On Wed, 16 Nov 2011, Steven Rostedt wrote:

On Wed, 2011-11-16 at 17:42 +0800, Yong Zhang wrote:

quoted

Otherwise we will get below warning:

BUG: sleeping function called from invalid context at /build/linux/kernel/rtmutex.c:645
in_atomic(): 1, irqs_disabled(): 1, pid: 1054, name: migration/9
no locks held by migration/9/1054.
irq event stamp: 36
hardirqs last  enabled at (35): [<ffffffff815f5b50>] _raw_spin_unlock_irq+0x30/0x70
hardirqs last disabled at (36): [<ffffffff810b7eaf>] stop_machine_cpu_stop+0x8f/0x110
softirqs last  enabled at (0): [<ffffffff81051b53>] copy_process+0x6d3/0x1640
softirqs last disabled at (0): [<          (null)>]           (null)
Pid: 1054, comm: migration/9 Not tainted 3.2.0-rc1-rt2-11312-gbf51260-dirty #12
Call Trace:

Thomas, doesn't printk not print to serial in atomic contexts? Or did
that change?

Not that I know of.