On Sun, 5 Aug 2018 09:46:56 -0700 Joel Fernandes <[email protected]> wrote:
> Hi Masami, > > On Fri, Aug 3, 2018 at 9:51 PM, Joel Fernandes <[email protected]> wrote: > [...] > >> On Thu, 2 Aug 2018 19:57:09 -0700 > >> Joel Fernandes <[email protected]> wrote: > >> > >>> Hi Masami, > >>> > >>> On Thu, Aug 2, 2018 at 7:55 AM, Masami Hiramatsu <[email protected]> > >>> wrote: > >>> > Hi Joel, > >>> > > >>> > I found this caused several issues when testing ftrace. > >>> > > >>> > #1) ftrace boottest (FTRACE_STARTUP_TEST) fails > >>> > >>> This sadly appears to be a real issue. The startup test for > >>> "preemptirqsoff" tracer fails, however it passes for only preemptoff > >>> or only irqsoff. I tested only the last 2 tracers, not the first one, > >>> that's why I didn't catch it. I need to debug this more. > > I figured out this one too. Its because I need to account for > preempt_count() in tracer_hardirqs_off since the tracer probe is now > called with an additional level of preempt disabled from the > tracepoint code. Without that accounting, stop_critical_timings may > not be called causing an empty trace buffer. That should be easy to > fix, I'm on vacation though and back on 13th so can most likely look > at it only then (the week after the next). Nice! Thank you for identifying the root cause! BTW, I'm also on vacation this week :) > >>> > #2) mmiotrace reports "IRQs not enabled as expected" error > >>> > #3) lock subsystem event boottest causes "IRQs not disabled as > >>> > expected" error (sometimes) > > The only thing left to figure out is #3 ("lock subsystem event > boottest"). Could you let me know how to run this test? The #3 is not always reproducible, I just enabled these 2 configs CONFIG_FTRACE_STARTUP_TEST=y and CONFIG_EVENT_TRACE_TEST_SYSCALLS=y and boot on Qemu. I have seen this issue about 10% of system boot. Thank you, -- Masami Hiramatsu <[email protected]>
