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Rajat Jain 32f733a8f4 PM / s2idle: Clear the events_check_enabled flag 
[ Upstream commit 95b982b451 ]

Problem: This flag does not get cleared currently in the suspend or
resume path in the following cases:

 * In case some driver's suspend routine returns an error.
 * Successful s2idle case
 * etc?

Why is this a problem: What happens is that the next suspend attempt
could fail even though the user did not enable the flag by writing to
/sys/power/wakeup_count. This is 1 use case how the issue can be seen
(but similar use case with driver suspend failure can be thought of):

 1. Read /sys/power/wakeup_count
 2. echo count > /sys/power/wakeup_count
 3. echo freeze > /sys/power/wakeup_count
 4. Let the system suspend, and wakeup the system using some wake source
    that calls pm_wakeup_event() e.g. power button or something.
 5. Note that the combined wakeup count would be incremented due
    to the pm_wakeup_event() in the resume path.
 6. After resuming the events_check_enabled flag is still set.

At this point if the user attempts to freeze again (without writing to
/sys/power/wakeup_count), the suspend would fail even though there has
been no wake event since the past resume.

Address that by clearing the flag just before a resume is completed,
so that it is always cleared for the corner cases mentioned above.

Signed-off-by: Rajat Jain <rajatja@google.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2017-12-20 10:10:23 +01:00
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README 

Linux kernel
============

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.