@@ -125,23 +125,20 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
* on other archs. It's unlikely on AArch64.
*/
old = *parent;
- *parent = return_hooker;
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;
+ if (!ftrace_graph_entry(&trace))
return;
- }
err = ftrace_push_return_trace(old, self_addr, &trace.depth,
frame_pointer);
- if (err == -EBUSY) {
- *parent = old;
+ if (err == -EBUSY)
return;
- }
+ else
+ *parent = return_hooker;
}
#ifdef CONFIG_DYNAMIC_FTRACE
Function graph tracer modifies a return address (LR) in a stack frame by calling ftrace_prepare_return() in a traced function's function prologue. The current code does this modification before preserving an original address at ftrace_push_return_trace() and there is always a small window of inconsistency when an interrupt occurs. This doesn't matter, as far as an interrupt stack is introduced, because stack tracer won't be invoked in an interrupt context. But it would be better to proactively minimize such a window by moving the LR modification after ftrace_push_return_trace(). Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org> --- arch/arm64/kernel/ftrace.c | 11 ++++------- 1 file changed, 4 insertions(+), 7 deletions(-) -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/