Re: frequent lockups in 3.18rc4

[Dave Jones]

On Thu, Dec 04, 2014 at 10:51:03AM +0000, Will Deacon wrote:

 > and, as before, it has a weird child process that I can't backtrace:
 > 
 > trinity-c1      R  running task        0   861    811 0x00000000
 > Call trace:

When I get these, ftrace is a godsend.

cd /sys/kernel/debug/tracing/
echo 861 >> set_ftrace_pid
echo function_graph >> current_tracer
echo 1 >> tracing_on
wait a little while
cat trace > trace.txt

repeat last two steps if necessary

(assuming it's stuck in kernel space, which /proc/861/stack should
 be able to confirm. Usually when I see this problem, that just shows
 0xffffffffffffffff)

	Dave

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