On Thu, Mar 18, 2010 at 02:39:13PM +0800, Li Zefan wrote:
> David Miller wrote:
> > From: Frederic Weisbecker <fweisbec@xxxxxxxxx>
> > Date: Thu, 18 Mar 2010 05:49:33 +0100
> >
> >> While using the lock events through perf in a sparc box, I can see
> >> the following message repeated many times:
> >>
> >> Kernel unaligned access at TPC[49357c] perf_trace_lock_acquire+0xb4/0x180
> >>
> >> It actually hangs the box as the messages are sent to a serial console.
> >>
> >> When used with perf, the trace events use a per cpu buffer allocated
> >> in kernel/trace/trace_event_perf.c, and the allocation appears to return
> >> a misaligned percpu pointer. It is aligned to 4 while it seems it
> >> requires to be aligned to 8.
> >
> > Thanks I'll take a look at this.
> >
> > RAW locks (both rwlocks and spinlocks) on sparc64 are 4-bytes
> > in size, maybe some piece of code is assuming that locks
> > are cpu word sized.
> >
> > Where is perf_trace_lock_acquire() I can't find it in Linus's
> > tree? Does it get created by some crazy macro expansion?
> >
>
> Yes, it's expanded by some crazy macro in include/trace/ftrace.h..
>
> In linus' tree, it's called ftrace_profile_lock_acquire(), and it's
> renamed to perf_trace_lock_acquire() in -tip tree by commit
> 97d5a22005f38057b4bc0d95f81cd26510268794.
>
> #undef DECLARE_EVENT_CLASS
> #define DECLARE_EVENT_CLASS(call, proto, args, tstruct, assign, print) \
> static notrace void \
> ftrace_profile_templ_##call(struct ftrace_event_call *event_call, \
> proto) \
> { \
> struct ftrace_data_offsets_##call __maybe_unused __data_offsets;\
> struct ftrace_raw_##call *entry; \
> u64 __addr = 0, __count = 1; \
> unsigned long irq_flags; \
> int __entry_size; \
> int __data_size; \
> int rctx; \
> \
> ...
> }
Yeah indeed. The problem happens in Linus's tree and -tip tree as well,
it's just that I debugged it in -tip and there has been a naming change
inside, I forgot about that. So in mainline the problem happens in
ftrace_profile_templ_lock_acquire (macro generated above).
Thanks.
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