From: "Rafael J. Wysocki" <email@example.com> To: Ulf Hansson <firstname.lastname@example.org> Cc: "Rafael J. Wysocki" <email@example.com>, Jon Hunter <firstname.lastname@example.org>, Greg Kroah-Hartman <email@example.com>, LKML <firstname.lastname@example.org>, Linux PM <email@example.com>, Daniel Vetter <firstname.lastname@example.org>, Lukas Wunner <email@example.com>, Andrzej Hajda <firstname.lastname@example.org>, Russell King - ARM Linux <email@example.com>, Lucas Stach <firstname.lastname@example.org>, Linus Walleij <email@example.com>, Thierry Reding <firstname.lastname@example.org>, Laurent Pinchart <email@example.com>, Marek Szyprowski <firstname.lastname@example.org> Subject: Re: [RFT/RFC][PATCH] driver core: Fix PM-runtime for links added during consumer probe Date: Tue, 19 Feb 2019 17:16:18 +0100 [thread overview] Message-ID: <CAJZ5v0gm_eKm4FdJUbuwaZwxoWWoHk0BwH25tpQj+9xrgV7zuA@mail.gmail.com> (raw) In-Reply-To: <CAPDyKFrZ8Miy9A2wFksJLxePk+O05NtEmf58Q-8BqDdZ7kL7AQ@mail.gmail.com> On Tue, Feb 19, 2019 at 1:10 PM Ulf Hansson <email@example.com> wrote: > > On Mon, 18 Feb 2019 at 23:09, Rafael J. Wysocki <firstname.lastname@example.org> wrote: > > > > From: Rafael J. Wysocki <email@example.com> > > > > 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". > > Just to confirm, this is the behavior that I see as well. > > However, I am a bit a surprised on my side, that I did not run this > particular test sequence earlier. Sorry about that! > > > > > 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.] > > > > Fixes: 4c06c4e6cf63 ("driver core: Fix possible supplier PM-usage counter imbalance") > > Reported-by: Jon Hunter <firstname.lastname@example.org> > > Signed-off-by: Rafael J. Wysocki <email@example.com> > > Besides validating the fix, I can confirm device link add/removal > during probe works fine, as before. > > I also tested the runtime PM autosuspend (several seconds timeout) > together with DL_FLAG_RPM_ACTIVE - it's working fine! During this > test, the rpm_active count reaches 3 after probe and the supplier's > usage count reaches 2. When the consumer becomes runtime suspended, > after the timeout, these "counts" becomes decremented to 1 and 0, so > the supplier also becomes runtime suspended. > > Tested-by: Ulf Hansson <firstname.lastname@example.org> > Reviewed-by: Ulf Hansson <email@example.com> Many thanks to you and Jon for verifying it!
prev parent reply other threads:[~2019-02-19 16:16 UTC|newest] Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-02-18 22:08 Rafael J. Wysocki 2019-02-19 10:24 ` Jon Hunter 2019-02-19 12:10 ` Ulf Hansson 2019-02-19 16:16 ` Rafael J. Wysocki [this message]
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