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powerpc/ftrace: Trace function graph entry before updating index 

As Colin Cross ported my x86 change to ARM, he also pointed out that
powerpc is also behind in this fix.

The commit 722b3c7469 "ftrace/graph: Trace function entry before
updating index" fixes an issue with function graph tracing for x86,
where if the called entry function decides not to trace interrupts, it
can fail the check if an interrupt comes in just after the
curr_ret_stack is updated.

The solution is to call the entry function first, then update the
curr_ret_stack if the entry function wants to be traced.

Cc: Colin Cross <ccross@android.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Steven Rostedt 2012-07-18 12:35:28 +00:00 committed by Benjamin Herrenschmidt
parent e5ae3cdfd5
commit bac821a6e3
1 changed files with 6 additions and 7 deletions
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13
arch/powerpc/kernel/ftrace.c
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@ -630,18 +630,17 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
return;
}
if (ftrace_push_return_trace(old, self_addr, &trace.depth, 0) == -EBUSY) {
trace.func = self_addr;
trace.depth = current->curr_ret_stack + 1;
/* Only trace if the calling function expects to */
if (!ftrace_graph_entry(&trace)) {
*parent = old;
return;
}
trace.func = self_addr;
/* Only trace if the calling function expects to */
if (!ftrace_graph_entry(&trace)) {
current->curr_ret_stack--;
if (ftrace_push_return_trace(old, self_addr, &trace.depth, 0) == -EBUSY)
*parent = old;
}
}
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */