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Re: [PATCH 4/5] linux: Optimize posix_spawn spurious sigaction calls

* Christian Brauner:

>> >>>>> Maybe a CLONE_RESET_SIGNALS where the cloned process sets its signal
>> >>>>> disposition to default SIG_IGN/SIG_DFL values may help us here.  However
>> >>>>> afaik clone now is out of space on 'flags' for newer ones (it already
>> >>>>> defines 24 flags plus it reserve 8 bits for signal to be sent at process
>> >>>>> exit) and it would take time to use this feature on glibc.
>> >>>>
>> >>>> Christian Brauner has been working on fixing this.
>> >>>
>> >>> Which strategy he is proposing? Even with proper kernel support, it would
>> >>> take time to enable glibc to use it.
>> >>
>> >> Lots of flag arguments, with the reset of the arguments located
>> >> indirectly via a pointer argument.
>> >>
>> >> For a pure optimization, I think it's not too bad to require kernel
>> >> backports of system calls.
> So I just accidently caught wind of this discussion. :)

Good. 8-)

> I'm open to extending clone3() to support something like the above.
> My new clone3() version has been released with Linux 5.3. It takes a
> struct clone_args. The structure is versioned by size and thus - in
> theory - extensible indefinitely.

Christian, would you be able to implement the CLONE_RESET_SIGNALS flag
for us?  It should reset any handler which is not SIG_IGN or SIG_DFL to
SIG_DFL.  We'd also need a way to probe that the flag is supported, so
that we can fall back to the current way of doing things otherwise.


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