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C3/B3/C2-Series with "Excessive Interrupts Received for I2C interface" messages


Userlevel 3
Article ID: 13714

Products
C3-Series, firmware 6.42.02.0006 and higher
B3-Series, firmware 6.42.02.0006 and higher
C2-Series, firmware 5.02.12.0006 and higher

Symptoms
Possible high CPU utilization ('show system utilization cpu') in the "CPLD_Status" task.

"Interrupt/polling" messages seen in the logging buffer ('show logging buffer') and current.log (5487); for example:<160>Jan 3 11:36:02 0.0.0.0-2 SIM[108071544]: hwutils.c(3364) 301 %%
Excessive Interrupts Received for I2C interface for unit 2.
<160>Jan 3 11:36:02 0.0.0.0-2 SIM[108071544]: hwutils.c(3365) 302 %%
Switching to software polling.
<160>Jan 3 11:36:02 0.0.0.0-2 SIM[108071544]: hwutils.c(3366) 303 %%
Excessive Interrupts Received for I2C interface for unit 2.
<160>Jan 3 11:36:02 0.0.0.0-2 SIM[108071544]: hwutils.c(3367) 304 %%
Switching to software polling.[/code]The message may alternately include a reference to the specific interrupt:<160>Dec 4 00:26:35 0.0.0.0-2 SIM[216517472]: hwutils.c(4397) 40 %%
Excessive Interrupts Received for Internal PS for unit 2.
<160>Dec 4 00:26:35 0.0.0.0-2 SIM[216517472]: hwutils.c(4398) 41 %%
Switching to software polling.
<160>Jan 19 10:14:16 0.0.0.0-3 SIM[103760840]: hwutils.c(4311) 73 %%
Excessive Interrupts Received for Fan 2 for unit 3.
<160>Jan 19 10:14:16 0.0.0.0-3 SIM[103760840]: hwutils.c(4312) 74 %%
Switching to software polling.[/code]Cause
These messages can occur during run time as the system is monitoring various interrupts. Here the system has changed the interrupting device from an interrupt mode to a polling mode (periodic sampling), to prevent excessive CPU usage due to servicing low priority interrupts. These interrupts are not driven by traffic but by external devices like fans, PHYs, and power supplies. Once the messages are seen then you should not see them anymore unless a manual reset takes place and the system returns to interrupt mode.

Solution
Functions as Designed (FAD).

The system will switch back to interrupt mode following a unit reset. There is no reason to reset the unit, as everything will run as normal. It will not cause any issues.

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