Messages in this thread | | | Date | Fri, 19 Mar 2010 11:22:07 -0700 | From | Randy Dunlap <> | Subject | Re: 2.6.33 GP fault only when built with tracing |
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On 03/18/10 17:59, Mathieu Desnoyers wrote: > * Steven Rostedt (rostedt@goodmis.org) wrote: >> On Thu, 2010-03-18 at 16:26 -0700, Randy Dunlap wrote: >>> I can build/boot 2.6.33 with CONFIG_TRACE/TRACING disabled successfully, >>> but when I enable lots of tracing config options and then boot with >>> ftrace=nop on the kernel command line, I see a GP fault when the parport & >>> parport_pc modules are loading/initializing. >> >> Do you see it without adding the "ftrace=nop"? The only thing that >> should do is expand the ring buffer on boot up. >> >>> >>> It happens in drivers/parport/share.c::parport_register_device(), when that >>> function calls try_module_get(). >>> >>> If I comment out the trace_module_get() calls in include/linux/module.h, >>> the kernel boots with no problems. >> >> >> Interesting. Well, trace_module_get() is a TRACE_EVENT tracepoint. But >> should be disabled here. It may be something to do with DEFINE_TRACE. >> >> (added Mathieu to Cc since he wrote that code) > > can you try replacing the "local_read(__module_ref_addr(module, cpu))" argument > with "0" ?
Yes, that boots with no problems.
> Arguments with side-effects are not skipped by the jump over disabled > instrumentation. This is why we should do that part within the probe declaration > in the TRACE_EVENT macros. > > But if we find out that the problem really is this argument, then it should be > fixed, because something would be wrong with it (just moving it to TRACE_EVENT > is not a proper solution). > > Thanks, > > Mathieu
-- ~Randy
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