Re: spinlock contention of files->file_lock

[Linus Torvalds]

On Mon, Sep 30, 2013 at 6:53 PM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
>
> The problem is dup2()

Shouldn't a cmpxchg() in just the dup2 code solve that?

If the old value was NULL, you'd have to repeat and go back and see if
the open_fds[] bit had been cleared in the meantime (ie it's NULL not
because somebody else is busy installing it, but because somebody just
uninstalled it).

But yeah, I do agree that that sounds nasty and a complication I
hadn't even thought about. dup2() does violate our normal "let's
pre-allocate the fd slot" rule. Ugh.

              Linus
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/