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From: Avi Kivity <avi@redhat.com>
To: Amit Shah <amshah@redhat.com>
Cc: Sheng Yang <sheng@linux.intel.com>,
	Marcelo Tosatti <mtosatti@redhat.com>,
	kvm@vger.kernel.org, Amit Shah <amit.shah@redhat.com>,
	"Han, Weidong" <weidong.han@intel.com>
Subject: Re: [PATCH 15/15] KVM: Fix racy in kvm_free_assigned_irq
Date: Mon, 29 Dec 2008 15:20:09 +0200	[thread overview]
Message-ID: <4958CE89.4050600@redhat.com> (raw)
In-Reply-To: <20081229054222.GB13166@shell.devel.redhat.com>

Amit Shah wrote:
> I see from the call chain kvm_put_kvm->...->kvm_arch_destroy_vm, no locks are 
> taken to actually destroy the vm. We can't be in ioctls, sure. But shouldn't 
> the mutex be taken to ensure there's nothing else going on while destroying?
>
>   

Locks are useless to guard against something happening concurrent with 
destruction, since we're about to destroy the lock.

> At least with the workqueue model, we could be called asynchronously in kernel 
> context and I would have held the mutex and about to inject interrupts while 
> everything is being wiped off underneath. However, the workqueue model tries 
> its best to schedule the work on the same CPU, though we can't use that 
> guarantee to ensure things will be fine.
>
> ---
> So I had to get a ref to the current vm till we had any pending work scheduled. 

I think that's the right thing to do.

> I think I put in comments in the code, but sadly most of my comments we stripped out before the merge.
>   

Pity.

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.


  parent reply	other threads:[~2008-12-29 13:19 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-12-25  9:09 [PATCH 0/15] Device assignment & MSI enhancement Sheng Yang
2008-12-25  9:09 ` [PATCH 01/15] KVM: Add MSI_ACTION flag for assigned irq Sheng Yang
2008-12-25  9:09 ` [PATCH 02/15] KVM: Use kvm_free_assigned_irq() for free irq Sheng Yang
2008-12-25  9:09 ` [PATCH 03/15] KVM: Add support to disable MSI for assigned device Sheng Yang
2008-12-25  9:09 ` [PATCH 04/15] KVM: Add a route layer to convert MSI message to GSI Sheng Yang
2008-12-25  9:09 ` [PATCH 05/15] KVM: Using gsi_msg mapping for MSI device assignment Sheng Yang
2008-12-25  9:09 ` [PATCH 06/15] KVM: Improve MSI dispatch function Sheng Yang
2008-12-25  9:09 ` [PATCH 07/15] KVM: Using ioapic_irqchip() macro for kvm_set_irq Sheng Yang
2008-12-25  9:09 ` [PATCH 08/15] KVM: Merge MSI handling to kvm_set_irq Sheng Yang
2008-12-25  9:09 ` [PATCH 09/15] KVM: Split IOAPIC structure Sheng Yang
2008-12-25  9:09 ` [PATCH 10/15] KVM: Unified the delivery of IOAPIC and MSI Sheng Yang
2008-12-25  9:09 ` [PATCH 11/15] KVM: Change API of kvm_ioapic_get_delivery_bitmask Sheng Yang
2008-12-25  9:09 ` [PATCH 12/15] KVM: Update intr delivery func to accept unsigned long* bitmap Sheng Yang
2008-12-25  9:09 ` [PATCH 13/15] KVM: bit ops for deliver_bitmap Sheng Yang
2008-12-25  9:09 ` [PATCH 14/15] KVM: Using kfifo for irq recording Sheng Yang
2008-12-26  2:29   ` [PATCH 14/15] KVM: Replace host_irq_disable with a new flag Sheng Yang
2008-12-25  9:09 ` [PATCH 15/15] KVM: Fix racy in kvm_free_assigned_irq Sheng Yang
2008-12-25 11:56   ` Sheng Yang
2008-12-26  2:30     ` Sheng Yang
2008-12-27 20:06       ` Marcelo Tosatti
2008-12-27 20:15         ` Marcelo Tosatti
2008-12-28 11:24         ` Sheng Yang
2008-12-28 12:57           ` Avi Kivity
2008-12-29  5:42           ` Amit Shah
2008-12-29 12:23             ` Sheng Yang
2008-12-29 13:37               ` Avi Kivity
2008-12-29 13:49                 ` Sheng Yang
2008-12-29 15:20               ` Marcelo Tosatti
2008-12-30  2:14                 ` Sheng Yang
2008-12-30 16:45                   ` Marcelo Tosatti
2008-12-31  5:43                     ` Sheng Yang
2009-01-02  0:10                       ` Marcelo Tosatti
2009-01-05  7:07                         ` Sheng Yang
2009-01-05 13:27                           ` Avi Kivity
2009-01-06  1:25                             ` Sheng Yang
2008-12-29 13:20             ` Avi Kivity [this message]
2008-12-25  9:13 ` [PATCH 0/15] Device assignment & MSI enhancement Sheng Yang

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