2008/12/13 Vladislav Bolkhovitin <vst@xxxxxxxx>: > Also (maybe I simply miss something) looks like ftrace doesn't trace exit > from functions, only entrance to them. Is it true? Is it possibly to log > exit from functions as well? That's true with 2.6.28, the function tracer traces on function entries only. But there is an add-on on ftrace which let one to trace on entry and on return, the function graph tracer. This tracer uses this facility to output a graph of function calls and measure the time elapsed during each function call. You can also register two custom handlers to do some things you need on entry and on return. > All the above functionality is almost what we need. The only thing left, > which I forgot to mention, is possibility to log also functions return value > on exit. This is what TRACE_EXIT_RES() in SCST does. Is it possible to add > those? I want to add that on the function graph tracer. That can be done pretty easily. The only problem comes with the type of the return value. Would this tracer be supposed to always return a 64 bits value regardless of the real typ of the value? There would be some pointless bytes on most return values. I don't know how to proceed for this problem. > And one more question. Is it possible to redirect ftrace tracing to serial > console or any other console (netconsole?)? It can be helpful to investigate > hard lockups in IRQ or with IRQs disabled. > > Thanks! > Vlad > I would find it useful too. I thought about something like using early_printk or something like that...I don't know. That would be good to redirect the output to the tty device of the user choice. -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
