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Message-ID: <20220407142355.GV64706@ziepe.ca>
Date: Thu, 7 Apr 2022 11:23:55 -0300
From: Jason Gunthorpe <jgg@...pe.ca>
To: duoming@....edu.cn
Cc: Dan Carpenter <dan.carpenter@...cle.com>,
linux-kernel@...r.kernel.org, chris@...kel.net, jcmvbkbc@...il.com,
mustafa.ismail@...el.com, shiraz.saleem@...el.com,
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kuba@...nel.org, pabeni@...hat.com, jes@...ined-monkey.org,
gregkh@...uxfoundation.org, jirislaby@...nel.org,
alexander.deucher@....com, linux-xtensa@...ux-xtensa.org,
linux-rdma@...r.kernel.org, linux-can@...r.kernel.org,
netdev@...r.kernel.org, linux-hippi@...site.dk,
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Subject: Re: Re: [PATCH 09/11] drivers: infiniband: hw: Fix deadlock in
irdma_cleanup_cm_core()
On Thu, Apr 07, 2022 at 08:54:13PM +0800, duoming@....edu.cn 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?
Jason
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