From 8dcf32175b4e1817ea037a051f10dd7823e52344 Mon Sep 17 00:00:00 2001 From: Wolfram Sang Date: Wed, 23 Mar 2016 20:47:02 +0100 Subject: [PATCH] i2c: prevent endless uevent loop with CONFIG_I2C_DEBUG_CORE 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 completely 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 Signed-off-by: Wolfram Sang Acked-by: Alexander Sverdlin Tested-by: Jan Glauber --- drivers/i2c/i2c-core.c | 10 ++-------- 1 file changed, 2 insertions(+), 8 deletions(-) diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c index 0f2f8484e8ec..e584d88ee337 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 */ -- 2.20.1