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From: Tim Kientzle <kientzle@freebsd.org>
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Subject: Every 20 minutes (less 4 seconds)?
Date: Tue, 1 Jan 2013 21:30:35 -0800
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I'm trying to understand why the transmitter for the
CPSW ethernet driver just stops sometimes.

I just found a very perplexing clue:  It happens
every 1196 seconds.

I added a debug message with an HH:MM:SS
timestamp whenever the watchdog sees the
transmitter stop and this is what it printed out:

20:30:20 cpsw_tx_watchdog Watchdog resetting driver
20:50:16 cpsw_tx_watchdog Watchdog resetting driver
21:10:12 cpsw_tx_watchdog Watchdog resetting driver
21:30:09 cpsw_tx_watchdog Watchdog resetting driver
21:50:04 cpsw_tx_watchdog Watchdog resetting driver
22:10:01 cpsw_tx_watchdog Watchdog resetting driver
22:29:56 cpsw_tx_watchdog Watchdog resetting driver
22:49:52 cpsw_tx_watchdog Watchdog resetting driver
23:09:49 cpsw_tx_watchdog Watchdog resetting driver
23:29:45 cpsw_tx_watchdog Watchdog resetting driver
23:49:41 cpsw_tx_watchdog Watchdog resetting driver
00:29:33 cpsw_tx_watchdog Watchdog resetting driver
00:49:29 cpsw_tx_watchdog Watchdog resetting driver
01:29:21 cpsw_tx_watchdog Watchdog resetting driver
02:29:09 cpsw_tx_watchdog Watchdog resetting driver
03:28:57 cpsw_tx_watchdog Watchdog resetting driver
04:28:45 cpsw_tx_watchdog Watchdog resetting driver
05:28:31 cpsw_tx_watchdog Watchdog resetting driver

(Note:  Some 20-minute intervals did seem to get skipped.
There was no hang at 01:09, 01:49, 02:09, 02:49, etc.
Maybe because the system was less busy then?  The
network and processor load varied quite a bit over
this 9 hour period.)

Based on this, it would appear that "something"
happens every 1196 seconds and if "something else"
happens at that time the transmitter will hang.

Does anyone recognize that particular period?

Tim

P.S. Cron isn't running, nor is there any other particularly
periodic process.