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SubjectRe: [PATCH] power: supply: sysfs: prevent endless uevent loop with CONFIG_POWER_SUPPLY_DEBUG
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"):
>
> 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
>
> Both CONFIG_I2C_DEBUG_CORE and CONFIG_POWER_SUPPLY_DEBUG were reported
> in https://bugs.freedesktop.org/show_bug.cgi?id=76886 but only former
> seems to have been fixed. Change debug prints to use pr_debug insted
> to resolve the issue.
>
> 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(-)
>
> diff --git a/drivers/power/supply/power_supply_sysfs.c b/drivers/power/supply/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;
>
> - dev_dbg(dev, "uevent\n");
> + pr_debug("%s: uevent\n", dev_name(dev));
>
> if (!psy || !psy->desc) {
> dev_dbg(dev, "No power supply yet\n");
> return ret;
> }
>
> - dev_dbg(dev, "POWER_SUPPLY_NAME=%s\n", psy->desc->name);
> + pr_debug("%s: POWER_SUPPLY_NAME=%s\n", dev_name(dev), psy->desc->name);
>
> ret = add_uevent_var(env, "POWER_SUPPLY_NAME=%s", psy->desc->name);
> if (ret)
> @@ -427,7 +427,8 @@ int power_supply_uevent(struct device *dev, struct kobj_uevent_env *env)
> goto out;
> }
>
> - dev_dbg(dev, "prop %s=%s\n", attrname, prop_buf);
> + pr_debug("%s: prop %s=%s\n", dev_name(dev), attrname,
> + prop_buf);
>
> ret = add_uevent_var(env, "POWER_SUPPLY_%s=%s", attrname, prop_buf);
> kfree(attrname);
> --
> 2.20.1
>
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