Re: Deleting child qdisc doesn't reset parent to default qdisc?

From	Eric Dumazet <eric.dumazet@gmail.com>
Newsgroups	linux.kernel
Subject	Re: Deleting child qdisc doesn't reset parent to default qdisc?
Date	2016-04-15 17:00 +0200
Message-ID	<rodnY-4BO-5@gated-at.bofh.it> (permalink)
References	(1 earlier) <rnR48-3Fm-83@gated-at.bofh.it> <rnRdM-3Ro-31@gated-at.bofh.it> <rnS0b-4DT-27@gated-at.bofh.it> <rnTyX-5JF-39@gated-at.bofh.it> <robma-36m-15@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Fri, 2016-04-15 at 08:42 -0400, Jamal Hadi Salim wrote:
> On 16-04-14 01:49 PM, Eric Dumazet wrote:
> 
> > And what would be the chosen behavior ?
> >
> 
> TBF is probably a bad example because it started life as
> a classless qdisc. There was only one built-in fifo queue
> that was shaped. Then someone made it classful and changed
> this behavior. To me it sounds reasonable to have the
> default behavior restored. At minimal consistency.

Then you need to save the initial qdisc (bfifo for TBF) in a special
place, to make sure the delete operation is guaranteed to succeed.

Or fail the delete if the bfifo can not be allocated.

I can tell that determinism if far more interesting than usability for
some users occasionally playing with tc.

Surely the silent fallback to noop_qdisc is wrong.

Anyway, we probably need to improve our ability to understand qdisc
hierarchies. Having some hidden qdiscs is the real problem here.

We need to add some hash table so that qdisc_match_from_root() does not
have to scan hundred of qdiscs.

Thread

Deleting child qdisc doesn't reset parent to default qdisc? Jiri Kosina <jikos@kernel.org> - 2016-04-14 16:50 +0200
  Re: Deleting child qdisc doesn't reset parent to default qdisc? Jiri Kosina <jikos@kernel.org> - 2016-04-14 17:00 +0200
  Re: Deleting child qdisc doesn't reset parent to default qdisc? Eric Dumazet <eric.dumazet@gmail.com> - 2016-04-14 17:10 +0200
    Re: Deleting child qdisc doesn't reset parent to default qdisc? Phil Sutter <phil@nwl.cc> - 2016-04-14 17:20 +0200
      Re: Deleting child qdisc doesn't reset parent to default qdisc? Jiri Kosina <jikos@kernel.org> - 2016-04-14 17:40 +0200
        Re: Deleting child qdisc doesn't reset parent to default qdisc? Eric Dumazet <eric.dumazet@gmail.com> - 2016-04-14 17:50 +0200
          Re: Deleting child qdisc doesn't reset parent to default qdisc? Phil Sutter <phil@nwl.cc> - 2016-04-14 18:30 +0200
            Re: Deleting child qdisc doesn't reset parent to default qdisc? Eric Dumazet <eric.dumazet@gmail.com> - 2016-04-14 18:50 +0200
      Re: Deleting child qdisc doesn't reset parent to default qdisc? Jiri Kosina <jikos@kernel.org> - 2016-04-14 18:10 +0200
        Re: Deleting child qdisc doesn't reset parent to default qdisc? Eric Dumazet <eric.dumazet@gmail.com> - 2016-04-14 19:50 +0200
          Re: Deleting child qdisc doesn't reset parent to default qdisc? Jamal Hadi Salim <jhs@mojatatu.com> - 2016-04-15 14:50 +0200
            Re: Deleting child qdisc doesn't reset parent to default qdisc? Eric Dumazet <eric.dumazet@gmail.com> - 2016-04-15 17:00 +0200
              Re: Deleting child qdisc doesn't reset parent to default qdisc? David Miller <davem@davemloft.net> - 2016-04-15 19:20 +0200

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