Re: Re: Re: [PATCH 09/11] drivers: infiniband: hw: Fix deadlock in irdma_cleanup_cm_core()

[duoming@zju.edu.cn]

Hello,

On Thu, 7 Apr 2022 11:23:55 -0300 Jason Gunthorpe wrote:

> > > > diff --git a/drivers/infiniband/hw/irdma/cm.c b/drivers/infiniband/hw/irdma/cm.c
> > > > index dedb3b7edd8..019dd8bfe08 100644
> > > > +++ b/drivers/infiniband/hw/irdma/cm.c
> > > > @@ -3252,8 +3252,11 @@ void irdma_cleanup_cm_core(struct irdma_cm_core *cm_core)
> > > >  		return;
> > > >  
> > > >  	spin_lock_irqsave(&cm_core->ht_lock, flags);
> > > > -	if (timer_pending(&cm_core->tcp_timer))
> > > > +	if (timer_pending(&cm_core->tcp_timer)) {
> > > > +		spin_unlock_irqrestore(&cm_core->ht_lock, flags);
> > > >  		del_timer_sync(&cm_core->tcp_timer);
> > > > +		spin_lock_irqsave(&cm_core->ht_lock, flags);
> > > > +	}
> > > >  	spin_unlock_irqrestore(&cm_core->ht_lock, flags);
> > > 
> > > This lock doesn't seem to be protecting anything.  Also do we need to
> > > check timer_pending()?  I think the del_timer_sync() function will just
> > > return directly if there isn't a pending lock?
> > 
> > Thanks a lot for your advice, I will remove the timer_pending() and the
> > redundant lock.
> 
> Does del_timer_sync work with a self-rescheduling timer like this has?

The del_timer_sync() will kill the timer although it is self-rescheduling.
We could use other functions to arouse timer again besides timer handler itself.

Best regards,
Duoming Zhou