LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Peter Zijlstra <peterz@infradead.org>
To: Andrea Parri <andrea.parri@amarulasolutions.com>
Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org,
	Dennis Dalessandro <dennis.dalessandro@intel.com>,
	Mike Marciniszyn <mike.marciniszyn@intel.com>,
	Doug Ledford <dledford@redhat.com>,
	Jason Gunthorpe <jgg@ziepe.ca>,
	linux-rdma@vger.kernel.org
Subject: Re: [PATCH 5/5] IB/hfi1: Fix improper uses of smp_mb__before_atomic()
Date: Tue, 30 Apr 2019 10:28:14 +0200	[thread overview]
Message-ID: <20190430082814.GC2677@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <1556568902-12464-6-git-send-email-andrea.parri@amarulasolutions.com>

On Mon, Apr 29, 2019 at 10:15:01PM +0200, Andrea Parri wrote:
> This barrier only applies to the read-modify-write operations; in
> particular, it does not apply to the atomic_read() primitive.
> 
> Replace the barrier with an smp_mb().
> 
> Fixes: 856cc4c237add ("IB/hfi1: Add the capability for reserved operations")
> Cc: stable@vger.kernel.org
> Reported-by: "Paul E. McKenney" <paulmck@linux.ibm.com>
> Reported-by: Peter Zijlstra <peterz@infradead.org>
> Signed-off-by: Andrea Parri <andrea.parri@amarulasolutions.com>
> Cc: Dennis Dalessandro <dennis.dalessandro@intel.com>
> Cc: Mike Marciniszyn <mike.marciniszyn@intel.com>
> Cc: Doug Ledford <dledford@redhat.com>
> Cc: Jason Gunthorpe <jgg@ziepe.ca>
> Cc: linux-rdma@vger.kernel.org
> ---
>  drivers/infiniband/sw/rdmavt/qp.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/infiniband/sw/rdmavt/qp.c b/drivers/infiniband/sw/rdmavt/qp.c
> index a34b9a2a32b60..b64fd151d31fb 100644
> --- a/drivers/infiniband/sw/rdmavt/qp.c
> +++ b/drivers/infiniband/sw/rdmavt/qp.c
> @@ -1863,11 +1863,11 @@ static inline int rvt_qp_is_avail(
>  	u32 reserved_used;
>  
>  	/* see rvt_qp_wqe_unreserve() */

I see a completely bogus comment in rvf_op_wqe_unreserve(), referring to
bogus comments makes this barrier bogus too.

> -	smp_mb__before_atomic();
> +	smp_mb();
>  	reserved_used = atomic_read(&qp->s_reserved_used);
>  	if (unlikely(reserved_op)) {
>  		/* see rvt_qp_wqe_unreserve() */
> -		smp_mb__before_atomic();

This was before, but there is nothing _after_ this. Which means this
barrier was complete garbage anyway.

> +		smp_mb();
>  		if (reserved_used >= rdi->dparms.reserved_operations)
>  			return -ENOMEM;
>  		return 0;
> @@ -1882,7 +1882,7 @@ static inline int rvt_qp_is_avail(
>  		avail = slast - qp->s_head;
>  
>  	/* see rvt_qp_wqe_unreserve() */
> -	smp_mb__before_atomic();
> +	smp_mb();

Same as the first.

>  	reserved_used = atomic_read(&qp->s_reserved_used);
>  	avail =  avail - 1 -
>  		(rdi->dparms.reserved_operations - reserved_used);

  parent reply	other threads:[~2019-04-30  8:28 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-29 20:14 [PATCH 0/5] Fix improper uses of smp_mb__{before,after}_atomic() Andrea Parri
2019-04-29 20:14 ` [PATCH 1/5] drm/msm: " Andrea Parri
2019-05-09 20:19   ` Andrea Parri
2019-04-29 20:14 ` [PATCH 2/5] bio: fix improper use of smp_mb__before_atomic() Andrea Parri
2019-04-30  8:21   ` Peter Zijlstra
2019-05-09 20:23   ` Andrea Parri
2019-05-10  3:40   ` Ming Lei
2019-04-29 20:14 ` [PATCH 3/5] sbitmap: " Andrea Parri
2019-05-09 20:26   ` Andrea Parri
2019-05-10  3:41   ` Ming Lei
2019-05-10  6:27     ` Andrea Parri
2019-04-29 20:15 ` [PATCH 4/5] ceph: " Andrea Parri
2019-04-30  8:23   ` Peter Zijlstra
2019-04-30  9:08     ` Yan, Zheng
2019-05-09 20:55       ` Andrea Parri
2019-05-13 13:04         ` Yan, Zheng
2019-05-13 22:47           ` Andrea Parri
2019-04-29 20:15 ` [PATCH 5/5] IB/hfi1: Fix improper uses " Andrea Parri
2019-04-29 21:24   ` Ruhl, Michael J
2019-04-29 23:16     ` Andrea Parri
2019-05-09 21:12       ` Andrea Parri
2019-05-14 12:32         ` Dennis Dalessandro
2019-05-14 14:48           ` Andrea Parri
2019-04-30  8:28   ` Peter Zijlstra [this message]
2019-04-30  8:34 ` [PATCH 0/5] Fix improper uses of smp_mb__{before,after}_atomic() Peter Zijlstra
2019-04-30 16:44   ` Andrea Parri

Reply instructions:

You may reply publicly 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=20190430082814.GC2677@hirez.programming.kicks-ass.net \
    --to=peterz@infradead.org \
    --cc=andrea.parri@amarulasolutions.com \
    --cc=dennis.dalessandro@intel.com \
    --cc=dledford@redhat.com \
    --cc=jgg@ziepe.ca \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-rdma@vger.kernel.org \
    --cc=mike.marciniszyn@intel.com \
    --cc=stable@vger.kernel.org \
    --subject='Re: [PATCH 5/5] IB/hfi1: Fix improper uses of smp_mb__before_atomic()' \
    /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

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).