| Message ID | 20180708003256.15655-1-javierm@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Sun, Jul 08, 2018 at 02:32:56AM +0200, Javier Martinez Canillas wrote: > With Device Trees (DT), the dependencies of the devices are defined in the > DT, then the drivers parse that information to lookup the needed resources > that have as dependencies. > > Since drivers and devices are registered in a non-deterministic way, it is > possible that a device that is a dependency has not been registered yet by > the time that is looked up. > > In this case the driver that requires this dependency cannot probe and has > to defer it. So the driver core adds it to a list of deferred devices that > is iterated again every time that a new driver is probed successfully. > > For debugging purposes it may be useful to know what are the devices whose > probe function was deferred. Add a debugfs entry showing that information. > > $ cat /sys/kernel/debug/devices_deferred > 48070000.i2c:twl@48:bci > musb-hdrc.0.auto > omapdrm.0 > > This information could be obtained partially by enabling debugging, but it > means that the kernel log has to be parsed and the probe deferral balanced > with the successes. This can be error probe and has to be done in a ad-hoc > manner by everyone who needs to debug these kind of issues. > > Since the information is already known by the kernel, just show it to make > it easier to debug. > > Signed-off-by: Javier Martinez Canillas <javierm@redhat.com> > Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com> > Reviewed-by: Mark Brown <broonie@kernel.org> > > --- > > Changes since RFC v1: > - Remove unneeded ret variable from deferred_devs_show() > > Changes since RFC v2: > - Use DEFINE_SHOW_ATTRIBUTE() macro. > - Don't propagate debugfs_create_file() error. > - Remove IS_ENABLED(CONFIG_DEBUG_FS) guards. > - Drop RFC prefix. > > Changes since v1: > - Better explain in the commit message why this patch is useful. > - Rename deferred_devices entry to devices_deferred. > - Add an exit function and remove the debugfs entry. > > Changes since v2: > - Add Andy Shevchenko and Mark Brown Reviewed-by tag. > - Rebase on top of Greg's driver-core-next branch. > > > drivers/base/dd.c | 30 ++++++++++++++++++++++++++++++ > 1 file changed, 30 insertions(+) > > diff --git a/drivers/base/dd.c b/drivers/base/dd.c > index 6ea9c5cece7..140f534ee9c 100644 > --- a/drivers/base/dd.c > +++ b/drivers/base/dd.c > @@ -16,6 +16,7 @@ > * Copyright (c) 2007-2009 Novell Inc. > */ > > +#include <linux/debugfs.h> > #include <linux/device.h> > #include <linux/delay.h> > #include <linux/dma-mapping.h> > @@ -53,6 +54,8 @@ static DEFINE_MUTEX(deferred_probe_mutex); > static LIST_HEAD(deferred_probe_pending_list); > static LIST_HEAD(deferred_probe_active_list); > static atomic_t deferred_trigger_count = ATOMIC_INIT(0); > +static struct dentry *deferred_devices; > +static bool initcalls_done; Wait, why add this variable? No one uses it that I can see in this patch, doesn't it create a build warning? You did test-build this, right? greg k-h
On Sun, Jul 08, 2018 at 03:21:07PM +0200, Greg Kroah-Hartman wrote: > On Sun, Jul 08, 2018 at 02:32:56AM +0200, Javier Martinez Canillas wrote: > > With Device Trees (DT), the dependencies of the devices are defined in the > > DT, then the drivers parse that information to lookup the needed resources > > that have as dependencies. > > > > Since drivers and devices are registered in a non-deterministic way, it is > > possible that a device that is a dependency has not been registered yet by > > the time that is looked up. > > > > In this case the driver that requires this dependency cannot probe and has > > to defer it. So the driver core adds it to a list of deferred devices that > > is iterated again every time that a new driver is probed successfully. > > > > For debugging purposes it may be useful to know what are the devices whose > > probe function was deferred. Add a debugfs entry showing that information. > > > > $ cat /sys/kernel/debug/devices_deferred > > 48070000.i2c:twl@48:bci > > musb-hdrc.0.auto > > omapdrm.0 > > > > This information could be obtained partially by enabling debugging, but it > > means that the kernel log has to be parsed and the probe deferral balanced > > with the successes. This can be error probe and has to be done in a ad-hoc > > manner by everyone who needs to debug these kind of issues. > > > > Since the information is already known by the kernel, just show it to make > > it easier to debug. > > > > Signed-off-by: Javier Martinez Canillas <javierm@redhat.com> > > Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com> > > Reviewed-by: Mark Brown <broonie@kernel.org> > > > > --- > > > > Changes since RFC v1: > > - Remove unneeded ret variable from deferred_devs_show() > > > > Changes since RFC v2: > > - Use DEFINE_SHOW_ATTRIBUTE() macro. > > - Don't propagate debugfs_create_file() error. > > - Remove IS_ENABLED(CONFIG_DEBUG_FS) guards. > > - Drop RFC prefix. > > > > Changes since v1: > > - Better explain in the commit message why this patch is useful. > > - Rename deferred_devices entry to devices_deferred. > > - Add an exit function and remove the debugfs entry. > > > > Changes since v2: > > - Add Andy Shevchenko and Mark Brown Reviewed-by tag. > > - Rebase on top of Greg's driver-core-next branch. > > > > > > drivers/base/dd.c | 30 ++++++++++++++++++++++++++++++ > > 1 file changed, 30 insertions(+) > > > > diff --git a/drivers/base/dd.c b/drivers/base/dd.c > > index 6ea9c5cece7..140f534ee9c 100644 > > --- a/drivers/base/dd.c > > +++ b/drivers/base/dd.c > > @@ -16,6 +16,7 @@ > > * Copyright (c) 2007-2009 Novell Inc. > > */ > > > > +#include <linux/debugfs.h> > > #include <linux/device.h> > > #include <linux/delay.h> > > #include <linux/dma-mapping.h> > > @@ -53,6 +54,8 @@ static DEFINE_MUTEX(deferred_probe_mutex); > > static LIST_HEAD(deferred_probe_pending_list); > > static LIST_HEAD(deferred_probe_active_list); > > static atomic_t deferred_trigger_count = ATOMIC_INIT(0); > > +static struct dentry *deferred_devices; > > +static bool initcalls_done; > > Wait, why add this variable? No one uses it that I can see in this > patch, doesn't it create a build warning? > > You did test-build this, right? I just tested it, it causes a build warning, which implies that you did not test this :( greg k-h
On 07/08/2018 03:22 PM, Greg Kroah-Hartman wrote: > On Sun, Jul 08, 2018 at 03:21:07PM +0200, Greg Kroah-Hartman wrote: >> On Sun, Jul 08, 2018 at 02:32:56AM +0200, Javier Martinez Canillas wrote: >>> With Device Trees (DT), the dependencies of the devices are defined in the >>> DT, then the drivers parse that information to lookup the needed resources >>> that have as dependencies. >>> >>> Since drivers and devices are registered in a non-deterministic way, it is >>> possible that a device that is a dependency has not been registered yet by >>> the time that is looked up. >>> >>> In this case the driver that requires this dependency cannot probe and has >>> to defer it. So the driver core adds it to a list of deferred devices that >>> is iterated again every time that a new driver is probed successfully. >>> >>> For debugging purposes it may be useful to know what are the devices whose >>> probe function was deferred. Add a debugfs entry showing that information. >>> >>> $ cat /sys/kernel/debug/devices_deferred >>> 48070000.i2c:twl@48:bci >>> musb-hdrc.0.auto >>> omapdrm.0 >>> >>> This information could be obtained partially by enabling debugging, but it >>> means that the kernel log has to be parsed and the probe deferral balanced >>> with the successes. This can be error probe and has to be done in a ad-hoc >>> manner by everyone who needs to debug these kind of issues. >>> >>> Since the information is already known by the kernel, just show it to make >>> it easier to debug. >>> >>> Signed-off-by: Javier Martinez Canillas <javierm@redhat.com> >>> Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com> >>> Reviewed-by: Mark Brown <broonie@kernel.org> >>> >>> --- >>> >>> Changes since RFC v1: >>> - Remove unneeded ret variable from deferred_devs_show() >>> >>> Changes since RFC v2: >>> - Use DEFINE_SHOW_ATTRIBUTE() macro. >>> - Don't propagate debugfs_create_file() error. >>> - Remove IS_ENABLED(CONFIG_DEBUG_FS) guards. >>> - Drop RFC prefix. >>> >>> Changes since v1: >>> - Better explain in the commit message why this patch is useful. >>> - Rename deferred_devices entry to devices_deferred. >>> - Add an exit function and remove the debugfs entry. >>> >>> Changes since v2: >>> - Add Andy Shevchenko and Mark Brown Reviewed-by tag. >>> - Rebase on top of Greg's driver-core-next branch. >>> >>> >>> drivers/base/dd.c | 30 ++++++++++++++++++++++++++++++ >>> 1 file changed, 30 insertions(+) >>> >>> diff --git a/drivers/base/dd.c b/drivers/base/dd.c >>> index 6ea9c5cece7..140f534ee9c 100644 >>> --- a/drivers/base/dd.c >>> +++ b/drivers/base/dd.c >>> @@ -16,6 +16,7 @@ >>> * Copyright (c) 2007-2009 Novell Inc. >>> */ >>> >>> +#include <linux/debugfs.h> >>> #include <linux/device.h> >>> #include <linux/delay.h> >>> #include <linux/dma-mapping.h> >>> @@ -53,6 +54,8 @@ static DEFINE_MUTEX(deferred_probe_mutex); >>> static LIST_HEAD(deferred_probe_pending_list); >>> static LIST_HEAD(deferred_probe_active_list); >>> static atomic_t deferred_trigger_count = ATOMIC_INIT(0); >>> +static struct dentry *deferred_devices; >>> +static bool initcalls_done; >> >> Wait, why add this variable? No one uses it that I can see in this >> patch, doesn't it create a build warning? >> Argh, sorry about that. It was my bad when doing the conflict resolution. This variable got removed by commit 0a50f61c4fb ("drivers: base: initcall_debug logs for driver probe times") that made the patch to not apply cleanly anymore. >> You did test-build this, right? > > I just tested it, it causes a build warning, which implies that you did > not test this :( > I did but missed the build warning. > greg k-h > Best regards,
diff --git a/drivers/base/dd.c b/drivers/base/dd.c index 6ea9c5cece7..140f534ee9c 100644 --- a/drivers/base/dd.c +++ b/drivers/base/dd.c @@ -16,6 +16,7 @@ * Copyright (c) 2007-2009 Novell Inc. */ +#include <linux/debugfs.h> #include <linux/device.h> #include <linux/delay.h> #include <linux/dma-mapping.h> @@ -53,6 +54,8 @@ static DEFINE_MUTEX(deferred_probe_mutex); static LIST_HEAD(deferred_probe_pending_list); static LIST_HEAD(deferred_probe_active_list); static atomic_t deferred_trigger_count = ATOMIC_INIT(0); +static struct dentry *deferred_devices; +static bool initcalls_done; /* * In some cases, like suspend to RAM or hibernation, It might be reasonable @@ -199,6 +202,24 @@ void device_unblock_probing(void) driver_deferred_probe_trigger(); } +/* + * deferred_devs_show() - Show the devices in the deferred probe pending list. + */ +static int deferred_devs_show(struct seq_file *s, void *data) +{ + struct device_private *curr; + + mutex_lock(&deferred_probe_mutex); + + list_for_each_entry(curr, &deferred_probe_pending_list, deferred_probe) + seq_printf(s, "%s\n", dev_name(curr->device)); + + mutex_unlock(&deferred_probe_mutex); + + return 0; +} +DEFINE_SHOW_ATTRIBUTE(deferred_devs); + /** * deferred_probe_initcall() - Enable probing of deferred devices * @@ -208,6 +229,9 @@ void device_unblock_probing(void) */ static int deferred_probe_initcall(void) { + deferred_devices = debugfs_create_file("devices_deferred", 0444, NULL, + NULL, &deferred_devs_fops); + driver_deferred_probe_enable = true; driver_deferred_probe_trigger(); /* Sort as many dependencies as possible before exiting initcalls */ @@ -216,6 +240,12 @@ static int deferred_probe_initcall(void) } late_initcall(deferred_probe_initcall); +static void __exit deferred_probe_exit(void) +{ + debugfs_remove_recursive(deferred_devices); +} +__exitcall(deferred_probe_exit); + /** * device_is_bound() - Check if device is bound to a driver * @dev: device to check