From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Josh Triplett <josh@joshtriplett.org>
Cc: NeilBrown <neilb@suse.com>,
Trond Myklebust <trond.myklebust@primarydata.com>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Anna Schumaker <anna.schumaker@netapp.com>,
linux-nfs@vger.kernel.org, Lai Jiangshan <jiangshanlai@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/4] rculist: add list_for_each_entry_from_rcu()
Date: Mon, 30 Apr 2018 06:43:08 -0700 [thread overview]
Message-ID: <20180430134308.GT26088@linux.vnet.ibm.com> (raw)
In-Reply-To: <20180430052032.GA16963@localhost>
On Sun, Apr 29, 2018 at 10:20:33PM -0700, Josh Triplett wrote:
> On Mon, Apr 30, 2018 at 02:31:30PM +1000, NeilBrown wrote:
> > list_for_each_entry_from_rcu() is an RCU version of
> > list_for_each_entry_from(). It walks a linked list under rcu
> > protection, from a given start point.
> >
> > It is similar to list_for_each_entry_continue_rcu() but starts *at*
> > the given position rather than *after* it.
> >
> > Naturally, the start point must be known to be in the list.
>
> I'd suggest giving an explicit advisory comment to clarify and suggest
> correct usage:
>
> "This would typically require either that you obtained the node from a
> previous walk of the list in the same RCU read-side critical section, or
> that you held some sort of non-RCU reference (such as a reference count)
> to keep the node alive *and* in the list."
>
> (Feel free to wordsmith the exact wording, but something like that seems
> like it would help people understand how to use this correctly, and make
> it less likely that they'd use it incorrectly.)
What Josh said! Could you also contrast this with the existing
list_for_each_entry_continue_rcu() macro in the header comment as well
as in the commit log?
Thanx, Paul
next prev parent reply other threads:[~2018-04-30 13:41 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-30 4:31 [PATCH 0/4 V2] Avoid quadratic search when freeing delegations NeilBrown
2018-04-30 4:31 ` [PATCH 3/4] rculist: add list_for_each_entry_from_rcu() NeilBrown
2018-04-30 5:20 ` Josh Triplett
2018-04-30 13:43 ` Paul E. McKenney [this message]
2018-04-30 15:14 ` Steven Rostedt
2018-04-30 15:35 ` Paul E. McKenney
2018-05-01 3:11 ` [PATCH 3/4 v2] " NeilBrown
2018-05-01 14:14 ` Paul E. McKenney
2018-05-01 21:34 ` NeilBrown
2018-04-30 4:31 ` [PATCH 1/4] NFS: slight optimization for walking list for delegations NeilBrown
2018-04-30 15:17 ` Steven Rostedt
2018-05-31 5:23 ` [PATCH 1/4 v2] " NeilBrown
2018-06-04 21:31 ` Steven Rostedt
2018-04-30 4:31 ` [PATCH 2/4] NFS: use cond_resched() when restarting walk of delegation list NeilBrown
2018-04-30 4:31 ` [PATCH 4/4] NFS: Avoid quadratic search when freeing delegations NeilBrown
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