Hello, Stephen. On Thu, Aug 08, 2013 at 01:13:57PM -0700, Stephen Boyd wrote: > pm_qos_update_request_timeout() updates a qos and then schedules > a delayed work item to bring the qos back down to the default > after the timeout. When the work item runs, pm_qos_work_fn() will > call pm_qos_update_request() and deadlock because it tries to > cancel itself via cancel_delayed_work_sync(). Future callers of > that qos will also hang waiting to cancel the work that is > canceling itself. Before ed1ac6e (PM: don't use > [delayed_]work_pending(), 2013-01-11) this didn't happen because > the work function wouldn't try to cancel itself.
I see. That must have been racy tho. If the work item execution races someone else queuing the work item, the same deadlock could happen, right? > Let's just do the little bit of pm_qos_update_request() here so > that we don't deadlock. > > Cc: Tejun Heo <t...@kernel.org> > Signed-off-by: Stephen Boyd <sb...@codeaurora.org> > --- > kernel/power/qos.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/kernel/power/qos.c b/kernel/power/qos.c > index 06fe285..d52d314 100644 > --- a/kernel/power/qos.c > +++ b/kernel/power/qos.c > @@ -308,7 +308,11 @@ static void pm_qos_work_fn(struct work_struct *work) > struct pm_qos_request, > work); > > - pm_qos_update_request(req, PM_QOS_DEFAULT_VALUE); > + if (PM_QOS_DEFAULT_VALUE != req->node.prio) > + pm_qos_update_target( > + pm_qos_array[req->pm_qos_class]->constraints, > + &req->node, PM_QOS_UPDATE_REQ, > + PM_QOS_DEFAULT_VALUE); Maybe it'd be cleaner to add a param or internal variant of pm_qos_update_request()? Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
