RCU Archive on lore.kernel.org
 help / color / Atom feed
From: Jason Gunthorpe <jgg@ziepe.ca>
To: Dennis Dalessandro <dennis.dalessandro@intel.com>
Cc: madhuparnabhowmik04@gmail.com, mike.marciniszyn@intel.com,
	paulmck@kernel.org, joel@joelfernandes.org, frextrite@gmail.com,
	linux-kernel-mentees@lists.linuxfoundation.org,
	rcu@vger.kernel.org, linux-rdma@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/3] infiniband: hw: hfi1: verbs.c: Use built-in RCU list checking
Date: Tue, 14 Jan 2020 15:41:48 -0400
Message-ID: <20200114194148.GD22037@ziepe.ca> (raw)
In-Reply-To: <25133367-6544-d0af-ae30-5178909748b1@intel.com>

On Tue, Jan 14, 2020 at 01:24:00PM -0500, Dennis Dalessandro wrote:
> On 1/14/2020 12:00 PM, Dennis Dalessandro wrote:
> > On 1/14/2020 11:57 AM, Jason Gunthorpe wrote:
> > > On Tue, Jan 14, 2020 at 09:53:45PM +0530,
> > > madhuparnabhowmik04@gmail.com wrote:
> > > > From: Madhuparna Bhowmik <madhuparnabhowmik04@gmail.com>
> > > > 
> > > > list_for_each_entry_rcu has built-in RCU and lock checking.
> > > > Pass cond argument to list_for_each_entry_rcu.
> > > > 
> > > > Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik04@gmail.com>
> > > >   drivers/infiniband/hw/hfi1/verbs.c | 2 +-
> > > >   1 file changed, 1 insertion(+), 1 deletion(-)
> > > > 
> > > > diff --git a/drivers/infiniband/hw/hfi1/verbs.c
> > > > b/drivers/infiniband/hw/hfi1/verbs.c
> > > > index 089e201d7550..22f2d4fd2577 100644
> > > > +++ b/drivers/infiniband/hw/hfi1/verbs.c
> > > > @@ -515,7 +515,7 @@ static inline void hfi1_handle_packet(struct
> > > > hfi1_packet *packet,
> > > >                          opa_get_lid(packet->dlid, 9B));
> > > >           if (!mcast)
> > > >               goto drop;
> > > > -        list_for_each_entry_rcu(p, &mcast->qp_list, list) {
> > > > +        list_for_each_entry_rcu(p, &mcast->qp_list, list,
> > > > lockdep_is_held(&(ibp->rvp.lock))) {
> > > 
> > > Okay, this looks reasonable
> > > 
> > > Mike, Dennis, is this the right lock to test?
> > > 
> > 
> > I'm looking at that right now actually, I don't think this is correct.
> > Wanted to talk to Mike before I send a response though.
> > 
> > -Denny
> 
> That's definitely going to throw a ton of lock dep messages. It's not really
> the right lock either. Instead what we probably need to do is what we do in
> the non-multicast part of the code and take the rcu_read_lock().

Uh.. why is this using the _rcu varient without holding the rcu lock?
That is quite wrong already.

Jason

  parent reply index

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-14 16:23 madhuparnabhowmik04
2020-01-14 16:57 ` Jason Gunthorpe
2020-01-14 17:00   ` Dennis Dalessandro
2020-01-14 18:24     ` Dennis Dalessandro
2020-01-14 19:17       ` Joel Fernandes
2020-01-14 19:41       ` Jason Gunthorpe [this message]
2020-01-14 19:46         ` Dennis Dalessandro
  -- strict thread matches above, loose matches on Subject: below --
2020-01-07 19:29 madhuparnabhowmik04
2020-01-07 20:33 ` Jason Gunthorpe
2020-01-09 18:10   ` Jason Gunthorpe
2020-01-10 15:54   ` Joel Fernandes
2020-01-07 17:35 madhuparnabhowmik04
2020-01-07 18:26 ` Jason Gunthorpe

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200114194148.GD22037@ziepe.ca \
    --to=jgg@ziepe.ca \
    --cc=dennis.dalessandro@intel.com \
    --cc=frextrite@gmail.com \
    --cc=joel@joelfernandes.org \
    --cc=linux-kernel-mentees@lists.linuxfoundation.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-rdma@vger.kernel.org \
    --cc=madhuparnabhowmik04@gmail.com \
    --cc=mike.marciniszyn@intel.com \
    --cc=paulmck@kernel.org \
    --cc=rcu@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

RCU Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/rcu/0 rcu/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 rcu rcu/ https://lore.kernel.org/rcu \
		rcu@vger.kernel.org
	public-inbox-index rcu

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.rcu


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git