linux-kernel - Re: [RFC][PATCH 0/8] PM: Implement autosleep and "wake locks"

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

Message-ID: <CAMP5XgeqXJroKtHZO18SESFxg1iGP=wHAa+CU1zEEXQqUEQwTA@mail.gmail.com>
Date:	Mon, 13 Feb 2012 18:07:26 -0800
From:	Arve Hjønnevåg <arve@...roid.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Linux PM list <linux-pm@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Magnus Damm <magnus.damm@...il.com>, markgross@...gnar.org,
	Matthew Garrett <mjg@...hat.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	John Stultz <john.stultz@...aro.org>,
	Brian Swetland <swetland@...gle.com>,
	Neil Brown <neilb@...e.de>,
	Alan Stern <stern@...land.harvard.edu>
Subject: Re: [RFC][PATCH 0/8] PM: Implement autosleep and "wake locks"

On Mon, Feb 6, 2012 at 5:00 PM, Rafael J. Wysocki <rjw@...k.pl> wrote:
...
> All in all, it's not as much code as I thought it would be and it seems to be
> relatively simple (which rises the question why the Android people didn't
> even _try_ to do something like this instead of slapping the "real" wakelocks
> onto the kernel FWIW).  IMHO it doesn't add anything really new to the kernel,
> except for the user space interfaces that should be maintainable.  At least I
> think I should be able to maintain them. :-)
>

Replacing a working solution with an untested one takes time. That
said, I have recently tried replacing all our kernel wake-locks with a
thin wrapper around wake-sources. This appears to mostly work, but the
wake-source timeout feature has some bugs or incompatible apis. An
init api would also be useful for embedding wake-sources in other data
structures without adding another memory allocation. Your patch to
move the spinlock init to wakeup_source_add still require the struct
to be zero initialized and the name set manually.

I needed to use two wake-sources per wake-lock since calling
__pm_stay_awake after __pm_wakeup_event on a wake-source does not
cancel the timeout. Unless there is a reason to keep this behavior I
would like __pm_stay_awake to cancel any active timeout.

Destroying a wake-source also has some problems. If you call
wakeup_source_destroy it will spin forever if the wake-source is
active without a timeout. And, if you call __pm_relax then
wakeup_source_destroy it could free the wake-source memory while the
timer function is still running. It also looks as if the wake_source
can be immediately deactivated if you call __pm_wakeup_event at the
same time as the previous timeout expired.

-- 
Arve Hjønnevåg
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/