Hi Herton,

I got the below oops in Linux 3.7-rc4 and it's bisected down to

commit b54e1f88897bcacc2cd359f48ea3b39eaf55f084
Author: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com>
Date:   Mon Aug 27 20:56:51 2012 -0300

    floppy: don't call alloc_ordered_workqueue inside the alloc_disk loop


[   14.108013] CPU 0 
[   14.108013] Pid: 6, comm: kworker/u:0 Not tainted 3.7.0-rc4 #1 Bochs Bochs
[   14.108013] RIP: 0010:[<ffffffff8134eef5>]  [<ffffffff8134eef5>] blk_peek_request+0xd5/0x1c0
[   14.108013] RSP: 0000:ffff88000dc7dd88  EFLAGS: 00010092
[   14.108013] RAX: 0000000000000001 RBX: 0000000000000000 RCX: 0000000000000000
[   14.108013] RDX: ffff88000f602688 RSI: ffffffff81fd95d8 RDI: 6b6b6b6b6b6b6b6b
[   14.108013] RBP: ffff88000dc7dd98 R08: ffffffff81fd95c8 R09: 0000000000000000
[   14.108013] R10: ffffffff81fd9480 R11: 0000000000000001 R12: 6b6b6b6b6b6b6b6b
[   14.108013] R13: ffff88000dc7dfd8 R14: ffff88000dc7dfd8 R15: 0000000000000000
[   14.108013] FS:  0000000000000000(0000) GS:ffffffff81e21000(0000) knlGS:0000000000000000
[   14.108013] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[   14.108013] CR2: 0000000000000000 CR3: 0000000001e11000 CR4: 00000000000006f0
[   14.108013] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[   14.108013] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[   14.108013] Process kworker/u:0 (pid: 6, threadinfo ffff88000dc7c000, task ffff88000dc5ecc0)
[   14.108013] Stack:
[   14.108013]  0000000000000000 0000000000000000 ffff88000dc7ddb8 ffffffff8134efee
[   14.108013]  ffff88000dc7ddb8 0000000000000000 ffff88000dc7dde8 ffffffff814aef3c
[   14.108013]  ffffffff81e75d80 ffff88000dc0c640 ffff88000fbfb000 ffffffff814aed90
[   14.108013] Call Trace:
[   14.108013]  [<ffffffff8134efee>] blk_fetch_request+0xe/0x30
[   14.108013]  [<ffffffff814aef3c>] redo_fd_request+0x1ac/0x400
[   14.108013]  [<ffffffff814aed90>] ? start_motor+0x130/0x130
[   14.108013]  [<ffffffff8106b526>] process_one_work+0x136/0x450
[   14.108013]  [<ffffffff8106af65>] ? manage_workers+0x205/0x2e0
[   14.108013]  [<ffffffff8106bb6d>] worker_thread+0x14d/0x420
[   14.108013]  [<ffffffff8106ba20>] ? rescuer_thread+0x1a0/0x1a0
[   14.108013]  [<ffffffff8107075a>] kthread+0xba/0xc0
[   14.108013]  [<ffffffff810706a0>] ? __kthread_parkme+0x80/0x80
[   14.108013]  [<ffffffff818b553a>] ret_from_fork+0x7a/0xb0
[   14.108013]  [<ffffffff810706a0>] ? __kthread_parkme+0x80/0x80
[   14.108013] Code: 0f 84 c0 00 00 00 83 f8 01 0f 85 e2 00 00 00 81 4b 40 00 00 80 00 48 89 df e8 58 f8 ff ff be fb ff ff ff 48 89 df e8 fb fe ff ff <49> 8b 1c 24 49 39 dc 0f 85 2e ff ff ff 41 0f b6 84 24 28 04 00 
[   14.108013] RIP  [<ffffffff8134eef5>] blk_peek_request+0xd5/0x1c0
[   14.108013]  RSP <ffff88000dc7dd88>

Thanks,
Fengguang