Messages in this thread | | | Date | Wed, 3 Jun 2009 09:23:11 -0400 (EDT) | From | Steven Rostedt <> | Subject | Re: trace: fix multiple use of __print_flags and __print_symbolic |
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On Wed, 3 Jun 2009, Steven Whitehouse wrote:
> Hi > > On Wed, 2009-06-03 at 17:50 +0800, Li Zefan wrote: > > Steven Whitehouse wrote: > > > When using multiple calls to __print_symbolic and __print_flags in > > > the same tracer, I noticed that the output was incorrect. I think > > > the following patch is the correct fix (it works for me) but please > > > check it carefully since I'm not that familiar with this code, > > > and I may well have made a mistake somewhere. > > > > > > > I don't see there's bug in __print_symbolic() or __print_flags(): > > > > enum print_line_t > > ftrace_raw_output_##call(struct trace_iterator *iter, int flags) > > { > > ... > > p = &get_cpu_var(ftrace_event_seq); > > /* here we call ftrace_print_flags_seq(p, ...) */ > > ret = trace_seq_printf(s, #call ": " print); > > put_cpu(); > > ... > > } > > > > ftrace_event_seq is percpu data, and here is used with preempt-disabled, > > so there shouldn't be problem of concurrent accessing. > > > I've double checked this now, and I'm seeing results like: > > > glock_workqueue-2482 [001] 809.956985: gfs2_glock_state_change: 8.7 glock 2:33119 state EX => EX tgt:EX dmt:EX flags:EX > glock_workqueue-2482 [001] 809.957155: gfs2_glock_state_change: 8.7 glock 2:33119 state NL => NL tgt:NL dmt:NL flags:NL > glock_workqueue-2482 [001] 809.959473: gfs2_glock_state_change: 8.7 glock 1:2 state NL => NL tgt:NL dmt:NL flags:NL > glock_workqueue-2482 [001] 809.959556: gfs2_glock_state_change: 8.7 glock 2:33119 state EX => EX tgt:EX dmt:EX flags:EX > glock_workqueue-2482 [001] 810.008773: gfs2_glock_state_change: 8.7 glock 1:0 state EX => EX tgt:EX dmt:EX flags:EX > > > without the patch, which is clearly wrong,
Ah, I did not account for having multiple instances of print_symbol of print_flags in a single print. Your patch is partialy correct. Add a:
trace_seq_init(p);
after the "p = &get_cpu_var(ftrace_event_seq);".
-- Steve
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