All of lore.kernel.org
 help / color / mirror / Atom feed
From: Luis Chamberlain <mcgrof@kernel.org>
To: Bart Van Assche <bvanassche@acm.org>
Cc: Jan Kara <jack@suse.cz>, Jens Axboe <axboe@kernel.dk>,
	linux-block@vger.kernel.org
Subject: Re: [PATCH] blktrace: Avoid sparse warnings when assigning q->blk_trace
Date: Thu, 28 May 2020 14:55:39 +0000	[thread overview]
Message-ID: <20200528145539.GS11244@42.do-not-panic.com> (raw)
In-Reply-To: <298af02a-3b58-932a-8769-72dcc52750ad@acm.org>

On Thu, May 28, 2020 at 07:44:38AM -0700, Bart Van Assche wrote:
> > @@ -1669,10 +1672,7 @@ static int blk_trace_setup_queue(struct request_queue *q,
> >  
> >  	blk_trace_setup_lba(bt, bdev);
> >  
> > -	ret = -EBUSY;
> > -	if (cmpxchg(&q->blk_trace, NULL, bt))
> > -		goto free_bt;
> > -
> > +	rcu_assign_pointer(q->blk_trace, bt);
> >  	get_probe_ref();
> >  	return 0;
> 
> Shouldn't q->blk_trace only be assigned if
> q->blk_trace == NULL?

Yes but the old call checked for that and left it as NULL if
it was not NULL.

I have a patch in my series which checks for q->blkt_trace *early*
prior to continuing to avoid concurrent calls proactively, otherwise
this will fail only at the very end.

  Luis

  reply	other threads:[~2020-05-28 14:55 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-28  9:29 [PATCH] blktrace: Avoid sparse warnings when assigning q->blk_trace Jan Kara
2020-05-28 14:44 ` Bart Van Assche
2020-05-28 14:55   ` Luis Chamberlain [this message]
2020-05-28 18:31   ` Jan Kara
2020-05-28 18:43     ` Luis Chamberlain
2020-05-28 18:55       ` Jan Kara
2020-05-29  8:00         ` Luis Chamberlain
2020-05-29  9:04           ` Jan Kara
2020-05-29 11:43             ` Luis Chamberlain
2020-05-29 12:11               ` Jan Kara
2020-05-29 12:22                 ` Luis Chamberlain
2020-06-02  7:12 Jan Kara
2020-06-02 14:17 ` Luis Chamberlain
2020-06-02 15:10   ` Luis Chamberlain
2020-06-03  8:35     ` Jan Kara

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=20200528145539.GS11244@42.do-not-panic.com \
    --to=mcgrof@kernel.org \
    --cc=axboe@kernel.dk \
    --cc=bvanassche@acm.org \
    --cc=jack@suse.cz \
    --cc=linux-block@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
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.