From: Brian Foster <bfoster@redhat.com>
To: Pavel Reichl <preichl@redhat.com>
Cc: linux-xfs@vger.kernel.org
Subject: Re: [PATCH v11 4/4] xfs: replace mrlock_t with rw_semaphores
Date: Tue, 13 Oct 2020 09:49:57 -0400 [thread overview]
Message-ID: <20201013134957.GG966478@bfoster> (raw)
In-Reply-To: <d780c465-a305-c3d2-e583-82d70a1f964e@redhat.com>
On Tue, Oct 13, 2020 at 03:39:03PM +0200, Pavel Reichl wrote:
>
>
> On 10/13/20 1:04 PM, Brian Foster wrote:
> > On Mon, Oct 12, 2020 at 10:44:38PM +0200, Pavel Reichl wrote:
> >>
> >>
> >> On 10/12/20 6:04 PM, Brian Foster wrote:
> >>> ...
> >>>> @@ -2863,8 +2875,20 @@ xfs_btree_split(
> >>>> args.done = &done;
> >>>> args.kswapd = current_is_kswapd();
> >>>> INIT_WORK_ONSTACK(&args.work, xfs_btree_split_worker);
> >>>> + /*
> >>>> + * Update lockdep's ownership information to reflect that we
> >>>> + * will be transferring the ilock from this thread to the
> >>>> + * worker.
> >>>> + */
> >>>
> >>> Can we update this comment to explain why we need to do this? E.g., I'm
> >>> assuming there's a lockdep splat somewhere down in the split worker
> >>> without it, but it's not immediately clear where and so it might not be
> >>> obvious if we're ever able to remove this.
> >>
> >> Hi, would something like this work for you?
> >>
> >> /*
> >> + * Update lockdep's ownership information to reflect that we
> >> + * will be transferring the ilock from this thread to the
> >> + * worker (xfs_btree_split_worker() run via queue_work()).
> >> + * If the ownership transfer would not happen lockdep would
> >> + * assert in the worker thread because the ilock would be owned
> >> + * by the original thread.
> >> + */
> >>
> >
> > That doesn't really answer the question. Do you have a record of the
> > lockdep error message that occurs without this state transfer, by
> > chance?
> >
> > Brian
>
> Hi, please see this mail from Darrick - he hit the issue first - http://mail.spinics.net/lists/linux-xfs/msg38967.html
>
Ah, I see.. thanks. I was thinking there was some kind of lock imbalance
warning or something, but in reality I think something like the
following is sufficient:
"Update lockdep's ownership information to reflect transfer of the ilock
from the current task to the worker. Otherwise assertions that the lock
is held (such as when logging the inode) might fail due to incorrect
task owner state."
Brian
> >
> >>
> >
>
next prev parent reply other threads:[~2020-10-13 13:50 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-09 19:55 [PATCH v11 0/4] xfs: Remove wrappers for some semaphores Pavel Reichl
2020-10-09 19:55 ` [PATCH v11 1/4] xfs: Refactor xfs_isilocked() Pavel Reichl
2020-10-12 16:03 ` Brian Foster
2020-10-12 21:28 ` Darrick J. Wong
2020-10-13 11:04 ` Brian Foster
2020-10-14 21:04 ` Pavel Reichl
2020-10-15 10:32 ` Brian Foster
2020-10-15 8:20 ` Christoph Hellwig
2020-10-09 19:55 ` [PATCH v11 2/4] xfs: clean up whitespace in xfs_isilocked() calls Pavel Reichl
2020-10-12 16:03 ` Brian Foster
2020-10-15 8:17 ` Christoph Hellwig
2020-10-09 19:55 ` [PATCH v11 3/4] xfs: xfs_isilocked() can only check a single lock type Pavel Reichl
2020-10-12 16:03 ` Brian Foster
2020-10-15 8:17 ` Christoph Hellwig
2020-10-09 19:55 ` [PATCH v11 4/4] xfs: replace mrlock_t with rw_semaphores Pavel Reichl
2020-10-12 16:04 ` Brian Foster
2020-10-12 20:44 ` Pavel Reichl
2020-10-13 11:04 ` Brian Foster
2020-10-13 13:39 ` Pavel Reichl
2020-10-13 13:49 ` Brian Foster [this message]
2020-10-12 21:02 ` Pavel Reichl
2020-10-12 21:30 ` Darrick J. Wong
2020-10-13 11:07 ` Brian Foster
2020-10-15 8:21 ` Christoph Hellwig
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