Re: BUG: sleeping function called from invalid context at mm/slub.c:793

["Kirill A. Shutemov" <kirill@shutemov.name>]

On Tue, Jan 11, 2011 at 12:29:41PM +0200, Avi Kivity wrote:
> On 01/11/2011 11:49 AM, Avi Kivity wrote:
> > On 01/10/2011 09:31 PM, Kirill A. Shutemov wrote:
> >> On Mon, Jan 10, 2011 at 10:52:05AM -0600, Christoph Lameter wrote:
> >> >
> >> >  On Mon, 10 Jan 2011, Kirill A. Shutemov wrote:
> >> >
> >> > >  Every time I run qemu with KVM enabled I get this in dmesg:
> >> > >
> >> > >  [  182.878328] BUG: sleeping function called from invalid 
> >> context at mm/slub.c:793
> >> > >  [  182.878339] in_atomic(): 1, irqs_disabled(): 0, pid: 4992, 
> >> name: qemu
> >> > >  [  182.878355] Pid: 4992, comm: qemu Not tainted 2.6.37+ #31
> >> > >  [  182.878361] Call Trace:
> >> > >  [  182.878381]  [<c104e317>] ? __might_sleep+0xd0/0xd7
> >> > >  [  182.878394]  [<c10ec337>] ? 
> >> slab_pre_alloc_hook.clone.39+0x23/0x27
> >> > >  [  182.878404]  [<c10ece27>] ? kmem_cache_alloc+0x22/0xc8
> >> > >  [  182.878414]  [<c1030221>] ? init_fpu+0x44/0x7b
> >> >
> >> >  fpu_alloc() does call kmem_cache_alloc with GFP_KERNEL although we 
> >> are in
> >> >  an atomic context.
> >>
> >> Something like this?
> >>
> >> ---
> >>  From 7c6fbfed72e7d22cbdf7393f9711d521e0fbb4a6 Mon Sep 17 00:00:00 2001
> >> From: Kirill A. Shutemov<kirill@shutemov.name>
> >> Date: Mon, 10 Jan 2011 21:24:23 +0200
> >> Subject: [PATCH] x86, fpu_alloc(): call kmem_cache_alloc() with 
> >> GFP_ATOMIC
> >>
> >> [  182.878328] BUG: sleeping function called from invalid context at 
> >> mm/slub.c:793
> >> [  182.878339] in_atomic(): 1, irqs_disabled(): 0, pid: 4992, name: qemu
> >> [  182.878355] Pid: 4992, comm: qemu Not tainted 2.6.37+ #31
> >> [  182.878361] Call Trace:
> >> [  182.878381]  [<c104e317>] ? __might_sleep+0xd0/0xd7
> >> [  182.878394]  [<c10ec337>] ? slab_pre_alloc_hook.clone.39+0x23/0x27
> >> [  182.878404]  [<c10ece27>] ? kmem_cache_alloc+0x22/0xc8
> >> [  182.878414]  [<c1030221>] ? init_fpu+0x44/0x7b
> >> [  182.878426]  [<c130cc29>] ? do_device_not_available+0x0/0x1b
> >> [  182.878435]  [<c1030221>] ? init_fpu+0x44/0x7b
> >> [  182.878444]  [<c102a588>] ? math_state_restore+0x24/0x47
> >> [  182.878453]  [<c130cc39>] ? do_device_not_available+0x10/0x1b
> >> [  182.878462]  [<c130c4ab>] ? error_code+0x67/0x6c
> >> [  182.878475]  [<c1012340>] ? kvm_load_guest_fpu+0xa1/0xaa
> >> [  182.878484]  [<c1013364>] ? kvm_arch_vcpu_ioctl_run+0x798/0xbe8
> >> [  182.878496]  [<c1004523>] ? kvm_vcpu_ioctl+0x105/0x46e
> >> [  182.878508]  [<c107dce0>] ? get_futex_key+0x73/0x132
> >> [  182.878517]  [<c107e352>] ? futex_wake+0xb6/0xc0
> >> [  182.878527]  [<c107f8d6>] ? do_futex+0x87/0x669
> >> [  182.878535]  [<c100441e>] ? kvm_vcpu_ioctl+0x0/0x46e
> >> [  182.878545]  [<c1101ebf>] ? do_vfs_ioctl+0x4a0/0x4d1
> >> [  182.878554]  [<c130e348>] ? do_page_fault+0x2eb/0x316
> >> [  182.878564]  [<c1101f36>] ? sys_ioctl+0x46/0x68
> >> [  182.878572]  [<c130bdc0>] ? syscall_call+0x7/0xb
> >> [  182.878585]  [<c1300000>] ? aer_probe+0x1da/0x274
> >>
> >> Signed-off-by: Kirill A. Shutemov<kirill@shutemov.name>
> >> ---
> >>   arch/x86/include/asm/i387.h |    2 +-
> >>   1 files changed, 1 insertions(+), 1 deletions(-)
> >>
> >> diff --git a/arch/x86/include/asm/i387.h b/arch/x86/include/asm/i387.h
> >> index ef32890..8b896dd 100644
> >> --- a/arch/x86/include/asm/i387.h
> >> +++ b/arch/x86/include/asm/i387.h
> >> @@ -426,7 +426,7 @@ static inline int fpu_alloc(struct fpu *fpu)
> >>   {
> >>       if (fpu_allocated(fpu))
> >>           return 0;
> >> -    fpu->state = kmem_cache_alloc(task_xstate_cachep, GFP_KERNEL);
> >> +    fpu->state = kmem_cache_alloc(task_xstate_cachep, GFP_ATOMIC);
> >>       if (!fpu->state)
> >>           return -ENOMEM;
> >>       WARN_ON((unsigned long)fpu->state&  15);
> >
> > If this fails, a task will be killed.  I'll patch kvm to ensure that 
> > the fpu is initialized.
> >
> 
> Please try out the attached patch.

It helps.

Reported-and-tested-by: Kirill A. Shutemov <kas@openvz.org>

Thanks.
> 
> -- 
> error compiling committee.c: too many arguments to function
> 

> From f3a6041b5bb3bf7c88f9694a66d7f34be2f78845 Mon Sep 17 00:00:00 2001
> From: Avi Kivity <avi@redhat.com>
> Date: Tue, 11 Jan 2011 12:15:54 +0200
> Subject: [PATCH] KVM: Initialize fpu state in preemptible context
> 
> init_fpu() (which is indirectly called by the fpu switching code) assumes
> it is in process context.  Rather than makeing init_fpu() use an atomic
> allocation, which can cause a task to be killed, make sure the fpu is
> already initialized when we enter the run loop.
> 
> Signed-off-by: Avi Kivity <avi@redhat.com>
> ---
>  arch/x86/kernel/i387.c |    1 +
>  arch/x86/kvm/x86.c     |    3 +++
>  2 files changed, 4 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
> index 58bb239..e60c38c 100644
> --- a/arch/x86/kernel/i387.c
> +++ b/arch/x86/kernel/i387.c
> @@ -169,6 +169,7 @@ int init_fpu(struct task_struct *tsk)
>  	set_stopped_child_used_math(tsk);
>  	return 0;
>  }
> +EXPORT_SYMBOL_GPL(init_fpu);
>  
>  /*
>   * The xstateregs_active() routine is the same as the fpregs_active() routine,
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 8652643..fd93cda 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -5351,6 +5351,9 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
>  	int r;
>  	sigset_t sigsaved;
>  
> +	if (!tsk_used_math(current) && init_fpu(current))
> +		return -ENOMEM;
> +
>  	if (vcpu->sigset_active)
>  		sigprocmask(SIG_SETMASK, &vcpu->sigset, &sigsaved);
>  
> -- 
> 1.7.1
> 


-- 
 Kirill A. Shutemov