From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thierry Reding Subject: Re: [PATCH] driver core: Fix PM-runtime for links added during consumer probe Date: Tue, 19 Feb 2019 18:07:04 +0100 Message-ID: <20190219170704.GB14351@ulmo> References: <2442421.P6CTj2BjBs@aspire.rjw.lan> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="XOIedfhf+7KOe/yw" Return-path: Content-Disposition: inline In-Reply-To: <2442421.P6CTj2BjBs@aspire.rjw.lan> Sender: linux-kernel-owner@vger.kernel.org To: "Rafael J. Wysocki" Cc: Greg Kroah-Hartman , Ulf Hansson , Jon Hunter , LKML , Linux PM , Daniel Vetter , Lukas Wunner , Andrzej Hajda , Russell King - ARM Linux , Lucas Stach , Linus Walleij , Laurent Pinchart , Marek Szyprowski List-Id: linux-pm@vger.kernel.org --XOIedfhf+7KOe/yw Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Feb 19, 2019 at 05:53:26PM +0100, Rafael J. Wysocki wrote: > From: Rafael J. Wysocki >=20 > 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". >=20 > 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.] >=20 > 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. >=20 > Fixes: 4c06c4e6cf63 ("driver core: Fix possible supplier PM-usage counter= imbalance") > Reported-by: Jon Hunter > Tested-by: Jon Hunter > Tested-by: Ulf Hansson > Reviewed-by: Ulf Hansson > Signed-off-by: Rafael J. Wysocki > --- >=20 > Changes from the RFC version: > - T-by and R-by tags from Jon and Ulf. > - More details in the changelog. >=20 > --- > 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 --XOIedfhf+7KOe/yw Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCAAdFiEEiOrDCAFJzPfAjcif3SOs138+s6EFAlxsN7gACgkQ3SOs138+ s6Fm+xAAnvoSqdn6wZcWkWeG6qooOo7YeCJH5FRW4fU6hIXoj6So8VgX9Miqnn+j bDvvgviE6euyVqHSA2gokG35z0JQE8ZrIBcVwx2nZ7Qk8tGpYncvDtnnXCarnY6p z4tfFrLK15/c84R1tc/ighFWS+9HAdZ33Lp673bhKCioGS52oUKoHKPIfoSYzIhL oHcby4bCaWz91vwHVWfIF8vsBzvVPfs784D5Pc/nObvfOpa61ec1QkZvt+sdsC6L edN63P4bYUzFhASWyrsOSPDomahh535L1cnXnNObcZTIIeOigiI6/gMDAhQkHK6E QV6KtIPvj/uooTj9WHT5RqGHhQb+6fcyOzVwsJMJLpAdqErOzBTVlw1j1IuvGu2q uOu1n+pz0c3h2y0B1bRc+CWjEMvRoHYz+eIcfE6GNk9oA1oE2rmiO4K/OeNicbew hVrAuwBj02PgFmvEyfk9te08jhWwPEdApQB6A1bOazF+HHp/sHF/18F/1zochBcO 2hiyTs8br4Sriv2f+AnYncGTEGGgTtcDI5006mut0QlKTkTJT03PNEpP4I8aKtic rrAfRIQbDA2BN6qcaBbjvAtgPZ6kVCRMcGBfp/yGg1fFh+6zbrROChQsiXrbbnDO PLgh+vZMsUpj2QjwLbWCfl9+5ye6vIMX+FeFXSDIkjzWZetK2dY= =hcNP -----END PGP SIGNATURE----- --XOIedfhf+7KOe/yw--