Hi Sebastian,
> > The code that is causing the long latencies seems to be the function
> > "igb_watchdog_task" within igb_main.c (Line: 4386).
> > This function will be called periodically.
> > When I do a return at the beginning of this function the additional latency is not
> seen.
> > In particular that function calls "igb_has_link" which seems to be one
> > candidate that is causing additional latency.
> > Do you have any clue how this code can be executed properly without
> > causing the additional latencies?
>
> Nope. The watchdog function is invoked via schedule_work() so it should not be
> blocking anything. There is no preempt disable or anything like that. Could you
> narrow it down further? The igb_has_link() seems also small and simple.
>
OK. I tried to dig deeper into that....
The critical stuff seems to be
igb_has_link() calling hw->mac_ops.check_for_link (which is igb_check_for_link_82575() )
calling igb_check_for_copper_link() calling igb_phy_has_link.
Within igb_phy_has_link() the line with the code
ret_val = hw->phy.ops.read_reg(hw, PHY_STATUS, &phy_status);
seems to be the candidate that causing the trouble.
And this function pointer points to igb_read_phy_reg_82580().
Does this give you any idea what goes wrong?
Thanks for any hints!
Regards
Mathias
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