Messages in this thread | | | Date | Tue, 18 Nov 2008 23:17:21 +0800 | From | walimis <> | Subject | Re: [PATCH 1/1] ftrace: fix wrong pos computing when read buffer has been fulfilled. |
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On Tue, Nov 18, 2008 at 09:36:07AM -0500, Steven Rostedt wrote: > >On Sat, 15 Nov 2008, walimis wrote: > >> >> hi Steven, >> >> Could you help me to review this patch? >> >> Thanks. >> >> Impact: make output of available_filter_functions complete >> >> phenomenon: >> >> The first value of dyn_ftrace_total_info is not equal with >> `cat available_filter_functions | wc -l`, but they should be equal. >> >> root cause: >> >> When printing functions with seq_printf in t_show, if the read buffer >> is just overflowed by current function record, then this function >> won't be printed to user space through read buffer, it will >> just be dropped. So we can't see this function printing. >> So, every time the last function to fill the read buffer, if overflowed, >> will be dropped. >> This also applies to set_ftrace_filter if set_ftrace_filter has >> more bytes than read buffer. >> >> fix: >> >> Through checking return value of seq_printf, if less than 0, we know >> this function doesn't be printed. Then we decrease position to force >> this function to be printed next time, in next read buffer. > >A lot of the code for seq files I cut and paste from other places that I >have written it. The seq files always confuse me, so I like to use stuff >that worked before. Some of the things that walimis fixed were not needed >for this file, and was overkill. It also confuse me a lot. I also checked all places using seq files in trace/ftrace code, to see whether there are similar problem. - trace.c: in s_start() it force pos to decrease one such as: l = *pos - 1; so it works well. - trace_stack.c: t_start, in almost all cases, can be only called once, so we don't see the error. But I wonder whether it still works well if output message exceeds the size of seq file buffer and call t_start twice. If needed, I can test it. - trace_branch.c : the same with above.
walimis > >> >> another little fix is to show correct allocating pages count. > >Ack. > >> >> Signed-off-by: walimis <walimisdev@gmail.com> > >Acked-by: Steven Rostedt <srostedt@redhat.com> > >-- Steve
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