On Wed, Apr 29, 2020 at 3:38 PM Linus Torvalds
<torva...@linux-foundation.org> wrote:
>
> If you do it properly, with a helper function instead of repeating
> that fragile nasty thing, maybe it will look better to me.
Side note: if it has a special helper function for the "get lock,
repeat if it was invalid", you can do a better job than return
-EAGAIN.
In particular, you can do this
set_thread_flag(TIF_SIGPENDING);
return -RESTARTNOINTR;
which will actually restart the system call. So a ptrace() user (or
somebody doing a "write()" to /proc/<pid>/attr/xyz, wouldn't even see
the impossible EAGAIN error.
But that all requires that you have some locking helper routines like
int lock_exec_creds(struct task_struct *);
void unlock_exec_guard(struct task_struct *);
because there's no way we put that kind of super-fragile code in
several places. It would be very much one single routine with a *HUGE*
comment on it.
Linus
