On Tue, Feb 19, 2019 at 05:53:26PM +0100, Rafael J. Wysocki wrote: > From: Rafael J. Wysocki <[email protected]> > > Commit 4c06c4e6cf63 ("driver core: Fix possible supplier PM-usage > counter imbalance") introduced a regression that causes suppliers > to be suspended prematurely for device links added during consumer > driver probe if the initial PM-runtime status of the consumer is > "suspended" and the consumer is resumed after adding the link and > before pm_runtime_put_suppliers() is called. In that case, > pm_runtime_put_suppliers() will drop the rpm_active refcount for > the link by one and (since rpm_active is equal to two after the > preceding consumer resume) the supplier's PM-runtime usage counter > will be decremented, which may cause the supplier to suspend even > though the consumer's PM-runtime status is "active". > > For this reason, partially revert commit 4c06c4e6cf63 as the problem > it tried to fix needs to be addressed somewhat differently, and > change pm_runtime_get_suppliers() and pm_runtime_put_suppliers() so > that the latter only drops rpm_active references acquired by the > former. [This requires adding a new field to struct device_link, > but I coulnd't find a cleaner way to address the issue that would > work in all cases.] > > This causes pm_runtime_put_suppliers() to effectively ignore device > links added during consumer probe, so device_link_add() doesn't need > to worry about ensuring that suppliers will remain active after > pm_runtime_put_suppliers() for links created with DL_FLAG_RPM_ACTIVE > set and it only needs to bump up rpm_active by one for those links, > so pm_runtime_active_link() is not necessary any more. > > Fixes: 4c06c4e6cf63 ("driver core: Fix possible supplier PM-usage counter > imbalance") > Reported-by: Jon Hunter <[email protected]> > Tested-by: Jon Hunter <[email protected]> > Tested-by: Ulf Hansson <[email protected]> > Reviewed-by: Ulf Hansson <[email protected]> > Signed-off-by: Rafael J. Wysocki <[email protected]> > --- > > Changes from the RFC version: > - T-by and R-by tags from Jon and Ulf. > - More details in the changelog. > > --- > drivers/base/core.c | 4 ++-- > drivers/base/power/runtime.c | 29 ++++++----------------------- > include/linux/device.h | 1 + > include/linux/pm_runtime.h | 4 ---- > 4 files changed, 9 insertions(+), 29 deletions(-)
I'm sure Jon and Ulf have done much more extensive testing, but I've had this applied for most of today and haven't run into any issues, so: Tested-by: Thierry Reding <[email protected]>
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