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PM / QoS: Fix workqueue deadlock when using pm_qos_update_request_timeout()

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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. Let's extract the little bit of code that does
the real work of pm_qos_update_request() and call it from the
work function so that we don't deadlock.

Before ed1ac6e (PM: don't use [delayed_]work_pending()) this didn't
happen because the work function wouldn't try to cancel itself.

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Reviewed-by: Tejun Heo <tj@kernel.org>
Cc: 3.9+ <stable@vger.kernel.org> # 3.9+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Stephen Boyd 2013-08-13 14:12:40 -07:00 committed by Rafael J. Wysocki
parent d4e4ab86bc
commit 40fea92ffb
1 changed files with 13 additions and 7 deletions
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20
kernel/power/qos.c
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@ -296,6 +296,17 @@ int pm_qos_request_active(struct pm_qos_request *req)
}
EXPORT_SYMBOL_GPL(pm_qos_request_active);
static void __pm_qos_update_request(struct pm_qos_request *req,
s32 new_value)
{
trace_pm_qos_update_request(req->pm_qos_class, new_value);
if (new_value != req->node.prio)
pm_qos_update_target(
pm_qos_array[req->pm_qos_class]->constraints,
&req->node, PM_QOS_UPDATE_REQ, new_value);
}
/**
* pm_qos_work_fn - the timeout handler of pm_qos_update_request_timeout
* @work: work struct for the delayed work (timeout)
@ -308,7 +319,7 @@ static void pm_qos_work_fn(struct work_struct *work)
struct pm_qos_request,
work);
pm_qos_update_request(req, PM_QOS_DEFAULT_VALUE);
__pm_qos_update_request(req, PM_QOS_DEFAULT_VALUE);
}
/**
@ -364,12 +375,7 @@ void pm_qos_update_request(struct pm_qos_request *req,
}
cancel_delayed_work_sync(&req->work);
trace_pm_qos_update_request(req->pm_qos_class, new_value);
if (new_value != req->node.prio)
pm_qos_update_target(
pm_qos_array[req->pm_qos_class]->constraints,
&req->node, PM_QOS_UPDATE_REQ, new_value);
__pm_qos_update_request(req, new_value);
}
EXPORT_SYMBOL_GPL(pm_qos_update_request);