722b3c7469
Currently the index to the ret_stack is updated and the real return address is saved in the ret_stack. Then we call the trace function. The trace function could decide that it doesn't want to trace this function (ex. set_graph_function does not match) and it will return 0 which means not to trace this call. The normal function graph tracer has this code: if (!(trace->depth || ftrace_graph_addr(trace->func)) || ftrace_graph_ignore_irqs()) return 0; What this states is, if the trace depth (which is curr_ret_stack) is zero (top of nested functions) then test if we want to trace this function. If this function is not to be traced, then return 0 and the rest of the function graph tracer logic will not trace this function. The problem arises when an interrupt comes in after we updated the curr_ret_stack. The next function that gets called will have a trace->depth of 1. Which fools this trace code into thinking that we are in a nested function, and that we should trace. This causes interrupts to be traced when they should not be. The solution is to trace the function first and then update the ret_stack. Reported-by: zhiping zhong <xzhong86@163.com> Reported-by: wu zhangjin <wuzhangjin@gmail.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> |
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