From: Patrick Marlier <patrick.marlier@gmail.com>
To: Ingo Molnar <mingo@kernel.org>, Tejun Heo <tj@kernel.org>
Cc: "Linus Torvalds" <torvalds@linux-foundation.org>,
"Paul McKenney" <paulmck@linux.vnet.ibm.com>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
"Lai Jiangshan" <jiangshanlai@gmail.com>,
"Dipankar Sarma" <dipankar@in.ibm.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Mathieu Desnoyers" <mathieu.desnoyers@efficios.com>,
"Josh Triplett" <josh@joshtriplett.org>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Peter Zijlstra" <peterz@infradead.org>,
"Steven Rostedt" <rostedt@goodmis.org>,
"David Howells" <dhowells@redhat.com>,
"Eric Dumazet" <edumazet@google.com>,
"Darren Hart" <dvhart@linux.intel.com>,
"Frédéric Weisbecker" <fweisbec@gmail.com>,
"Oleg Nesterov" <oleg@redhat.com>,
"pranith kumar" <bobby.prani@gmail.com>
Subject: Re: [PATCH tip/core/rcu 11/13] rculist: Make list_entry_rcu() use lockless_dereference()
Date: Wed, 28 Oct 2015 21:35:42 +0100 [thread overview]
Message-ID: <5631319E.5000606@gmail.com> (raw)
In-Reply-To: <20151028083353.GA824@gmail.com>
On 10/28/2015 09:33 AM, Ingo Molnar wrote:
>
> * Tejun Heo <tj@kernel.org> wrote:
>
>> Subject: writeback: don't use list_entry_rcu() for pointer offsetting in bdi_split_work_to_wbs()
>>
>> bdi_split_work_to_wbs() uses list_for_each_entry_rcu_continue() to
>> walk @bdi->wb_list. To set up the initial iteration condition, it
>> uses list_entry_rcu() to calculate the entry pointer corresponding to
>> the list head; however, this isn't an actual RCU dereference and using
>> list_entry_rcu() for it ended up breaking a proposed list_entry_rcu()
>> change because it was feeding an non-lvalue pointer into the macro.
>>
>> Don't use the RCU variant for simple pointer offsetting. Use
>> list_entry() instead.
>>
>> Signed-off-by: Tejun Heo <tj@kernel.org>
>> ---
>> fs/fs-writeback.c | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
>> index 29e4599..7378169 100644
>> --- a/fs/fs-writeback.c
>> +++ b/fs/fs-writeback.c
>> @@ -779,8 +779,8 @@ static void bdi_split_work_to_wbs(struct backing_dev_info *bdi,
>> bool skip_if_busy)
>> {
>> struct bdi_writeback *last_wb = NULL;
>> - struct bdi_writeback *wb = list_entry_rcu(&bdi->wb_list,
>> - struct bdi_writeback, bdi_node);
>> + struct bdi_writeback *wb = list_entry(&bdi->wb_list,
>> + struct bdi_writeback, bdi_node);
>>
>> might_sleep();
>
> Any objections against me applying this fix to tip:core/rcu so that I can push the
> recent RCU changes towards linux-next without triggering a build failure?
No objection on my side but probably you are waiting for an ack from
somebody else.
--
Pat
next prev parent reply other threads:[~2015-10-28 20:35 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-06 16:13 [PATCH tip/core/rcu 0/13] Miscellaneous fixes for 4.4 Paul E. McKenney
2015-10-06 16:13 ` [PATCH tip/core/rcu 01/13] sched: Export sched_setscheduler_nocheck Paul E. McKenney
2015-10-06 16:13 ` [PATCH tip/core/rcu 02/13] rcu: Use rcu_callback_t in call_rcu*() and friends Paul E. McKenney
2015-10-06 16:13 ` [PATCH tip/core/rcu 03/13] rcu: Use call_rcu_func_t to replace explicit type equivalents Paul E. McKenney
2015-10-06 16:13 ` [PATCH tip/core/rcu 04/13] rcu: Don't disable preemption for Tiny and Tree RCU readers Paul E. McKenney
2015-10-06 16:20 ` [Kernel networking modules.] OSI levels 2 & 3, Assistance - If anyone knows anyone in the US. North West region John D Allen, Leveridge Systems INC
2015-10-06 16:44 ` [PATCH tip/core/rcu 04/13] rcu: Don't disable preemption for Tiny and Tree RCU readers Josh Triplett
2015-10-06 17:01 ` Paul E. McKenney
2015-10-06 17:16 ` Josh Triplett
2015-10-06 17:42 ` Paul E. McKenney
2015-10-06 17:46 ` Josh Triplett
2015-10-06 20:05 ` Peter Zijlstra
2015-10-06 20:18 ` Paul E. McKenney
2015-10-06 20:52 ` Peter Zijlstra
2015-10-06 21:05 ` Paul E. McKenney
2015-10-07 7:19 ` Peter Zijlstra
2015-10-06 16:13 ` [PATCH tip/core/rcu 05/13] rcu: Eliminate panic when silly boot-time fanout specified Paul E. McKenney
2015-10-06 16:13 ` [PATCH tip/core/rcu 06/13] rcu: Add online/offline info to stall warning message Paul E. McKenney
2015-10-06 17:15 ` Josh Triplett
2015-10-06 16:13 ` [PATCH tip/core/rcu 07/13] rcu: Move preemption disabling out of __srcu_read_lock() Paul E. McKenney
2015-10-06 17:18 ` Josh Triplett
2015-10-06 17:36 ` Paul E. McKenney
2015-10-06 17:43 ` Josh Triplett
2015-10-06 18:07 ` Paul E. McKenney
2015-10-06 20:07 ` Peter Zijlstra
2015-10-06 20:19 ` Paul E. McKenney
2015-10-06 20:32 ` Peter Zijlstra
2015-10-06 21:03 ` Paul E. McKenney
2015-10-07 7:20 ` Peter Zijlstra
2015-10-07 14:18 ` Paul E. McKenney
2015-10-06 16:13 ` [PATCH tip/core/rcu 08/13] rcu: Finish folding ->fqs_state into ->gp_state Paul E. McKenney
2015-10-06 16:13 ` [PATCH tip/core/rcu 09/13] rcu: Correct comment for values of ->gp_state field Paul E. McKenney
2015-10-06 16:13 ` [PATCH tip/core/rcu 10/13] rcu: Add rcu_pointer_handoff() Paul E. McKenney
2015-10-06 17:21 ` Josh Triplett
2015-10-06 17:31 ` Paul E. McKenney
2015-10-06 17:36 ` Josh Triplett
2015-10-06 20:27 ` Peter Zijlstra
2015-10-06 21:02 ` Paul E. McKenney
2015-10-07 7:22 ` Peter Zijlstra
2015-10-07 14:20 ` Paul E. McKenney
2015-10-06 16:13 ` [PATCH tip/core/rcu 11/13] rculist: Make list_entry_rcu() use lockless_dereference() Paul E. McKenney
2015-10-26 8:45 ` Ingo Molnar
2015-10-26 14:55 ` Paul E. McKenney
2015-10-26 18:02 ` Ingo Molnar
2015-10-27 3:37 ` Linus Torvalds
2015-10-27 5:19 ` Tejun Heo
2015-10-27 5:33 ` Paul E. McKenney
2015-10-28 8:33 ` Ingo Molnar
2015-10-28 20:35 ` Patrick Marlier [this message]
2015-10-29 0:00 ` Paul E. McKenney
2015-10-29 2:13 ` Tejun Heo
2015-10-28 20:58 ` [tip:core/rcu] fs/writeback, rcu: Don't use list_entry_rcu() for pointer offsetting in bdi_split_work_to_wbs() tip-bot for Tejun Heo
2015-10-27 5:32 ` [PATCH tip/core/rcu 11/13] rculist: Make list_entry_rcu() use lockless_dereference() Paul E. McKenney
2015-10-06 16:13 ` [PATCH tip/core/rcu 12/13] rcu: Remove deprecated rcu_lockdep_assert() Paul E. McKenney
2015-10-06 16:13 ` [PATCH tip/core/rcu 13/13] rculist: Use WRITE_ONCE() when deleting from reader-visible list Paul E. McKenney
2015-10-06 17:23 ` [PATCH tip/core/rcu 0/13] Miscellaneous fixes for 4.4 Josh Triplett
2015-10-06 17:38 ` Paul E. McKenney
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