netdev - Re: [PATCH] ieee80211softmac: Fix errors related to the work

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Date:	Sun, 10 Dec 2006 19:35:36 +0100
From:	Ulrich Kunitz <kune@...ne-taler.de>
To:	Michael Buesch <mb@...sch.de>
Cc:	netdev@...r.kernel.org, Andrew Morton <akpm@...l.org>,
	"John W. Linville" <linville@...driver.com>,
	Johannes Berg <johannes@...solutions.net>, dsd@...too.org
Subject: Re: [PATCH] ieee80211softmac: Fix errors related to the work_struct changes

On 06-12-10 18:49 Michael Buesch wrote:

> On Sunday 10 December 2006 18:39, Ulrich Kunitz wrote:
> > The signature of work functions changed recently from a context
> > pointer to the work structure pointer. This caused a problem in
> > the ieee80211softmac code, because the ieee80211softmac_assox_work
> > function has  been called directly with a parameter explicitly
> > casted to (void*). This compiled correctly but resulted in a
> > softlock, because mutex_lock was called with the wrong memory
> > address. The patch fixes the problem. Another issue was a wrong
> > call of the schedule_work function. Softmac works again and this
> > fixes the problem I mentioned earlier in the zd1211rw rx tasklet
> > patch. The patch is against Linus' tree (commit af1713e0).
> > 
> > Signed-off-by: Ulrich Kunitz <kune@...ne-taler.de>
> > ---
> >  net/ieee80211/softmac/ieee80211softmac_assoc.c |    6 +++---
> >  1 files changed, 3 insertions(+), 3 deletions(-)
> > 
> > diff --git a/net/ieee80211/softmac/ieee80211softmac_assoc.c b/net/ieee80211/softmac/ieee80211softmac_assoc.c
> > index eec1a1d..a824852 100644
> > --- a/net/ieee80211/softmac/ieee80211softmac_assoc.c
> > +++ b/net/ieee80211/softmac/ieee80211softmac_assoc.c
> > @@ -167,7 +167,7 @@ static void
> >  ieee80211softmac_assoc_notify_scan(struct net_device *dev, int event_type, void *context)
> >  {
> >  	struct ieee80211softmac_device *mac = ieee80211_priv(dev);
> > -	ieee80211softmac_assoc_work((void*)mac);
> > +	ieee80211softmac_assoc_work(&mac->associnfo.work.work);
> >  }
> >  
> >  static void
> > @@ -177,7 +177,7 @@ ieee80211softmac_assoc_notify_auth(struc
> >  
> >  	switch (event_type) {
> >  	case IEEE80211SOFTMAC_EVENT_AUTHENTICATED:
> > -		ieee80211softmac_assoc_work((void*)mac);
> > +		ieee80211softmac_assoc_work(&mac->associnfo.work.work);
> >  		break;
> >  	case IEEE80211SOFTMAC_EVENT_AUTH_FAILED:
> >  	case IEEE80211SOFTMAC_EVENT_AUTH_TIMEOUT:
> > @@ -438,7 +438,7 @@ ieee80211softmac_try_reassoc(struct ieee
> >  
> >  	spin_lock_irqsave(&mac->lock, flags);
> >  	mac->associnfo.associating = 1;
> > -	schedule_work(&mac->associnfo.work);
> > +	schedule_delayed_work(&mac->associnfo.work, 0);
> 
> Why do you use a zero delay here? What does that fix?
> 

The problem is that you there are now different work structures:
struct work_struct and struct delayed_work. The quick fix seems to
have been to change all old work_structs as associnfo's work to
delayed_work. The way the structures are designed calling
schedule_work or schedule_delayed_work doesn't matter, but you
will get a gcc warning, because the pointer types are not
identical. This change works around the warning in the same way as
the other schedule_work calls for associnfo's work.

I'm not sure, whether the breaking of the workqueue API is really
worth it. What I see is that the change introduced choices and
choices make things more complex.

-- 
Uli Kunitz
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