On Tuesday, January 04, 2011 10:09:15 Eugene Grosbein wrote:
quoted text
> On 04.01.2011 15:06, Bernhard Schmidt wrote:
> >> Perhaps, wrapping wpa_supplicant invocation into "lockf -t0" would help
> >> to eliminate race?
> > 
> > Possibly, but I don't think this is the way to go.
> > 
> > Currently wpa_supplicant has this code:
> >         /*
> >         
> >          * Mark the interface as down to ensure wpa_supplicant has
> >          exclusive * access to the net80211 state machine, do this
> >          before opening the * route socket to avoid a false event that
> >          the interface disappeared. */
> >         
> >         if (getifflags(drv, &flags) == 0)
> >         
> >                 (void) setifflags(drv, flags &~ IFF_UP);
> > 
> > This code works such that it will send an event to already running
> > wpa_supplicant instances which will then terminate. This does indeed work
> > if there's enough delay between invocations, though, if there is just a
> > small delay (~100ms or something), that event doesn't get passed
> > probably. I think we should start looking into possible solution at that
> > point, trying to figure out why the the event doesn't get passed
> > (probably because the interface is not yet up at that point) will get us
> > closer to proper solution.
> 
> Proper fine-grained locking was always good solution for race problem :-)
> How about using flock(2) in wpa_supplicant source code?

I don't see any flock'able resource shared between instances, do you?

-- 
Bernhard
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