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Date:   Thu, 18 Apr 2019 00:37:08 +0200
From:   Sebastian Reichel <sre@kernel.org>
To:     Andrey Smirnov <andrew.smirnov@gmail.com>
Cc:     Chris Healy <cphealy@gmail.com>, linux-pm@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] power: supply: sysfs: prevent endless uevent loop with
 CONFIG_POWER_SUPPLY_DEBUG
Message-ID: <20190417223708.4irrwrm4q7vig3vh@earth.universe>
References: <20190405073020.10361-1-andrew.smirnov@gmail.com>
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Hi,

On Fri, Apr 05, 2019 at 12:30:20AM -0700, Andrey Smirnov wrote:
> Fix a similar endless event loop as was done in commit 8dcf32175b4e
> ("i2c: prevent endless uevent loop with CONFIG_I2C_DEBUG_CORE"):
>=20
>   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.
>=20
>   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
>=20
> Both CONFIG_I2C_DEBUG_CORE and CONFIG_POWER_SUPPLY_DEBUG were reported
> in https://bugs.freedesktop.org/show_bug.cgi?id=3D76886 but only former
> seems to have been fixed. Change debug prints to use pr_debug insted
> to resolve the issue.
>=20
> Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
> Cc: Chris Healy <cphealy@gmail.com>
> Cc: Sebastian Reichel <sre@kernel.org>
> Cc: linux-pm@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> ---

I think we should just drop these debug messages, just like I2C did.
They don't offer any useful information considering the info is already
exposed to userspace via the uevent.

-- Sebastian

>  drivers/power/supply/power_supply_sysfs.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
>=20
> diff --git a/drivers/power/supply/power_supply_sysfs.c b/drivers/power/su=
pply/power_supply_sysfs.c
> index dce24f596160..5e91946731fd 100644
> --- a/drivers/power/supply/power_supply_sysfs.c
> +++ b/drivers/power/supply/power_supply_sysfs.c
> @@ -383,14 +383,14 @@ int power_supply_uevent(struct device *dev, struct =
kobj_uevent_env *env)
>  	char *prop_buf;
>  	char *attrname;
> =20
> -	dev_dbg(dev, "uevent\n");
> +	pr_debug("%s: uevent\n", dev_name(dev));
> =20
>  	if (!psy || !psy->desc) {
>  		dev_dbg(dev, "No power supply yet\n");
>  		return ret;
>  	}
> =20
> -	dev_dbg(dev, "POWER_SUPPLY_NAME=3D%s\n", psy->desc->name);
> +	pr_debug("%s: POWER_SUPPLY_NAME=3D%s\n", dev_name(dev), psy->desc->name=
);
> =20
>  	ret =3D add_uevent_var(env, "POWER_SUPPLY_NAME=3D%s", psy->desc->name);
>  	if (ret)
> @@ -427,7 +427,8 @@ int power_supply_uevent(struct device *dev, struct ko=
bj_uevent_env *env)
>  			goto out;
>  		}
> =20
> -		dev_dbg(dev, "prop %s=3D%s\n", attrname, prop_buf);
> +		pr_debug("%s: prop %s=3D%s\n", dev_name(dev), attrname,
> +			 prop_buf);
> =20
>  		ret =3D add_uevent_var(env, "POWER_SUPPLY_%s=3D%s", attrname, prop_buf=
);
>  		kfree(attrname);
> --=20
> 2.20.1
>=20

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