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Re: [Qemu-devel] [RFC v2 10/11] tcg: drop global lock during TCG code ex

From: Paolo Bonzini
Subject: Re: [Qemu-devel] [RFC v2 10/11] tcg: drop global lock during TCG code execution
Date: Wed, 25 May 2016 14:46:42 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.0

On 25/05/2016 13:07, Alex Bennée wrote:
>>>> + * If called from generated code, iothread mutex must not be held.
>>> What does that mean? If iothread mutex is not required by the function
>>> then why mention it here at all?
>> If this function can take the iothread mutex itself, this would cause a
>> deadlock.  I'm not sure if it could though.
>> Another possibility is that this function can longjmp out into cpu_exec,
>> and then the iothread mutex would not be released.  I think this is more
>> likely.
> Any longjmp should:
>             tb_lock_reset();
>             if (qemu_mutex_iothread_locked()) {
>                 qemu_mutex_unlock_iothread();
>             }
> To reset the locks.

Ok, so I think these comments are stale, dating to before you added the
unlock_iothread in the sigsetjmp else.



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