From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pavel Machek Subject: Re: [PATCH v2] PM / sleep: prohibit devices probing during suspend/hibernation Date: Thu, 5 Nov 2015 23:19:03 +0100 Message-ID: <20151105221903.GA4919@amd> References: <1445288064-25299-1-git-send-email-grygorii.strashko@ti.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1445288064-25299-1-git-send-email-grygorii.strashko@ti.com> Sender: linux-kernel-owner@vger.kernel.org To: Grygorii Strashko Cc: "Rafael J. Wysocki" , stern@rowland.harvard.edu, Greg Kroah-Hartman , linux-pm@vger.kernel.org, Len Brown , linux-kernel@vger.kernel.org, Thierry Reding List-Id: linux-pm@vger.kernel.org On Mon 2015-10-19 23:54:24, Grygorii Strashko wrote: > It is unsafe [1] if probing of devices will happen during suspend or > hibernation and system behavior will be unpredictable in this case > (for example: after successful probe the device potentially has a different > set of PM callbacks than before [2]). > So, let's prohibit device's probing in dpm_prepare() and defer their > probes instead. The normal behavior will be restored in dpm_complete(). > > This patch introduces new DD core APIs: > device_defer_all_probes_enable() > It will disable probing of devices and defer their probes. > device_defer_all_probes_disable() > It will restore normal behavior and trigger re-probing of deferred > devices. > > [1] https://lkml.org/lkml/2015/9/11/554 > [2] https://lkml.org/lkml/2015/9/15/1039 > Cc: Alan Stern > Cc: Rafael J. Wysocki > Cc: Thierry Reding > Signed-off-by: Grygorii Strashko > --- > Changes in v2: > - DD core API device_defer_all_probes(bool enable) split on two > void device_defer_all_probes_enable(void); > void device_defer_all_probes_disable(void); > - more comments added > > Link on v1: > - https://lkml.org/lkml/2015/10/8/681 > > drivers/base/base.h | 2 ++ > drivers/base/dd.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++- > drivers/base/power/main.c | 17 +++++++++++++++++ > 3 files changed, 66 insertions(+), 1 deletion(-) > > diff --git a/drivers/base/base.h b/drivers/base/base.h > index 1782f3a..c332b68 100644 > --- a/drivers/base/base.h > +++ b/drivers/base/base.h > @@ -131,6 +131,8 @@ extern void device_remove_groups(struct device *dev, > extern char *make_class_name(const char *name, struct kobject *kobj); > > extern int devres_release_all(struct device *dev); > +extern void device_defer_all_probes_enable(void); > +extern void device_defer_all_probes_disable(void); > > /* /sys/devices directory */ > extern struct kset *devices_kset; > diff --git a/drivers/base/dd.c b/drivers/base/dd.c > index be0eb46..b8d9e70 100644 > --- a/drivers/base/dd.c > +++ b/drivers/base/dd.c > @@ -55,6 +55,13 @@ static struct workqueue_struct *deferred_wq; > static atomic_t deferred_trigger_count = ATOMIC_INIT(0); > > /* > + * In some cases, like suspend to RAM or hibernation, It might be reasonable > + * to prohibit probing of devices as it could be unsafe. > + * Once defer_all_probes is true all drivers probes will be forcibly deferred. > + */ > +static bool defer_all_probes; > + > +/* > * deferred_probe_work_func() - Retry probing devices in the active list. > */ > static void deferred_probe_work_func(struct work_struct *work) > @@ -172,6 +179,30 @@ static void driver_deferred_probe_trigger(void) > } > > /** > + * device_defer_all_probes_enable() - Enable deferring of device's probes > + * > + * It will disable probing of devices and defer their probes. > + */ > +void device_defer_all_probes_enable(void) > +{ > + defer_all_probes = true; > + /* sync with probes to avoid races. */ > + wait_for_device_probe(); > +} device_pause_probing()? > +/** > + * device_defer_all_probes_disable() - Disable deferring of device's probes > + * > + * It will restore normal behavior and trigger re-probing of deferred > + * devices. > + */ Hmm. This is not quite a double negative... but it sounds like one. device_restart_probing()? Thanks, Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html