Re: [patch] Real-Time Preemption, -RT-2.6.9-rc4-mm1-U9

[Ingo Molnar]

* K.R. Foley <kr@xxxxxxxxxx> wrote:

> Oct 21 12:33:22 porky kernel: BUG: atomic counter underflow at:
> Oct 21 12:33:22 porky kernel:  [<c0254dd8>] qdisc_destroy+0x98/0xa0 (12)
> Oct 21 12:33:22 porky kernel:  [<c0254fed>] dev_shutdown+0x3d/0xa0 (16)
> Oct 21 12:33:22 porky kernel:  [<c024773b>] unregister_netdevice+0x13b/0x280 (28)
> Oct 21 12:33:22 porky netfs: Mounting other filesystems:  succeeded
> Oct 21 12:33:22 porky kernel:  [<c0112fb0>] mcount+0x14/0x18 (12)
> Oct 21 12:33:22 porky kernel:  [<e09a6160>] tulip_remove_one+0x0/0xa0 [tulip] (4)
> Oct 21 12:33:22 porky kernel:  [<c02058de>] unregister_netdev+0x1e/0x30 (24)
> Oct 21 12:33:22 porky kernel:  [<e09a618f>] tulip_remove_one+0x2f/0xa0 [tulip] (16)
> Oct 21 12:33:22 porky kernel:  [<c01f2907>] device_release_driver+0x67/0x70 (8)
> Oct 21 12:33:22 porky kernel:  [<c0112fb0>] mcount+0x14/0x18 (8)
> Oct 21 12:33:22 porky kernel:  [<c01c4e26>] pci_device_remove+0x76/0x80 (20)
> Oct 21 12:33:22 porky kernel:  [<c01f573b>] device_detach_shutdown+0xb/0x40 (12)
> Oct 21 12:33:22 porky kernel:  [<c01f2907>] device_release_driver+0x67/0x70 (12)
> Oct 21 12:33:22 porky kernel:  [<c01f293b>] driver_detach+0x2b/0x40 (24)
> Oct 21 12:33:22 porky kernel:  [<c01f2daf>] bus_remove_driver+0x3f/0x70 (20)
> Oct 21 12:33:22 porky kernel:  [<c01f32b9>] driver_unregister+0x19/0x30 (20)
> Oct 21 12:33:22 porky kernel:  [<c01c50cc>] pci_unregister_driver+0x1c/0x30 (16)
> Oct 21 12:33:22 porky kernel:  [<e09a7767>] tulip_cleanup+0x17/0x1b [tulip] (16)
> Oct 21 12:33:22 porky kernel:  [<c0139801>] sys_delete_module+0x121/0x150 (12)
> Oct 21 12:33:22 porky kernel:  [<c01531a1>] sys_munmap+0x51/0x60 (64)
> Oct 21 12:33:22 porky kernel:  [<c0116a20>] do_page_fault+0x0/0x660 (16)
> Oct 21 12:33:22 porky kernel:  [<c0106719>] sysenter_past_esp+0x52/0x71 (16)

i think this is an upstream bug that the atomic-counter debugging assert
triggers. Jeff, the assert above shows qdisc->refcnt underflowing from 0
to -1. So the qdisc_destroy() [or dev_shutdown()?] use is inbalanced. 
Plus rtl8139 is doing this too, see the log below. The upstream kernel
does not notice this condition. Or is ->refcnt allowed to underflow?

	Ingo

Oct 20 16:47:18 localhost kernel: BUG: atomic counter underflow at:
Oct 20 16:47:18 localhost kernel:  [<c02b8d88>] qdisc_destroy+0x98/0xa0 (12)
Oct 20 16:47:18 localhost kernel:  [<c02b8f9d>] dev_shutdown+0x3d/0xa0 (16)
Oct 20 16:47:18 localhost kernel:  [<c02aa38b>] unregister_netdevice+0x13b/0x280 (28)
Oct 20 16:47:18 localhost kernel:  [<c01148b0>] mcount+0x14/0x18 (8)
Oct 20 16:47:18 localhost kernel:  [<e0836b10>] rtl8139_remove_one+0x0/0xa0 [8139too] (4)
Oct 20 16:47:18 localhost kernel:  [<c0241f8e>] unregister_netdev+0x1e/0x30 (24)
Oct 20 16:47:18 localhost kernel:  [<e0836b3a>] rtl8139_remove_one+0x2a/0xa0 [8139too] (16)
Oct 20 16:47:18 localhost kernel:  [<c01148b0>] mcount+0x14/0x18 (12)
Oct 20 16:47:18 localhost kernel:  [<c01e4016>] pci_device_remove+0x76/0x80 (20)
Oct 20 16:47:18 localhost kernel:  [<c02306cb>] device_detach_shutdown+0xb/0x40 (12)
Oct 20 16:47:18 localhost kernel:  [<c022d817>] device_release_driver+0x67/0x70 (12)
Oct 20 16:47:18 localhost kernel:  [<c022d84b>] driver_detach+0x2b/0x40 (24)
Oct 20 16:47:18 localhost kernel:  [<c022dcbf>] bus_remove_driver+0x3f/0x70 (20)
Oct 20 16:47:18 localhost kernel:  [<c022e1c9>] driver_unregister+0x19/0x30 (20)
Oct 20 16:47:18 localhost kernel:  [<c01e42bc>] pci_unregister_driver+0x1c/0x30 (16)
Oct 20 16:47:18 localhost kernel:  [<e0838b07>] rtl8139_cleanup_module+0x17/0x1b [8139too] (16)
Oct 20 16:47:18 localhost kernel:  [<c013c8d1>] sys_delete_module+0x121/0x150 (12)
Oct 20 16:47:18 localhost kernel:  [<c01596a4>] sys_munmap+0x54/0x70 (64)
Oct 20 16:47:18 localhost kernel:  [<c0118560>] do_page_fault+0x0/0x6d0 (16)
Oct 20 16:47:18 localhost kernel:  [<c0107b49>] sysenter_past_esp+0x52/0x71 (16)
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