Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1367164

Re: [PATCH] i2c: prevent endless uevent loop with CONFIG_I2C_DEBUG_CORE

Show all headers | View raw

[Multipart message — attachments visible in raw view] - view raw

On Wed, Mar 23, 2016 at 08:47:02PM +0100, Wolfram Sang wrote:
> Jan reported this:
> ===
> 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.
> 
> The same problem seems to be reported here:
> https://bugs.freedesktop.org/show_bug.cgi?id=76886
> ===
> 
> His patch converted the message to pr_debug, but I think the debug can
> simply go. We have other means to see code paths these days. This
> enables us to clean up the function some more while we are here.
> 
> Reported-by: Jan Glauber <jglauber@cavium.com>
> Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
> Acked-by: Alexander Sverdlin <alexander.sverdlin@nokia.com>
> Tested-by: Jan Glauber <jglauber@cavium.com>

Applied to for-current, thanks!

Back to linux.kernel | Previous | Next — Previous in thread | Find similar | Unroll thread

Thread

[PATCH] i2c: prevent endless uevent loop with CONFIG_I2C_DEBUG_CORE Wolfram Sang <wsa@the-dreams.de> - 2016-03-23 20:50 +0100
  Re: [PATCH] i2c: prevent endless uevent loop with  CONFIG_I2C_DEBUG_CORE Wolfram Sang <wsa@the-dreams.de> - 2016-03-30 14:30 +0200

csiph-web