Like commit c4f135d643823a86 ("workqueue: Wrap flush_workqueue() using a
macro") says, flush_scheduled_work() is dangerous and will be forbidden.
We are on the way for removing all flush_scheduled_work() callers from
the kernel, and this patch is for removing flush_scheduled_work() call
from cadence driver.
Since cdns-mhdp8546 driver uses 4 works
mhdp->modeset_retry_work
mhdp->hpd_work
mhdp->hdcp.check_work
mhdp->hdcp.prop_work
I assume that flush_scheduled_work() in cdns_mhdp_remove() needs to wait
for only these 4 works.
Since mhdp->modeset_retry_work already uses cancel_work_sync(), I assume
that flush_scheduled_work() needs to wait for only 3 works. But I came to
wonder whether mhdp->hdcp.check_work should be flushed or cancelled.
While flush_scheduled_work() waits for completion of works which were
already queued to system_wq, mhdp->hdcp.check_work is a delayed work.
That is, this work won't be queued to system_wq unless timeout expires.
Current code will wait for mhdp->hdcp.check_work only if timeout already
expired. If timeout is not expired yet, flush_scheduled_work() will fail
to cancel mhdp->hdcp.check_work, and cdns_mhdp_hdcp_check_work() which is
triggered by mhdp->hdcp.check_work will schedule hdcp->check_work, which
is too late for flush_scheduled_work() to wait for completion of
cdns_mhdp_hdcp_prop_work().
But since I couldn't get comments on how do we want to handle this race
window [1], this patch chose "do nothing" for mhdp->hdcp.check_work and
mhdp->hdcp.prop_work. That is, I assume that flush_scheduled_work() in
cdns_mhdp_remove() needs to wait for only mhdp->hpd_work work.
Link: https://lkml.kernel.org/r/943273cb-c2ec-24e3-5edb-64eacc6e2d30@xxxxxxxxxxxxxxxxxxx [1]
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
index ab63e7b11944..31442a922502 100644
--- a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
+++ b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
@@ -2605,7 +2605,8 @@ static int cdns_mhdp_remove(struct platform_device *pdev)
pm_runtime_disable(&pdev->dev);
cancel_work_sync(&mhdp->modeset_retry_work);
- flush_scheduled_work();
+ flush_work(&mhdp->hpd_work);
+ /* Ignoring mhdp->hdcp.check_work and mhdp->hdcp.prop_work here. */
clk_disable_unprepare(mhdp->clk);
--
2.18.4
