* [PATCH] rcu_tree: avoid touch rnp->completed when starts a new GP
@ 2015-01-13 7:30 Lai Jiangshan
2015-01-13 9:36 ` Paul E. McKenney
0 siblings, 1 reply; 2+ messages in thread
From: Lai Jiangshan @ 2015-01-13 7:30 UTC (permalink / raw)
To: linux-kernel, Paul E. McKenney
Cc: Lai Jiangshan, Josh Triplett, Steven Rostedt, Mathieu Desnoyers
In rcu_gp_init(), rnp->completed equals to rsp->completed in THEORY,
we don't need to touch it normally. If something goes wrong,
it will complain and fixup rnp->completed and avoid oops.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
---
kernel/rcu/tree.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 7680fc2..ea6dc28 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1639,8 +1639,8 @@ static int rcu_gp_init(struct rcu_state *rsp)
rcu_preempt_check_blocked_tasks(rnp);
rnp->qsmask = rnp->qsmaskinit;
ACCESS_ONCE(rnp->gpnum) = rsp->gpnum;
- WARN_ON_ONCE(rnp->completed != rsp->completed);
- ACCESS_ONCE(rnp->completed) = rsp->completed;
+ if (WARN_ON_ONCE(rnp->completed != rsp->completed))
+ ACCESS_ONCE(rnp->completed) = rsp->completed;
if (rnp == rdp->mynode)
(void)__note_gp_changes(rsp, rnp, rdp);
rcu_preempt_boost_start_gp(rnp);
--
2.1.0
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] rcu_tree: avoid touch rnp->completed when starts a new GP
2015-01-13 7:30 [PATCH] rcu_tree: avoid touch rnp->completed when starts a new GP Lai Jiangshan
@ 2015-01-13 9:36 ` Paul E. McKenney
0 siblings, 0 replies; 2+ messages in thread
From: Paul E. McKenney @ 2015-01-13 9:36 UTC (permalink / raw)
To: Lai Jiangshan
Cc: linux-kernel, Josh Triplett, Steven Rostedt, Mathieu Desnoyers
On Tue, Jan 13, 2015 at 03:30:34PM +0800, Lai Jiangshan wrote:
> In rcu_gp_init(), rnp->completed equals to rsp->completed in THEORY,
> we don't need to touch it normally. If something goes wrong,
> it will complain and fixup rnp->completed and avoid oops.
>
> Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Queued for 3.21, thank you!
Thanx, Paul
> ---
> kernel/rcu/tree.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 7680fc2..ea6dc28 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -1639,8 +1639,8 @@ static int rcu_gp_init(struct rcu_state *rsp)
> rcu_preempt_check_blocked_tasks(rnp);
> rnp->qsmask = rnp->qsmaskinit;
> ACCESS_ONCE(rnp->gpnum) = rsp->gpnum;
> - WARN_ON_ONCE(rnp->completed != rsp->completed);
> - ACCESS_ONCE(rnp->completed) = rsp->completed;
> + if (WARN_ON_ONCE(rnp->completed != rsp->completed))
> + ACCESS_ONCE(rnp->completed) = rsp->completed;
> if (rnp == rdp->mynode)
> (void)__note_gp_changes(rsp, rnp, rdp);
> rcu_preempt_boost_start_gp(rnp);
> --
> 2.1.0
>
^ permalink raw reply [flat|nested] 2+ messages in thread
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2015-01-13 7:30 [PATCH] rcu_tree: avoid touch rnp->completed when starts a new GP Lai Jiangshan
2015-01-13 9:36 ` Paul E. McKenney
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