From mboxrd@z Thu Jan  1 00:00:00 1970
From: Will Deacon <will.deacon@arm.com>
Subject: Re: [PATCH 4/5] Fix a race during exit processing
Date: Mon, 11 Apr 2016 16:37:29 +0100
Message-ID: <20160411153728.GB19749@arm.com>
References: <1459423707-8956-1-git-send-email-bsingharora@gmail.com>
 <1459423707-8956-5-git-send-email-bsingharora@gmail.com>
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Cc: kvm@vger.kernel.org, mpe@ellerman.id.au, mikey@neuling.org
To: Balbir Singh <bsingharora@gmail.com>
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On Thu, Mar 31, 2016 at 10:28:26PM +1100, Balbir Singh wrote:
> Fix a race, described below
> 
> 	lkvm stop ...	handle_stop
> 			kvm_cpu__reboot
> 			kvm_cmd_run_exit
> 			vcpus exit
> 			...
> 			dev_exit
> 			...
> 			ioport__unregister
> 			..serial...
> 			kvm__pause --> br_write_lock
> 			pthread_kill
> 
> But the thread is already dead above.
> 
> We mark the cpus as dying so that kvm_pause does nothing.
> This should not break any semantics

I'm not convinced that this solves the whole problem. The fact of the
matter is that we're tearing down the VM whilst there may still be active
vcpus, so I'd much rather delay the teardown until we know that the vcpus
are all dead.

Patch incoming.

Will