Re: [PATCH] system/runstate: Fix regression, clarify BQL status of exit notifiers

[David Woodhouse <dwmw2@infradead.org>]

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On Sun, 2025-01-12 at 22:26 +0100, Phil Dennis-Jordan wrote:
> By changing the way the main QEMU event loop is invoked, I inadvertently
> changed the BQL status of exit notifiers: some of them implicitly
> assumed they would be called with the BQL held; the BQL is however
> not held during the exit(status) call in qemu_default_main().
> 
> Instead of attempting to ensuring we always call exit() from the BQL -
> including any transitive calls - this change adds a BQL lock guard to
> qemu_run_exit_notifiers, ensuring the BQL will always be held in the
> exit notifiers.
> 
> Additionally, the BQL promise is now documented at the
> qemu_{add,remove}_exit_notifier() declarations.
> 
> Fixes: f5ab12caba4f ("ui & main loop: Redesign of system-specific main
> thread event handling")
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2771
> Reported-by: David Woodhouse <dwmw2@infradead.org>
> Signed-off-by: Phil Dennis-Jordan <phil@philjordan.eu>

Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
Tested-by: David Woodhouse <dwmw@amazon.co.uk>

(Sorry, I thought I'd done that already).

Is someone else going to pick this up, or should I round it up with the
Xen fixes for which I'm likely to send a pull request tomorrow? 

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