in-hardirq-W} usage.
swapper/0 [HC1[1]:SC0[0]:HE0:SE1] takes:
(init_task.alloc_lock){+-..}, at: [<c007d950>] get_task_comm+0x24/0x40
{hardirq-on-W} state was registered at:
[<c00493d0>] lock_acquire+0x80/0x94
[<c020cf1c>] _spin_lock+0x30/0x40
[<c0027c80>] copy_process+0x8b8/0x1208
[<c0028874>] do_fork+0xc0/0x1e0
[<c001497c>] kernel_thread+0x70/0x80
[<c000f864>] rest_init+0x1c/0x30
[<c000fa9c>] start_kernel+0x224/0x27c
[<00008078>] 0x8078
irq event stamp: 33758
hardirqs last enabled at (33757): [<c0014ef8>] default_idle+0x44/0x50
hardirqs last disabled at (33758): [<c00131d4>] __irq_svc+0x34/0xc0
softirqs last enabled at (33750): [<c002f97c>] __do_softirq+0x10c/0x124
softirqs last disabled at (33745): [<c002fde0>] irq_exit+0x58/0x60

other info that might help us debug this:
1 lock held by swapper/0:
#0: (&lp->lock){+...}, at: [<c0146b9c>] smc_interrupt+0x28/0x784

stack backtrace:
[<c0018cf4>] (dump_stack+0x0/0x14) from [<c00471b4>]
[<c0047098>] (print_usage_bug+0x0/0x154) from [<c0047b60>]
r8 = 00000001 r7 = C02A4348 r6 = 00000000 r5 = 00000002
r4 = C02A4638
[<c0047a80>] (mark_lock+0x0/0x4c8) from [<c0048b34>]
[<c0048710>] (__lock_acquire+0x0/0xc40) from [<c00493d0>]
[<c0049350>] (lock_acquire+0x0/0x94) from [<c020cf1c>] (_spin_lock+0x30/0x40)
[<c020ceec>] (_spin_lock+0x0/0x40) from [<c007d950>] (get_task_comm+0x24/0x40)
r4 = C02A4348
[<c007d92c>] (get_task_comm+0x0/0x40) from [<c0075570>]
r6 = C7596E60 r5 = A0000193 r4 = C7596E64
[<c0075408>] (memleak_alloc+0x0/0x2b4) from [<c0072800>]
[<c00726f0>] (kmem_cache_alloc+0x0/0x124) from [<c0199228>]
[<c01991f4>] (__alloc_skb+0x0/0x130) from [<c0146f04>]
[<c0146b74>] (smc_interrupt+0x0/0x784) from [<c005322c>]
[<c0053200>] (handle_IRQ_event+0x0/0x68) from [<c0054d94>]
r7 = C02A1128 r6 = C7805C20 r5 = 00000029 r4 = C02A1100
[<c0054cb0>] (handle_level_irq+0x0/0x150) from [<c001469c>]
r7 = 00008000 r6 = 00000029 r5 = 00000000 r4 = C029E000
[<c001462c>] (asm_do_IRQ+0x0/0x9c) from [<c00131d4>] (__irq_svc+0x34/0xc0)
r5 = FF000100 r4 = FFFFFFFF
[<c0014eb4>] (default_idle+0x0/0x50) from [<c0014cb0>] (cpu_idle+0x30/0x4c)
[<c0014c80>] (cpu_idle+0x0/0x4c) from [<c000f870>] (rest_init+0x28/0x30)
r5 = C02C3D30 r4 = C04DB2A4
[<c000f848>] (rest_init+0x0/0x30) from [<c000fa9c>] (start_kernel+0x224/0x27c)
[<c000f878>] (start_kernel+0x0/0x27c) from [<00008078>] (0x8078)

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