linux-kernel - Re: [PATCH] uevent: send events in correct order according to seqnum

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Message-ID: <CAPXgP10qwPn2-QeyPpDy3GiEqvU6jB-wVuUOUXwcGBvOWOUA1Q@mail.gmail.com>
Date:	Tue, 6 Mar 2012 22:03:05 +0100
From:	Kay Sievers <kay.sievers@...y.org>
To:	Andrew Vagin <avagin@...nvz.org>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-hotplug@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] uevent: send events in correct order according to seqnum

On Tue, Mar 6, 2012 at 21:06, Andrew Vagin <avagin@...nvz.org> wrote:
>
> The queue handling in the udev daemon assumes that the events are
> ordered.
>
> Before this patch uevent_seqnum is incremented under sequence_lock,
> than an event is send uner uevent_sock_mutex. I want to say that code
> contained a window between incrementing seqnum and sending an event.
>
> This patch locks uevent_sock_mutex before incrementing uevent_seqnum.

I think we can remove the spin_lock(&sequence_lock); entirely now, right?

Also the section with:
  seq = ++uevent_seqnum;
can just be:
  add_uevent_var(env, "SEQNUM=%llu", (unsigned long long) ++uevent_seqnum);
right?

And the:
  mutex_lock(&uevent_sock_mutex);
can just move outside of the _NET ifdef and we always use the mutex
instead of the spinlock?

That could look much simpler than the current code, I think.

Thanks,
Kay
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