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Re: [Qemu-devel] [PULL 15/36] memory: fix race between TCG and accesses
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From: |
Paolo Bonzini |
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Subject: |
Re: [Qemu-devel] [PULL 15/36] memory: fix race between TCG and accesses to dirty bitmap |
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Date: |
Thu, 12 Sep 2019 14:45:52 +0200 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 |
On 26/08/19 14:19, dovgaluk wrote:
> This patch breaks the execution recording.
> While vCPU tries to lock replay mutex in main while loop,
> vga causes dirty memory sync and do_run_on_cpu call.
> This call waits for vCPU to process the work queue.
IIUC there is a deadlock because VGA (from the I/O thread) is holding
the replay mutex. Next time, please include a quick description of who
waits for whom. :)
I think it should be enough to wrap the do_run_on_cpu on replay_mode ==
REPLAY_MODE_NONE, since the I/O and vCPU thread are anyway running in
lockstep when rr is active. (This reasoning should also be in a comment).
Paolo