Re: [PATCH v8 13/21] main: keep rcu_atfork callback enabled for qtest

[Stefan Hajnoczi]

On Wed, Jan 29, 2020 at 05:34:22AM +0000, Bulekov, Alexander wrote:
> The qtest-based fuzzer makes use of forking to reset-state between
> tests. Keep the callback enabled, so the call_rcu thread gets created
> within the child process.
> 
> Signed-off-by: Alexander Bulekov <address@hidden>
> ---
>  vl.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/vl.c b/vl.c
> index bb77935f04..cf8e2d3ebb 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -3794,7 +3794,14 @@ void qemu_init(int argc, char **argv, char **envp)
>      set_memory_options(&ram_slots, &maxram_size, machine_class);
>  
>      os_daemonize();
> -    rcu_disable_atfork();
> +
> +    /*
> +     * If QTest is enabled, keep the rcu_atfork enabled, since system 
> processes
> +     * may be forked testing purposes (e.g. fork-server based fuzzing)
> +     */
> +    if (!qtest_enabled()) {
> +        rcu_disable_atfork();
> +    }

I haven't reviewed the details of whether resources are leaked across
fork but in general it makes sense that we want an RCU thread in the
fork child:

Acked-by: Stefan Hajnoczi <address@hidden>

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