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Date: Wed, 25 Feb 2015 11:53:16 +0900 From: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com> To: Arnaldo Carvalho de Melo <acme@...nel.org> Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Jiri Olsa <jolsa@...hat.com>, David Ahern <dsahern@...il.com> Subject: Re: Trying to use 'perf probe' to debug perf itself Hi Arnaldo, (2015/02/25 3:49), Arnaldo Carvalho de Melo wrote: > Hi Masami, > > I'm adding thread refcounting in perf, and in this process I am > investigating a problem, so thought about using perf itself to match > thread__get with thread__put: > > [root@...andy ~]# perf probe -x ~/bin/perf -V thread__put > Available variables at thread__put > @<thread__put+0> > struct thread* thread > [root@...andy ~]# perf probe -x ~/bin/perf -V thread__get > Available variables at thread__get > @<thread__get+0> > struct thread* thread > [root@...andy ~]# > > cool, so I thought it would be just a matter of asking to put the probes > and get the value of 'thread', then match things, but: > > > [root@...andy ~]# perf probe -v ~/bin/perf thread__put thread > probe-definition(0): thread__put thread > symbol:thread__put file:(null) line:0 offset:0 return:0 lazy:(null) > parsing arg: thread into thread > 1 arguments > Open Debuginfo file: /root/bin/perf > Try to find probe point from debuginfo. > Probe point found: thread__put+0 > Searching 'thread' variable in context. > Converting variable thread into trace event. > thread type is (null). > Found 1 probe_trace_events. > Opening /sys/kernel/debug/tracing/uprobe_events write=1 > Added new event: > Writing event: p:probe_perf/thread__put /root/bin/perf:0xd03d2 thread=-32(%sp):u64 > Failed to write event: Invalid argument > Error: Failed to add events. Reason: Invalid argument (Code: -22) > [root@...andy ~]# > > Not possible :-\ Hmm, strange. Could you tell me the version of your kernel? It seems that the kernel newer than 3.14 supports uprobes with memory dereference (e.g. -32(%sp) )feature. (it was actually introduced by 5baaa59e, and git-describe told it was v3.13-rc4-22-g5baaa59) And also, could you try to write the result command to uprobe_event as below? # echo "p:probe_perf/thread__put /root/bin/perf:0xd03d2 thread=-32(%sp):u64" >> \ /sys/kernel/debug/tracing/uprobe_events > > please let me know if you need some file, here is the readelf -wi for > those two routines: This should not be the problem of dwarf-analysis. It seems kernel-side (uprobe) problem. Thank you, > > # readelf -wi ~/bin/perf > <SNIP> > <1><e25f1>: Abbrev Number: 35 (DW_TAG_subprogram) > <e25f2> DW_AT_external : 1 > <e25f2> DW_AT_name : (indirect string, offset: 0x4c5c3): thread__get > <e25f6> DW_AT_decl_file : 6 > <e25f7> DW_AT_decl_line : 84 > <e25f8> DW_AT_prototyped : 1 > <e25f8> DW_AT_type : <0xe15cc> > <e25fc> DW_AT_low_pc : 0x4d038c > <e2604> DW_AT_high_pc : 0x46 > <e260c> DW_AT_frame_base : 1 byte block: 9c (DW_OP_call_frame_cfa) > <e260e> DW_AT_GNU_all_tail_call_sites: 1 > <e260e> DW_AT_sibling : <0xe2621> > <2><e2612>: Abbrev Number: 32 (DW_TAG_formal_parameter) > <e2613> DW_AT_name : (indirect string, offset: 0x43dc7): thread > <e2617> DW_AT_decl_file : 6 > <e2618> DW_AT_decl_line : 84 > <e2619> DW_AT_type : <0xe15cc> > <e261d> DW_AT_location : 2 byte block: 91 58 (DW_OP_fbreg: -40) > <2><e2620>: Abbrev Number: 0 > <1><e2621>: Abbrev Number: 39 (DW_TAG_subprogram) > <e2622> DW_AT_external : 1 > <e2622> DW_AT_name : (indirect string, offset: 0x4c699): thread__put > <e2626> DW_AT_decl_file : 6 > <e2627> DW_AT_decl_line : 90 > <e2628> DW_AT_prototyped : 1 > <e2628> DW_AT_low_pc : 0x4d03d2 > <e2630> DW_AT_high_pc : 0x6c > <e2638> DW_AT_frame_base : 1 byte block: 9c (DW_OP_call_frame_cfa) > <e263a> DW_AT_GNU_all_tail_call_sites: 1 > <e263a> DW_AT_sibling : <0xe264d> > <2><e263e>: Abbrev Number: 32 (DW_TAG_formal_parameter) > <e263f> DW_AT_name : (indirect string, offset: 0x43dc7): thread > <e2643> DW_AT_decl_file : 6 > <e2644> DW_AT_decl_line : 90 > <e2645> DW_AT_type : <0xe15cc> > <SNIP> > > Will see what I can do with just: > > [root@...andy ~]# perf probe ~/bin/perf thread__get > Added new event: > probe_perf:thread__get (on thread__get in /root/bin/perf) > > You can now use it in all perf tools, such as: > > perf record -e probe_perf:thread__get -aR sleep 1 > > [root@...andy ~]# perf probe ~/bin/perf thread__put > Added new event: > probe_perf:thread__put (on thread__put in /root/bin/perf) > > You can now use it in all perf tools, such as: > > perf record -e probe_perf:thread__put -aR sleep 1 > > [root@...andy ~]# perf list probe*:* > > List of pre-defined events (to be used in -e): > > probe_perf:thread__put [Tracepoint event] > probe_perf:thread__get [Tracepoint event] > [root@...andy ~]# perf probe -l > probe_perf:thread__get (on thread__get@...l/thread.c in /root/bin/perf) > probe_perf:thread__put (on thread__put@...l/thread.c in /root/bin/perf) > [root@...andy ~]# > > - Arnaldo > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@...r.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- Masami HIRAMATSU Software Platform Research Dept. Linux Technology Research Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@...achi.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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