Re: [crash, bisected] I2C, kobject (ffff81003e8c4160): tried toinit an initialized object

[Ingo Molnar]

* Ingo Molnar <mingo@xxxxxxx> wrote:

> found another bootup crash on an Athlon 64 X2 testsystem:
> 
> [   19.610000] bus: 'pci': add driver amd756_smbus
> [   19.615204] initcall amd756_init+0x0/0x20 returned 0 after 9 msecs
> [   19.620000] calling  amd756_s4882_init+0x0/0x2d7
> [   19.624242] ------------[ cut here ]------------
> [   19.628415] WARNING: at kernel/mutex.c:134 mutex_lock_nested+0xc0/0x267()
> [   19.630000] Pid: 1, comm: swapper Not tainted 2.6.26-tip #20066

> [   19.630000] ---[ end trace 0e79313125261797 ]---
> [   19.630000] BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
> [   19.630000] IP: [<ffffffff80861c66>] mutex_lock_nested+0x10d/0x267

turning off CONFIG_I2C_AMD756_S4882 works around this bug (as expected), 
via the patch below.

	Ingo

--------------------------->
commit 3f6403ab0bfdfca0cefbbc414afedc62734392f3
Author: Ingo Molnar <mingo@xxxxxxx>
Date:   Thu Jul 17 11:52:41 2008 +0200

    i2c: work around boot crash in amd756_s4882_init()
    
    work around:
    
    [   19.610000] bus: 'pci': add driver amd756_smbus
    [   19.615204] initcall amd756_init+0x0/0x20 returned 0 after 9 msecs
    [   19.620000] calling  amd756_s4882_init+0x0/0x2d7
    [   19.624242] ------------[ cut here ]------------
    [   19.628415] WARNING: at kernel/mutex.c:134 mutex_lock_nested+0xc0/0x267()
    [   19.630000] Pid: 1, comm: swapper Not tainted 2.6.26-tip #20066
    [   19.630000]
    [   19.630000] Call Trace:
    [   19.630000]  [<ffffffff802358f5>] warn_on_slowpath+0x58/0x7f
    [   19.630000]  [<ffffffff80263ac6>] ? ftrace_record_ip+0x20c/0x263
    [   19.630000]  [<ffffffff80514faa>] ? _raw_spin_unlock+0x8e/0x93
    [   19.630000]  [<ffffffff80507c44>] ? debug_locks_off+0x4/0x3c
    [   19.630000]  [<ffffffff80263ac6>] ? ftrace_record_ip+0x20c/0x263
    [   19.630000]  [<ffffffff8020b3a4>] ? mcount_call+0x5/0x31
    [   19.630000]  [<ffffffff80861c19>] mutex_lock_nested+0xc0/0x267
    [   19.630000]  [<ffffffff806e8ffd>] ? i2c_smbus_xfer+0x59/0x49c
    [   19.630000]  [<ffffffff80cc8575>] ? amd756_s4882_init+0x0/0x2d7
    [   19.630000]  [<ffffffff8020b3a4>] ? mcount_call+0x5/0x31
    [   19.630000]  [<ffffffff806e8ffd>] i2c_smbus_xfer+0x59/0x49c
    [   19.630000]  [<ffffffff80263ac6>] ? ftrace_record_ip+0x20c/0x263
    [   19.630000]  [<ffffffff80514faa>] ? _raw_spin_unlock+0x8e/0x93
    [   19.630000]  [<ffffffff80cc8584>] ? amd756_s4882_init+0xf/0x2d7
    [   19.630000]  [<ffffffff80263ac6>] ? ftrace_record_ip+0x20c/0x263
    [   19.630000]  [<ffffffff80cc8575>] ? amd756_s4882_init+0x0/0x2d7
    [   19.630000]  [<ffffffff8020b3a4>] ? mcount_call+0x5/0x31
    [   19.630000]  [<ffffffff80cc8575>] ? amd756_s4882_init+0x0/0x2d7
    [   19.630000]  [<ffffffff80cc85b6>] amd756_s4882_init+0x41/0x2d7
    [   19.630000]  [<ffffffff8024e325>] ? getnstimeofday+0x3f/0xa1
    [   19.630000]  [<ffffffff8024bf25>] ? ktime_get_ts+0x4e/0x53
    [   19.630000]  [<ffffffff80cc8575>] ? amd756_s4882_init+0x0/0x2d7
    [   19.630000]  [<ffffffff80ca49a0>] kernel_init+0x143/0x2a4
    [   19.630000]  [<ffffffff80863721>] ? _spin_unlock_irq+0x2b/0x37
    [   19.630000]  [<ffffffff8020c9f9>] child_rip+0xa/0x11
    [   19.630000]  [<ffffffff80ca485d>] ? kernel_init+0x0/0x2a4
    [   19.630000]  [<ffffffff8020c9ef>] ? child_rip+0x0/0x11
    [   19.630000]
    [   19.630000] ---[ end trace 0e79313125261797 ]---
    [   19.630000] BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
    [   19.630000] IP: [<ffffffff80861c66>] mutex_lock_nested+0x10d/0x267
    
    which occurs with:
    
      http://redhat.com/~mingo/misc/config-Thu_Jul_17_11_34_08_CEST_2008.bad
    
    Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
---
 drivers/i2c/busses/Kconfig |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index 2213fab..ead9209 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -56,6 +56,9 @@ config I2C_AMD756
 config I2C_AMD756_S4882
 	tristate "SMBus multiplexing on the Tyan S4882"
 	depends on I2C_AMD756 && EXPERIMENTAL
+	# broke an Athlon 64 X2 Asus A8N-E with:
+	# http://redhat.com/~mingo/misc/config-Thu_Jul_17_11_34_08_CEST_2008.bad
+	depends on 0
 	help
 	  Enabling this option will add specific SMBus support for the Tyan
 	  S4882 motherboard.  On this 4-CPU board, the SMBus is multiplexed
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