On 08/13/13 09:43, Tejun Heo wrote: > 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?
Yes you're right. It was always racy. > >> 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()? Maybe, but I was trying to make a minimal fix here. -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation -- 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/
