Message-ID: <386072610811040224u1545b110ida9de3f56a5ab9a7@mail.gmail.com>
Date:	Tue, 4 Nov 2008 18:24:07 +0800
From:	"Bryan Wu" <cooloney@...nel.org>
To:	"Lennert Buytenhek" <buytenh@...tstofly.org>
Cc:	netdev@...r.kernel.org, "Andy Fleming" <afleming@...escale.com>,
	"Byron Bradley" <byron.bbradley@...il.com>,
	"Tim Ellis" <tim.ellis@....com>, "Imre Kaloz" <kaloz@...nwrt.org>,
	"Nicolas Pitre" <nico@....org>, "Dirk Teurlings" <dirk@...xia.nl>,
	"Peter van Valderen" <p.v.valderen@...il.com>
Subject: Re: [BUG] rmmod bfin_mac netdev driver module will cause system crash.

On Tue, Nov 4, 2008 at 4:45 PM, Bryan Wu <cooloney@...nel.org> wrote:
> Hi Lennert,
>
> I got a regression since I update our blackfin kernel to the lastest
> 2.6.28-rc2 which includes your phylib patches.
> Please find the tracker here:
> https://blackfin.uclinux.org/gf/project/uclinux-dist/tracker/?action=TrackerItemEdit&tracker_id=141&tracker_item_id=4595
>
> Briefly, the calling chain is:
> in bfin_mac_remove(), mdiobus_unregister() ->
> device_unregister(&bus->dev); -> put_device() -> kobject_put() ->
> kref_put(&kobj->kref, kobject_release); -> kobject_release() ->
> kobject_cleanup() -> mdiobus_release().
> So in mdiobus_unregister() bus->state = MDIOBUS_UNREGISTERED; but in
> mdiobus_release(), this BUG_ON will fire:
> BUG_ON(bus->state != MDIOBUS_RELEASED);
>
> How about this patch?
>
> ---
> Index: drivers/net/phy/mdio_bus.c
> ===================================================================
> --- drivers/net/phy/mdio_bus.c  (revision 5575)
> +++ drivers/net/phy/mdio_bus.c  (working copy)
> @@ -134,13 +134,16 @@
>        int i;
>
>        BUG_ON(bus->state != MDIOBUS_REGISTERED);
> -       bus->state = MDIOBUS_UNREGISTERED;
>
> +       bus->state = MDIOBUS_RELEASED;
> +
>        device_unregister(&bus->dev);
>        for (i = 0; i < PHY_MAX_ADDR; i++) {
>                if (bus->phy_map[i])
>                        device_unregister(&bus->phy_map[i]->dev);
>        }
> +
> +       bus->state = MDIOBUS_UNREGISTERED;
>  }
>  EXPORT_SYMBOL(mdiobus_unregister);
> ---
>
> This regression is gone, but I'm not sure whether there is some side effect.
> Please review.
>
> Thanks a lot
> -Bryan
>

Oh, after applying this patch, I met a new WARN_ON issue:
---
root:/> rmmod bfin_mac
------------[ cut here ]------------
WARNING: at lib/kobject.c:593 _kobject_put+0x4e/0x58()
kobject: '<NULL>' (0098f6a4): is not initialized, yet kobject_put() is
being called.
Modules linked in: bfin_mac(-)
Hardware Trace:
   0 Target : <0x0000485c> { _dump_stack + 0x0 }
     Source : <0x0000e2fc> { _warn_slowpath + 0x58 } CALL pcrel
   1 Target : <0x0000e2fc> { _warn_slowpath + 0x58 }
     Source : <0x000294aa> { _print_modules + 0x7a } RTS
   2 Target : <0x000294a4> { _print_modules + 0x74 }
     Source : <0x0000e9b6> { _printk + 0x16 } RTS
   3 Target : <0x0000e9b2> { _printk + 0x12 }
     Source : <0x0000f1e8> { _vprintk + 0x130 } RTS
   4 Target : <0x0000f1c8> { _vprintk + 0x110 }
     Source : <0x0000f30c> { _vprintk + 0x254 } JUMP.S
   5 Target : <0x0000f30c> { _vprintk + 0x254 }
     Source : <0x0000e826> { _wake_up_klogd + 0x1a } RTS
   6 Target : <0x0000e826> { _wake_up_klogd + 0x1a }
     Source : <0x0000e818> { _wake_up_klogd + 0xc } IF !CC JUMP
   7 Target : <0x0000e80c> { _wake_up_klogd + 0x0 }
     Source : <0x0000ec40> { _release_console_sem + 0x1b0 } JUMP.L
   8 Target : <0x0000ec38> { _release_console_sem + 0x1a8 }
     Source : <0x0000ec2c> { _release_console_sem + 0x19c } IF !CC JUMP
   9 Target : <0x0000ec28> { _release_console_sem + 0x198 }
     Source : <0x0000ec1a> { _release_console_sem + 0x18a } IF !CC JUMP
  10 Target : <0x0000ec14> { _release_console_sem + 0x184 }
     Source : <0x00021de8> { _up + 0x3c } RTS
  11 Target : <0x00021de2> { _up + 0x36 }
     Source : <0x00021dd4> { _up + 0x28 } IF !CC JUMP
  12 Target : <0x00021dac> { _up + 0x0 }
     Source : <0x0000ec10> { _release_console_sem + 0x180 } CALL pcrel
  13 Target : <0x0000ebfc> { _release_console_sem + 0x16c }
     Source : <0x0000eae2> { _release_console_sem + 0x52 } IF !CC JUMP
  14 Target : <0x0000eab2> { _release_console_sem + 0x22 }
     Source : <0x0000ebde> { _release_console_sem + 0x14e } IF !CC JUMP
  15 Target : <0x0000ebd8> { _release_console_sem + 0x148 }
     Source : <0x0000e776> { __call_console_drivers + 0x7e } RTS
Stack info:
 SP: [0x00203cfc] <0x00203cfc> /* kernel dynamic memory */
 FP: (0x00203db4)
 Memory from 0x00203cf0 to 00204000
00203cf0: ffffff16  00203cfc  001725e4 [0000e2fc]<0000e300> 00203d1c
00142380  0016d044
00203d10: 00142380  00000251  00203d1c  626f6b5f  7463656a  7475705f
3478302b  78302f65
00203d30: 00003835  0098e190  00c63fb0  002e9e9c <0000eb62> 0016d068
0016d068  0016d040
00203d50:<0000ebd8><0000ec14> 000032ea  00203df8 <0008e546> 00162b74
0000e9a0  0000001f
00203d70: fffffff1  0016d070 <0000f30c> 00162b74  0000e9a0  00162b80
00000004  0000000f
00203d90: 10624dd3  0097d4c4  00c63fb0  000000d0  000000d0  00203e34
00203db0  0000ffff
00203db0: 00000000 (00000000)<00089f68><00089f7e> 0017b070  0017b070
001725e4  0017b070
00203dd0: 00000000 <0009f7fa> 0098f76c <0004da72> 037f5000  00c63f58
<0009f828> 0098f76c
00203df0: 0098f600  0017b008  002e9e9c  00203e20 <00089f16> 0098f6a4
00975800  000000ac
00203e10: 00000002  00000002  0000002e  00203e2c  00000000  0098f6a4
<0097cd34> 00975b80
00203e30: 00000002  00000001  0000001f <000a141a> 0016c084  0097def4
0016c130  00000068
00203e50: 00000001  00203e64 <000a14b6> 0016c084  0097def4 <000a08f2>
0097e000  0097def4
00203e70:<000a08f8> 0097e000  0097def4  00000000  00000880  002e9e9c
<00109720> 0000001f
00203e90:<0002a0e2> 0097e000  00000081  0000004c  001e9b94 <00043122>
0017be00  6e696662
00203eb0: 63616d5f  00000000  00000000  00000000  00000000  00000000
00000000  00000000
00203ed0: 00000000  00000000  00000000  00000000  00000000  00000000
0097e000  00000880
00203ef0: 00203ef4  00000000 <ffa008d4> 00029f80  00000081  00000000
ffffe000  0017c776
00203f10: 00c68de0  0015e23c  00000000  0000002e  00000002  002821ac
00008000  00000000
00203f30: 00000000  00204000  002821ac  002821ac <0029d3c2><ffa00e3c>
02002020  00192d99
00203f50: 0028cf9f  00192d92  0028cf96  00000000  0000000f  00000000
00000000  00000000
00203f70: 00000000  00000000  00000000  00000000  00000000  00000000
00000000  00000000
00203f90: 00000000  00000000  00000000  00000000  00000000  00000000
00000000  002d5f50
00203fb0: 002e9fe6  002e9e90  002e9e9c  00000001  002e9f80  0000004c
002e0664  002e0664
00203fd0: 00000081  00000880  00000000  00000002  0000002e  00000000
002e065c  00000880
00203ff0: 002e065c  002e065c  00000081  00000006  00000000
Return addresses in stack:
    address : <0x0000e2fc> { _warn_slowpath + 0x58 }
    address : <0x0000e300> { _warn_slowpath + 0x5c }
    address : <0x0000eb62> { _release_console_sem + 0xd2 }
    address : <0x0000ebd8> { _release_console_sem + 0x148 }
    address : <0x0000ec14> { _release_console_sem + 0x184 }
    address : <0x0008e546> { _vscnprintf + 0x16 }
    address : <0x0000f30c> { _vprintk + 0x254 }
   frame  1 : <0x00089f68> { _kobject_del + 0x10 }
    address : <0x00089f7e> { _kobject_del + 0x26 }
    address : <0x0009f7fa> { _device_del + 0x10a }
    address : <0x0004da72> { _ilookup5 + 0x2e }
    address : <0x0009f828> { _device_unregister + 0xc }
    address : <0x00089f16> { _kobject_put + 0x4e }
    address : <0x0097cd34> { :bfin_mac:_cleanup_module + 0x68 }
    address : <0x000a141a> { ___device_release_driver + 0x5e }
    address : <0x000a14b6> { _driver_detach + 0x72 }
    address : <0x000a08f2> { _bus_remove_driver + 0x6a }
    address : <0x000a08f8> { _bus_remove_driver + 0x70 }
    address : <0x00109720> { _mutex_lock_interruptible + 0xc }
    address : <0x0002a0e2> { _sys_delete_module + 0x162 }
    address : <0x00043122> { _free_bprm + 0x12 }
    address : <0xffa008d4> { _system_call + 0x68 }
    address : <0x0029d3c2> [ rmmod + 0x1d382 ]
    address : <0xffa00e3c> { _evt_system_call + 0x64 }
---[ end trace 96c9ba4ee8d1eb27 ]

This WARN was fired by this calling chain: mdiobus_unregister() ->
put_device() -> kobject_put();
IMO, mdiobus_release should be called after mdiobus_free, right. So my
patch is not a good way to solve this bug.
Any idea about this?

-Bryan
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