linux-kernel - [PATCH 0/4] PM / core: Direct handling of DPM_FLAG_SMART_SUSPEND and DPM_FLAG_LEAVE

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:   Sun, 10 Dec 2017 00:55:23 +0100
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Linux PM <linux-pm@...r.kernel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alan Stern <stern@...land.harvard.edu>,
        Kevin Hilman <khilman@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Ulf Hansson <ulf.hansson@...aro.org>
Subject: [PATCH 0/4] PM / core: Direct handling of DPM_FLAG_SMART_SUSPEND and DPM_FLAG_LEAVE_SUSPENDED

Hi All,

This series is a follow-up for

https://marc.info/?l=linux-doc&m=151101644105835&w=2

Patches[1-3/6] from the above have been reviewed and agreed on, so
they are in linux-next now and here's a next version of the rest.

Patches [1-2/4] are preparatory.  The first one is just really small
code duplication avoidance on top of this recent fix:

https://patchwork.kernel.org/patch/10097563/

and the second one simply moves some code to separate functions.

Patch [3/4] causes the PM core to carry out some optimizations for
drivers of devices with DPM_FLAG_SMART_SUSPEND set whose "late"
and "noirq" suspend (or equivalent) driver callbacks are invoked
directly by the core.

The underlying observation is that if the device is suspended (via
runtime PM) during the "late suspend" phase of a system transition,
invoking the "late" and "noirq" callbacks from the driver for it is not
going to make it more suspended, so to speak, so it doesn't make sense to
invoke them at all.

[That optimization is only done for devices with DPM_FLAG_SMART_SUSPEND
set, because drivers setting that flag are expected to be prepared for
skipping their "late" and "noirq" callbacks if the device is already
suspended.]

Patch [4/4] makes the core do an analogous thing for devices with
DPM_FLAG_LEAVE_SUSPENDED set whose "noirq" and "early" resume (or
equivalent) driver callbacks are directly invoked by the core.

In that case the observation is that if such devices can be left in
suspend after the system transition to the working state, running
resume callbacks from their drivers is simply not necessary.

Pathes [3-4/4] have been reoredered and reworked a bit since the last
iteration, so they are regarded as new.

The series is on top of the linux-next branch of the linux-pm.git tree
that should be merged into linux-next on Monday.

[I have developed debug bus type and driver modules to test that code,
but they are not ready to be made available at this point.]

Thanks,
Rafael