Messages in this thread | | | From | Linus Torvalds <> | Date | Mon, 21 Jun 2021 08:38:14 -0700 | Subject | Re: Kernel stack read with PTRACE_EVENT_EXIT and io_uring threads |
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On Mon, Jun 21, 2021 at 6:55 AM Al Viro <viro@zeniv.linux.org.uk> wrote: > > On Tue, Jun 15, 2021 at 02:58:12PM -0700, Linus Torvalds wrote: > > > And I think our horrible "kernel threads return to user space when > > done" is absolutely horrifically nasty. Maybe of the clever sort, but > > mostly of the historical horror sort. > > How would you prefer to handle that, then? Separate magical path from > kernel_execve() to switch to userland? We used to have something of > that sort, and that had been a real horror...
Hmm. Maybe the alternatives would all be worse. The current thing is clever, and shares the return path with the normal case. It's just also a bit surprising, in that a kernel thread normally must not return - with the magical exception of "if it had done a kernel_execve() at some point, then returning is magically the way you actually start user mode".
So it all feels very special, and there's not even a comment about it.
I think we only have two users of that thing (the very first 'init', and user-mode-helpr), So I guess it doesn't really matter.
Linus
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