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authorSteven Rostedt <srostedt@redhat.com>2011-02-10 21:26:13 -0500
committerGreg Kroah-Hartman <gregkh@suse.de>2011-03-23 13:03:32 -0700
commit1883e22e58194ef67349ff23333defebaaafa530 (patch)
tree1e715bf19c93e1461f7d53787197377d4421c86a /arch
parent2c048b5dbd657781e9a37e8efa5c42d65c119057 (diff)
downloadlinux-2.6.38-lt-ux500-1883e22e58194ef67349ff23333defebaaafa530.tar.gz
ftrace: Fix memory leak with function graph and cpu hotplug
commit 868baf07b1a259f5f3803c1dc2777b6c358f83cf upstream. When the fuction graph tracer starts, it needs to make a special stack for each task to save the real return values of the tasks. All running tasks have this stack created, as well as any new tasks. On CPU hot plug, the new idle task will allocate a stack as well when init_idle() is called. The problem is that cpu hotplug does not create a new idle_task. Instead it uses the idle task that existed when the cpu went down. ftrace_graph_init_task() will add a new ret_stack to the task that is given to it. Because a clone will make the task have a stack of its parent it does not check if the task's ret_stack is already NULL or not. When the CPU hotplug code starts a CPU up again, it will allocate a new stack even though one already existed for it. The solution is to treat the idle_task specially. In fact, the function_graph code already does, just not at init_idle(). Instead of using the ftrace_graph_init_task() for the idle task, which that function expects the task to be a clone, have a separate ftrace_graph_init_idle_task(). Also, we will create a per_cpu ret_stack that is used by the idle task. When we call ftrace_graph_init_idle_task() it will check if the idle task's ret_stack is NULL, if it is, then it will assign it the per_cpu ret_stack. Reported-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Suggested-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'arch')
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