Messages in this thread | | | Date | Wed, 28 Oct 2015 09:33:53 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH tip/core/rcu 11/13] rculist: Make list_entry_rcu() use lockless_dereference() |
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* 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?
Thanks,
Ingo
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