Re: Linux 3.11-rc4

[Linus Torvalds]

On Mon, Aug 5, 2013 at 6:29 AM, Oleg Nesterov <oleg@xxxxxxxxxx> wrote:
>
> I never used wine, but I am puzzled anyway. This patch really looks
> like a simple and minor bugfix.

The patch is indeed trivial, but.. What's the locking here?

Afaik, ptrace_detach() by the parent can race with do_exit() by the
child, and they now _both_ do flush_ptrace_hw_breakpoint(). Or am I
wrong? We have that whole "get tasklist_lock for writing and then
check child->ptrace" logic there exactly due to that race, no?

That said, Felipe, can you double-check that it's not timing-related
in some subtle way, and test multiple times with just that commit
reverted (and not reverted) to make sure that it's 100% that one
single line by that particular commit? Because it does seem very
benign..

               Linus
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