From mboxrd@z Thu Jan  1 00:00:00 1970
From: Matthias Meier <matthias.j.meier@gmx.net>
Subject: Long max latencies on Wandbaord / Freescale i.MX6
Date: Fri, 2 Oct 2015 08:48:00 +0200
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Comming to the end of my CONFIG_PROVE_LOCKING / "max latency" story:

It is not a spurious interrupt...

The source of problem is the WiFi driver (brcmfmac via SDIO) which 
produces up to 6k interrupts per second, which when 
CONFIG_PROOVE_LOCKING is enabled, results sporadically in very long 
latencies (up to 10ms). (Possible because pending interrupts were queued).

Further after exactly 1600001 interrupts, the kernel disables this mmc 
interrupt with "__report_bad_irq"
(The mmc driver is not only used for SD-cards but also for the SDIO 
attached devices.)

Or with other words: never use (this) WiFi on a realtime system...

Regards and sorry for the noise I produced on this list
	Matthias