linux-kernel - Re: [PATCH] PM / wakeirq: report wakeup events in dedicated wake-IRQs

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]

Date:   Fri, 11 Nov 2016 08:31:48 -0800
From:   Tony Lindgren <tony@...mide.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Brian Norris <briannorris@...omium.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Brian Norris <computersforpeace@...il.com>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>
Subject: Re: [PATCH] PM / wakeirq: report wakeup events in dedicated wake-IRQs

* Rafael J. Wysocki <rafael@...nel.org> [161110 16:06]:
> On Thu, Nov 10, 2016 at 7:49 PM, Brian Norris <briannorris@...omium.org> wrote:
> > On Thu, Nov 10, 2016 at 10:13:55AM -0800, Dmitry Torokhov wrote:
> >> On Thu, Nov 10, 2016 at 10:07 AM, Brian Norris <briannorris@...omium.org> wrote:
> >> > It's important that user space can figure out what device woke the
> >> > system from suspend -- e.g., for debugging, or for implementing
> >> > conditional wake behavior. Dedicated wakeup IRQs don't currently do
> >> > that.
> >> >
> >> > Let's report the event (pm_wakeup_event()) and also allow drivers to
> >> > synchronize with these events in their resume path (hence, disable_irq()
> >> > instead of disable_irq_nosync()).
> >>
> >> Hmm, dev_pm_disable_wake_irq() is called from
> >> rpm_suspend()/rpm_resume() that take dev->power.lock spinlock and
> >> disable interrupts. Dropping _nosync() feels dangerous.
> >
> > Indeed. So how do you suggest we get sane wakeup reports? Every device
> > or bus that's going to use the dedicated wake APIs has to
> > synchronize_irq() [1] in their resume() routine? Seems like an odd
> > implementation detail to have to remember (and therefore most drivers
> > will get it wrong).
> >
> > Brian
> >
> > [1] Or maybe at least create a helper API that will extract the
> > dedicated wake IRQ number and do the synchronize_irq() for us, so
> > drivers don't have to stash this separately (or poke at
> > dev->power.wakeirq->irq) for no good reason.
> 
> Well, in the first place, can anyone please refresh my memory on why
> it is necessary to call dev_pm_disable_wake_irq() under power.lock?

I guess no other reason except we need to manage the wakeirq
for rpm_callback(). So we dev_pm_enable_wake_irq() before
rpm_callback() in rpm_suspend(), then disable on resume.

Regards,

Tony