Re: [ANNOUNCE] 2.6.33.1-rt11 - BUG?

[Xianghua Xiao]

Here is the new dmesg output:
BUG: sleeping function called from invalid context at kernel/rtmutex.c:684
pcnt: 1 0 in_atomic(): 1, irqs_disabled(): 1, pid: 5770, name: insmod
Call Trace:
[ce935dc0] [c00096cc] show_stack+0x6c/0x1a4 (unreliable)
[ce935df0] [c001f928] __might_sleep+0x104/0x108
[ce935e00] [c03cb414] rt_spin_lock+0xa0/0xa4
[ce935e10] [c00a4098] kmem_cache_alloc+0x50/0x17c
[ce935e40] [c0073570] irq_to_desc_alloc_node+0x104/0x5ec
[ce935e60] [c00064e0] irq_setup_virq+0x30/0xa8
[ce935e80] [c000665c] irq_create_mapping+0x104/0x168
[ce935ea0] [d1f69bc4] dma_init+0x118/0x1f0 [ipc]
[ce935ee0] [d1f75018] ipc_init+0x18/0x140 [ipc]
[ce935ef0] [c00038e0] do_one_initcall+0x54/0x210
[ce935f20] [c005e424] sys_init_module+0x120/0x240
[ce935f40] [c00139d4] ret_from_syscall+0x0/0x38

I chased from ipc_init to irq_to_desc_alloc_node and found no
interrupt-disabling.

By looking at irq_to_desc_alloc_node (kernel/irq/handler.c) it has
raw_spin_lock_irqsave(), with this raw spinlock irqsave I'm not sure
if it causes trouble at kmem_cache_alloc after rt11 is applied, still
checking on that.

thanks,
xianghua

On Thu, Apr 1, 2010 at 12:46 PM, Xianghua Xiao <xiaoxianghua@xxxxxxxxx> wrote:
> That fixed it. Thanks!
> However I'm seeing two more similar rtmutex:684 BUGs from dmesg now,
> they're from my own drivers and I'm tracking them down.
>
> Xianghua
>
>
> On Thu, Apr 1, 2010 at 1:23 PM, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
>> On Thu, 1 Apr 2010, Xianghua Xiao wrote:
>>
>>> I'm testing 2.6.33.1 on ppc 834x with rt11 patch. After system is up I keep
>>> seeing this same message from dmesg:
>>>
>>> BUG: sleeping function called from invalid context at kernel/rtmutex.c:684
>>> pcnt: 0 0 in_atomic(): 0, irqs_disabled(): 1, pid: 16, name: events/0
>>> Call Trace:
>>> [cf85be80] [c00096cc] show_stack+0x6c/0x1a4 (unreliable)
>>> [cf85beb0] [c001f928] __might_sleep+0x104/0x108
>>> [cf85bec0] [c03cb444] rt_spin_lock+0xa0/0xa4
>>> [cf85bed0] [c0270b6c] lock_tx_qs+0x40/0x68
>>> [cf85bef0] [c02712cc] adjust_link+0x4c/0x240
>>> [cf85bf20] [c026d5ec] phy_state_machine+0x3bc/0x628
>>> [cf85bf40] [c003e69c] worker_thread+0x148/0x1f0
>>> [cf85bfa0] [c0042ec0] kthread+0x84/0x88
>>> [cf85bff0] [c00137f8] kernel_thread+0x4c/0x68
>>> BUG: sleeping function called from invalid context at kernel/rtmutex.c:684
>>> pcnt: 0 0 in_atomic(): 0, irqs_disabled(): 1, pid: 16, name: events/0
>>>
>>> #uname -a
>>> Linux 2.6.33.1-rt11 #3 PREEMPT RT Thu Apr 1 11:58:25 CDT 2010 ppc unknown
>>>
>>> This does not hang/lock the system yet...google reported similar 'bug' on
>>> older kernels. Is this a bug from 2.6.33.1-rt11 patch or I have to change
>>> phy.c somehow to avoid it? This traces back to a mutex lock in phy.c.
>>
>> No, it traces back to a call to lock_tx_qs() which is a spinlock in
>> mainline and gets converted to a "sleeping" spinlock in -RT. That
>> means it can't be called with interrupts disabled. But the code in
>> adjust_link does exaclty that.
>>
>> Does the patch below fix it ?
>>
>> Thanks,
>>
>> Â Â Â Âtglx
>> ---
>> Subject: net-gianfar-fix-rt-splat.patch
>> From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
>> Date: Thu, 01 Apr 2010 20:20:57 +0200
>>
>> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
>> ---
>> Âdrivers/net/gianfar.c | Â Â4 ++--
>> Â1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> Index: linux-2.6-tip/drivers/net/gianfar.c
>> ===================================================================
>> --- linux-2.6-tip.orig/drivers/net/gianfar.c
>> +++ linux-2.6-tip/drivers/net/gianfar.c
>> @@ -2717,7 +2717,7 @@ static void adjust_link(struct net_devic
>> Â Â Â Âstruct phy_device *phydev = priv->phydev;
>> Â Â Â Âint new_state = 0;
>>
>> - Â Â Â local_irq_save(flags);
>> + Â Â Â local_irq_save_nort(flags);
>> Â Â Â Âlock_tx_qs(priv);
>>
>> Â Â Â Âif (phydev->link) {
>> @@ -2785,7 +2785,7 @@ static void adjust_link(struct net_devic
>> Â Â Â Âif (new_state && netif_msg_link(priv))
>> Â Â Â Â Â Â Â Âphy_print_status(phydev);
>> Â Â Â Âunlock_tx_qs(priv);
>> - Â Â Â local_irq_restore(flags);
>> + Â Â Â local_irq_restore_nort(flags);
>> Â}
>>
>> Â/* Update the hash table based on the current list of multicast
>>
>>
>>
>>
>>
>
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