Re: Thread safety of coroutine-sigaltstack

[Max Reitz]

On 20.01.21 18:25, Laszlo Ersek wrote:

[...]

> A simple grep for SIGUSR2 seems to indicate that SIGUSR2 is not used by
> system emulation for anything else, in practice. Is it possible to
> dedicate SIGUSR2 explicitly to coroutine-sigaltstack, and set up the
> action beforehand, from some init function that executes on a "central"
> thread, before qemu_coroutine_new() is ever called?

I wrote a patch to that effect, but just before sending I wondered 
whether SIGUSR2 cannot be registered by the “guest” in user-mode 
emulation, and whether that would then break coroutines from there on.

(I have no experience dealing with user-mode emulation, but it does look 
like the guest can just register handlers for any signal but SIGSEGV and 
SIGBUS.)

Max