From: Keith Busch <kbusch@kernel.org>
To: Hannes Reinecke <hare@suse.de>
Cc: Daniel Wagner <dwagner@suse.de>,
James Smart <james.smart@broadcom.com>,
Christoph Hellwig <hch@lst.de>,
linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 12/12] nvmet-fc: use RCU list iterator for assoc_list
Date: Tue, 6 Feb 2024 11:22:49 -0800 [thread overview]
Message-ID: <ZcKHCXtXWVCdi9Ae@kbusch-mbp.mynextlight.net> (raw)
In-Reply-To: <b19e0b0f-6b1c-4126-931b-d7b0d01fb3da@suse.de>
On Tue, Feb 06, 2024 at 02:51:24PM +0900, Hannes Reinecke wrote:
> On 1/31/24 16:51, Daniel Wagner wrote:
> > + rcu_read_lock();
> > + if (!nvmet_fc_assoc_exits(tgtport, ran)) {
> > assoc->association_id = ran;
> > list_add_tail_rcu(&assoc->a_list, &tgtport->assoc_list);
> > + done = true;
> > }
> > + rcu_read_unlock();
> > spin_unlock_irqrestore(&tgtport->lock, flags);
>
> Odd. You already take the tgtport lock, so there really is no point in using
> rcu_read_lock() here.
That's a interesting point, but I think it's harmless since there's no
rcu sync within the read section.
https://www.kernel.org/doc/Documentation/RCU/Design/Requirements/Requirements.html#Guaranteed%20Read-to-Write%20Upgrade
That said, the rcu_read_lock() seems like it should be moved to
nvmet_fc_assoc_exits() since that's the only part reading rcu protected
structures.
next prev parent reply other threads:[~2024-02-06 19:22 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-31 8:51 [PATCH v5 00/12] enable nvmet-fc for blktests Daniel Wagner
2024-01-31 8:51 ` [PATCH v5 01/12] nvme-fc: do not wait in vain when unloading module Daniel Wagner
2024-02-01 12:41 ` Hannes Reinecke
2024-01-31 8:51 ` [PATCH v5 02/12] nvmet-fcloop: swap the list_add_tail arguments Daniel Wagner
2024-02-01 12:42 ` Hannes Reinecke
2024-01-31 8:51 ` [PATCH v5 03/12] nvmet-fc: release reference on target port Daniel Wagner
2024-01-31 8:51 ` [PATCH v5 04/12] nvmet-fc: defer cleanup using RCU properly Daniel Wagner
2024-02-01 12:43 ` Hannes Reinecke
2024-01-31 8:51 ` [PATCH v5 05/12] nvmet-fc: free queue and assoc directly Daniel Wagner
2024-01-31 8:51 ` [PATCH v5 06/12] nvmet-fc: hold reference on hostport match Daniel Wagner
2024-01-31 8:51 ` [PATCH v5 07/12] nvmet-fc: remove null hostport pointer check Daniel Wagner
2024-01-31 8:51 ` [PATCH v5 08/12] nvmet-fc: do not tack refs on tgtports from assoc Daniel Wagner
2024-01-31 8:51 ` [PATCH v5 09/12] nvmet-fc: abort command when there is no binding Daniel Wagner
2024-01-31 8:51 ` [PATCH v5 10/12] nvmet-fc: avoid deadlock on delete association path Daniel Wagner
2024-02-06 3:03 ` Hannes Reinecke
2024-01-31 8:51 ` [PATCH v5 11/12] nvmet-fc: take ref count on tgtport before delete assoc Daniel Wagner
2024-02-06 5:47 ` Hannes Reinecke
2024-01-31 8:51 ` [PATCH v5 12/12] nvmet-fc: use RCU list iterator for assoc_list Daniel Wagner
2024-01-31 17:31 ` Christoph Hellwig
2024-02-06 5:51 ` Hannes Reinecke
2024-02-06 19:22 ` Keith Busch [this message]
2024-02-12 10:31 ` Daniel Wagner
2024-02-01 0:28 ` [PATCH v5 00/12] enable nvmet-fc for blktests Keith Busch
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