[Bridge] [PATCH] net, bridge: print log message after state changed

Fritz, Wolfgang Wolfgang.Fritz at keymile.com
Mon Nov 14 09:09:45 UTC 2011


Am Montag, den 14.11.2011, 02:07 -0500 schrieb David Miller:
> From: "Fritz, Wolfgang" <Wolfgang.Fritz at keymile.com>
> Date: Mon, 14 Nov 2011 08:03:31 +0100
> 
> > 
> > Am Montag, den 14.11.2011, 00:37 -0500 schrieb David Miller:
> >> From: Holger Brunck <holger.brunck at keymile.com>
> >> Date: Thu, 10 Nov 2011 17:18:54 +0100
> >> 
> >> > From: Wolfgang Fritz <wolfgang.fritz at keymile.com>
> >> > 
> >> > Function br_log_state writes log message "... entering XXXX state" so it
> >> > should be called after the state has changed and not before.
> >> > 
> >> > Signed-off-by: Wolfgang Fritz <wolfgang.fritz at keymile.com>
> >> > Signed-off-by: Holger Brunck <holger.brunck at keymile.com>
> >> 
> >> "entering" can roughly mean "about to enter"
> >> 
> > 
> > Exactly.
> > 
> >> The message is therefore appropriately timed as far as I'm concerned.
> >> 
> > 
> > It's not.
> > 
> > Please test: create a bridge with STP disabled, add an interface to the
> > bridge and set that interface down. You get the message "... entering
> > forwarding state". That's wrong because it's "about to enter" disabled
> > state some lines later.
> > 
> > All other (4) calls to br_log_state are located after the state change,
> > see for example br_stp_enable_port() just some lines above the patch.
> 
> I would never expect an "entering" message to print out after the event
> happens, and in fact I'd _always_ want to see it beforehand so that if
> the state change caused a crash or similar it'd be that much easier
> to pinpoint the proper location.
> 

OK. I see what you mean.

Proposal 1 (simple): 
- Modify log message to "Entered xxx state"
- Apply patch
- Do not touch other br_log_message calls.

Proposal 2 (more complicated):
Add parameter "newstate" to br_log_message and put br_log_message before
the state change. Print log message only if new state != current state.

Advantage: Reduces log spam when STP is disabled. After the last
modifications to the bridge code which force "forwarding" state if STP
is disabled, you get lots of bogus messages "entering forwarding state":

Event                    old message      new message
link up                  learning         forwarding
forwarding delay expired forwarding       forwarding
interface down           disabled         forwarding
link down                disabled         forwarding  

If you accept one of the proposals, I'll prepare a patch. Otherwise, we
keep my original patch in our local tree.

> I'm still not applying this.  If the other log messages behave
> differently, they are broken, so go fix those instead.

Regards,
Wolfgang

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