Re: kern/50430: syscall_disestablish() can remove active syscalls

[Masao Uebayashi <uebayasi%gmail.com@localhost>]

On Mon, Nov 16, 2015 at 6:45 AM, Christos Zoulas <christos%zoulas.com@localhost> wrote:
> On Nov 15,  8:25pm, mrg%eterna.com.au@localhost (matthew green) wrote:
> -- Subject: re: kern/50430: syscall_disestablish() can remove active syscalls
>
> |  until bug is fixed, can we disable the autounload?
>
> Sure, that sounds prudent. It is difficult to fix properly. One way to do
> this would be to mark all lwps that have used compat syscalls with a bit
> depending on the module they have used, and refuse to unload the module
> until the lwp is gone.
>
> - when load a module that has compat syscalls, assign to it a bit.
> - mark a flags field of all syscalls that were loaded with that module
>   with that bit.
> - or the lwp flags with the syscall flags on each syscall.
> - when it is time to unload check that no lwp has that bit in the flags set.
> - instead of keeping l_sysent, keep l_sysmodflags or something.

What happens if signal handler does longjmp(3) and interrupted syscall
never returns?