RT throttling and mmc hardware interrupt timeout

[Jamie Huang <jamienstar@163.com>]

Hi all:
	Recently, I do test with btrfs filesystem on emmc. When I see
	the message "sched: RT throttling activated", uart, network and
	other peripherals are not responding.
	But, the timer is ok, so I can see the following messages:
	"mmc0: Timeout waiting for hardware interrupt." again and again.
	Finally, "I/O error" messages are coming and the btrfs
	filesystem crashes.

	I think, because I use threadirqs, so most irqs are processed
	in threads, yes, RT threads. When "sched: RT throttling
	activated" comes out, RT threads can not be execute for some
	time, so, we can see mmc interrupt timeout message.

	My kernel version is 3.10.55, I know that's very old. Still,
	I want to know, is there any patch for this problem? Or does
	any one encounter the same problem?  Thank you.