On Tue, Sep 09, 2014 at 11:23:34AM -0700, Alex Wang wrote:
> On current master, the per-thread callback event set is flushed
> when ovsrcu_quiesce_start() is called or when the callback
> event set is full. For threads that only call 'ovsrcu_quiesce()'
> to indicate quiescient state, their callback event set will not
> be flushed for execution until the set is full. And this could
> take a very long time.
>
> Theoretically, this should not be an issue, since rcu postponed
> callback events should only free the old version of objects.
> However, current ovs does not follow this rule, and some callback
> events include other activities like unregistering the netdev
> from global name-netdev map. The delay of unregistering the netdev
> (by threads that only calls ovsrcu_quiesce()) will prevent the
> recreate of same netdev indefinitely.
>
> As a short-term workaround, this commit makes every call to
> ovsrcu_quiesce() flush the callback event set. In the long run,
> there will be a refactor of the use of ovs-rcu module, in which all
> callback events only free the old version of objects.
>
> Signed-off-by: Alex Wang <al...@nicira.com>
> ---
> lib/ovs-rcu.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/lib/ovs-rcu.c b/lib/ovs-rcu.c
> index a052d6c..6fe6103 100644
> --- a/lib/ovs-rcu.c
> +++ b/lib/ovs-rcu.c
> @@ -138,8 +138,14 @@ ovsrcu_quiesce_start(void)
> void
> ovsrcu_quiesce(void)
> {
> + struct ovsrcu_perthread *perthread;
> +
> ovsrcu_init_module();
> - ovsrcu_perthread_get()->seqno = seq_read(global_seqno);
> + perthread = pthread_getspecific(perthread_key);
> + perthread->seqno = seq_read(global_seqno);
> + if (perthread->cbset) {
> + ovsrcu_flush_cbset(perthread);
> + }
> seq_change(global_seqno);
I think that we can remove the call to ovsrcu_init_module() because
ovsrcu_perthread_get() calls it. (This was also true before your
patch.)
Acked-by: Ben Pfaff <b...@nicira.com>
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