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

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Date:	Thu, 14 Apr 2016 16:51:38 +0200 (CEST)
From:	Jiri Kosina <jikos@...nel.org>
To:	Jamal Hadi Salim <jhs@...atatu.com>
cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Deleting child qdisc doesn't reset parent to default qdisc?

On Thu, 14 Apr 2016, Jiri Kosina wrote:

> In a nutshell, is this expected behavior or bug?

Just to clarify what seems to suggest to me that this is rather a bug that 
needs to be fixed (but apparently one that has been there for quite a long 
time) can be demonstrated by this:

> 
> =====
> jikos:~ # tc qdisc show
> qdisc tbf 10: dev eth0 root refcnt 2 rate 800Mbit burst 131000b lat 1.0ms 

The above configuration works.

> jikos:~ # ping -c 1 nix.cz | head -2
> PING nix.cz (195.47.235.3) 56(84) bytes of data.
> 64 bytes from info.nix.cz (195.47.235.3): icmp_seq=1 ttl=89 time=1.59 ms
> 
> jikos:~ # tc qdisc add dev eth0 parent 10:1 sfq
> jikos:~ # tc qdisc show
> qdisc tbf 10: dev eth0 root refcnt 2 rate 800Mbit burst 131000b lat 1.0ms 
> qdisc sfq 8008: dev eth0 parent 10:1 limit 127p quantum 1514b depth 127 divisor 1024 
> 
> jikos:~ # ping -c 1 nix.cz | head -2
> PING nix.cz (195.47.235.3) 56(84) bytes of data.
> 64 bytes from info.nix.cz (195.47.235.3): icmp_seq=1 ttl=89 time=1.67 ms
> 
> jikos:~ # tc qdisc del dev eth0 parent 10:1 sfq
> jikos:~ # tc qdisc show
> qdisc tbf 10: dev eth0 root refcnt 2 rate 800Mbit burst 131000b lat 1.0ms 

The above configuration doesn't although it's identical to the working one 
at the beginning.

> jikos:~ # ping -c 1 nix.cz | head -2
> PING nix.cz (195.47.235.3) 56(84) bytes of data.
> 	[ ... nothing happens ... ]
> ^C

-- 
Jiri Kosina
SUSE Labs