From: Frederic Weisbecker <fweisbec@gmail.com>
Date: Sun, 23 Nov 2008 05:22:56 +0000 (+0100)
Subject: tracing/function-return-tracer: store return stack into task_struct and allocate... 
X-Git-Tag: v2.6.29-rc1~586^2~49^4~3
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f201ae2356c74bcae130b2177b3dca903ea98071;p=pandora-kernel.git

tracing/function-return-tracer: store return stack into task_struct and allocate it dynamically

Impact: use deeper function tracing depth safely

Some tests showed that function return tracing needed a more deeper depth
of function calls. But it could be unsafe to store these return addresses
to the stack.

So these arrays will now be allocated dynamically into task_struct of current
only when the tracer is activated.

Typical scheme when tracer is activated:
- allocate a return stack for each task in global list.
- fork: allocate the return stack for the newly created task
- exit: free return stack of current
- idle init: same as fork

I chose a default depth of 50. I don't have overruns anymore.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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