On Wed, Mar 23, 2016 at 05:50:33PM +0100, Wolfram Sang wrote:
> On Wed, Mar 23, 2016 at 04:50:47PM +0100, Jan Glauber wrote:
> > After enabling CONFIG_I2C_DEBUG_CORE my system was broken
> > (no network, console login not possible). System log was
> > flooded with the this message:
> >
> > ...
> > [ 608.052077] rtc-ds1307 0-0068: uevent
> > [ 608.052500] rtc-ds1307 0-0068: uevent
> > [ 608.052925] rtc-ds1307 0-0068: uevent
> > ...
> >
> > The culprit is the dev_dbg printk in the i2c uevent handler.
> > If this is activated (for instance by CONFIG_I2C_DEBUG_CORE)
> > it results in an endless loop with systemd-journald.
> >
> > This happens if user-space scans the system log and reads the uevent
> > file to get information about a newly created device, which seems fair
> > use to me. Unfortunately reading the "uevent" file uses the same
> > function that runs for creating the uevent for a new device,
> > generating the next syslog entry.
> >
> > Ideally user-space would implement a recursion detection and
> > after reading the same device file for the 1000th time call it a
> > day, but nevertheless I think we should avoid this problem by
> > removing the debug print completly or using another print variant.
>
> Thanks for pointing out this problem. I think this debug can go. I also
> think the function can be cleaned up some more. Can you test this patch?
Works for me!
Thanks, Jan
> Thanks,
>
> Wolfram
>
> diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
> index 0f2f8484e8ec1f..e584d88ee337f6 100644
> --- a/drivers/i2c/i2c-core.c
> +++ b/drivers/i2c/i2c-core.c
> @@ -525,22 +525,16 @@ static int i2c_device_match(struct device *dev, struct device_driver *drv)
> return 0;
> }
>
> -
> -/* uevent helps with hotplug: modprobe -q $(MODALIAS) */
> static int i2c_device_uevent(struct device *dev, struct kobj_uevent_env *env)
> {
> - struct i2c_client *client = to_i2c_client(dev);
> + struct i2c_client *client = to_i2c_client(dev);
> int rc;
>
> rc = acpi_device_uevent_modalias(dev, env);
> if (rc != -ENODEV)
> return rc;
>
> - if (add_uevent_var(env, "MODALIAS=%s%s",
> - I2C_MODULE_PREFIX, client->name))
> - return -ENOMEM;
> - dev_dbg(dev, "uevent\n");
> - return 0;
> + return add_uevent_var(env, "MODALIAS=%s%s", I2C_MODULE_PREFIX, client->name);
> }
>
> /* i2c bus recovery routines */
>
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