Re: pci_get_subsys: GFP_KERNEL allocations with IRQs disabled

[Fengguang Wu]

On Wed, Aug 22, 2012 at 03:49:08PM +0800, Tang, Feng wrote:
> Hi Fengguang,
> 
> 
> On Wed, 22 Aug 2012 10:50:08 +0800
> Fengguang Wu <fengguang.wu@xxxxxxxxx> wrote:
> 
> > Feng,
> > 
> > > I think it's pci_get_subsys() triggered this assert:
> > > 
> > >         /*
> > >          * Oi! Can't be having __GFP_FS allocations with IRQs disabled.
> > >          */
> > >         if (DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags)))
> > >                 return;
> > 
> > It's bisected down to this commit:
> > 
> > commit 55c844a4dd16a4d1fdc0cf2a283ec631a02ec448
> > Author:     Feng Tang <feng.tang@xxxxxxxxx>
> > AuthorDate: Wed May 30 23:15:41 2012 +0800
> > Commit:     Ingo Molnar <mingo@xxxxxxxxxx>
> > CommitDate: Wed Jun 6 12:03:23 2012 +0200
> > 
> >     x86/reboot: Fix a warning message triggered by stop_other_cpus()
> > 
> > Thanks,
> > Fengguang
> 
> Thanks for the bisection.
> 
> Revert my commit should be a solution, but can we simply make the pci_device_id
> a local on stack one instead of using sleepable kmalloc for it, as this
> sounds fragile when pci_get_subsys get called in a late system reboot stage?

Good idea! I like this simple solution. It will sure fix the warning.

Reviewed-by: Fengguang Wu <fengguang.wu@xxxxxxxxx>

Thanks,
Fengguang

> ------------
> diff --git a/drivers/pci/search.c b/drivers/pci/search.c
> index 993d4a0..e5ccede 100644
> --- a/drivers/pci/search.c
> +++ b/drivers/pci/search.c
> @@ -246,7 +246,7 @@ struct pci_dev *pci_get_subsys(unsigned int vendor, unsigned int device,
>  			       struct pci_dev *from)
>  {
>  	struct pci_dev *pdev;
> -	struct pci_device_id *id;
> +	struct pci_device_id id;
>  
>  	/*
>  	 * pci_find_subsys() can be called on the ide_setup() path,
> @@ -257,17 +257,12 @@ struct pci_dev *pci_get_subsys(unsigned int vendor, unsigned int device,
>  	if (unlikely(no_pci_devices()))
>  		return NULL;
>  
> -	id = kzalloc(sizeof(*id), GFP_KERNEL);
> -	if (!id)
> -		return NULL;
> -	id->vendor = vendor;
> -	id->device = device;
> -	id->subvendor = ss_vendor;
> -	id->subdevice = ss_device;
> -
> -	pdev = pci_get_dev_by_id(id, from);
> -	kfree(id);
> +	id.vendor = vendor;
> +	id.device = device;
> +	id.subvendor = ss_vendor;
> +	id.subdevice = ss_device;
>  
> +	pdev = pci_get_dev_by_id(&id, from);
>  	return pdev;
>  }
>  
> 
> 
> > 
> > > [   91.282131] machine restart
> > > [   91.283895] ------------[ cut here ]------------
> > > [   91.284731] WARNING: at /c/wfg/linux/kernel/lockdep.c:2739 lockdep_trace_alloc+0x1fb/0x210()
> > > [   91.286132] Modules linked in:
> > > [   91.286703] Pid: 697, comm: reboot Not tainted 3.5.0-00024-g01ff5db-dirty #4
> > > [   91.287859] Call Trace:
> > > [   91.288289]  [<81050148>] warn_slowpath_common+0xb8/0x100
> > > [   91.289338]  [<8110acdb>] ? lockdep_trace_alloc+0x1fb/0x210
> > > [   91.290264]  [<8110acdb>] ? lockdep_trace_alloc+0x1fb/0x210
> > > [   91.291161]  [<810501ce>] warn_slowpath_null+0x3e/0x50
> > > [   91.292042]  [<8110acdb>] lockdep_trace_alloc+0x1fb/0x210
> > > [   91.292934]  [<81228e25>] kmem_cache_alloc_trace+0x55/0x600
> > > [   91.292934]  [<813025ca>] ? kobject_put+0x9a/0x160
> > > [   91.292934]  [<814e95e0>] ? klist_iter_exit+0x30/0x50
> > > [   91.292934]  [<81405881>] ? bus_find_device+0xf1/0x120
> > > [   91.292934]  [<81361a3c>] ? pci_get_subsys+0x11c/0x1b0
> > > [   91.292934]  [<81361a3c>] pci_get_subsys+0x11c/0x1b0
> > > [   91.292934]  [<81361afe>] pci_get_device+0x2e/0x40
> > > [   91.292934]  [<81033e25>] mach_reboot_fixups+0xa5/0xd0
> > > [   91.292934]  [<81027611>] native_machine_emergency_restart+0x1f1/0x590
> > > [   91.292934]  [<814f2e00>] ? printk+0x4b/0x5b
> > > [   91.292934]  [<810269ef>] native_machine_restart+0x6f/0x80
> > > [   91.292934]  [<810271cc>] machine_restart+0x1c/0x30
> > > [   91.292934]  [<810886e0>] kernel_restart+0x70/0xc0
> > > [   91.292934]  [<81088a85>] sys_reboot+0x325/0x380
> > > [   91.292934]  [<811f796c>] ? handle_pte_fault+0xdc/0x1740
> > > [   91.292934]  [<811f93e7>] ? handle_mm_fault+0x417/0x4a0
> > > [   91.292934]  [<8103e07b>] ? do_page_fault+0x7fb/0xb30
> > > [   91.292934]  [<810b33e7>] ? up_read+0x37/0x70
> > > [   91.292934]  [<8103e07b>] ? do_page_fault+0x7fb/0xb30
> > > [   91.292934]  [<8123c063>] ? do_sys_open+0x3a3/0x3f0
> > > [   91.292934]  [<8123c063>] ? do_sys_open+0x3a3/0x3f0
> > > [   91.292934]  [<810b0270>] ? update_rmtp+0xe0/0xe0
> > > [   91.292934]  [<8150376e>] ? restore_all+0xf/0xf
> > > [   91.292934]  [<8103d880>] ? vmalloc_sync_all+0x320/0x320
> > > [   91.292934]  [<81109fca>] ? trace_hardirqs_on_caller+0x28a/0x380
> > > [   91.292934]  [<81311594>] ? trace_hardirqs_on_thunk+0xc/0x10
> > > [   91.292934]  [<81503735>] syscall_call+0x7/0xb
> > > 
> > > Thanks,
> > > Fengguang
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