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List:       opensolaris-dtrace-discuss
Subject:    Re: [dtrace-discuss] output of ustack only shows the library call
From:       Rayson Ho <rayrayson () gmail ! com>
Date:       2009-05-04 3:55:34
Message-ID: a0ba9d430905032055t3d698c66w1aaeaada952a35e () mail ! gmail ! com
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MySQL is a multi-threaded process, so what you are seeing is normal.

When DTrace is looking at the stack of a slave thread, it won't be
able to show you the call frame of main() because each thread has its
own stack.

BTW, what are you trying to trace?? There are already a number of
probes in MySQL.

Rayson



On 5/3/09, Qihua Wu <dtrace.wu@gmail.com> wrote:
> Thanks lejun.
>
> For the following output, the first called function (the last function show
> in ustack) is still not from a process (in this case mysqld).
>
> dtrace -n 'syscall::portfs:entry {ustack();}'
>
>  11  60041                     portfs:entry
>               libc.so.1`_portfs+0xa
>
> mysqld`_Z25ep_start_waiting_for_dataP12EP_FILE_INFO+0x55
>               mysqld`ep_thread_proc+0x194            ====>
> function of mysqld is in the middle of th ustack
>               libc.so.1`_thr_setup+0x5b
>               libc.so.1`_lwp_start
>     ===> this library call is the first call, but who called this function,
> should a call always started from function main()?
>
>  11  60041                     portfs:entry
>               libc.so.1`_portfs+0xa
>               mysqld`ep_thread_proc+0x81
>               libc.so.1`_thr_setup+0x5b
>               libc.so.1`_lwp_start
>
>  11  60041                     portfs:entry
>               libc.so.1`_portfs+0xa
>
> mysqld`_Z25ep_start_waiting_for_dataP12EP_FILE_INFO+0x55
>               mysqld`ep_thread_proc+0x194
>               libc.so.1`_thr_setup+0x5b
>               libc.so.1`_lwp_start
>
>  11  60041                     portfs:entry
>               libc.so.1`_portfs+0xa
>               mysqld`ep_thread_proc+0x81
>               libc.so.1`_thr_setup+0x5b
>               libc.so.1`_lwp_start
>
>  11  60041                     portfs:entry
>               libc.so.1`_portfs+0xa
>
> mysqld`_Z25ep_start_waiting_for_dataP12EP_FILE_INFO+0x55
>               mysqld`ep_thread_proc+0x194
>               libc.so.1`_thr_setup+0x5b
>               libc.so.1`_lwp_start
>
>
>
> 2009/5/4 Zhu, Lejun <lejun.zhu@intel.com>
>
> >
> >
> > Try increase "ustackframes", I think the default is 20 and you won't see
> the real entry point when ustack is too deep.
> >
> > ________________________________
> From: dtrace-discuss-bounces@opensolaris.org
> [mailto:dtrace-discuss-bounces@opensolaris.org] On Behalf
> Of Qihua Wu
> > Sent: 2009Äê5Ô 4ÈÕ 9:59
> > To: dtrace-discuss@opensolaris.org
> > Subject: [dtrace-discuss] output of ustack only shows the library call but
> no program call which called the library
> >
> >
> >
> >
> >
> > After I run dtrace -n 'syscall::brk:entry {ustack()}', I found some output
> show the function from ONLY library. But libaray is not runnable by itself.
> >
> >
> > 0  59753                        brk:entry
> >               libc.so.1`_brk_unlocked+0xa
> >               libc.so.1`sbrk+0x20
> >               libc.so.1`_morecore+0x12b
> >               libc.so.1`_malloc_unlocked+0x10d
> >               libc.so.1`malloc+0x2d
> >               libproc.so.1`optimize_symtab+0x6c
> >               libproc.so.1`Pbuild_file_symtab+0x787
> >               libproc.so.1`build_map_symtab+0x36
> >               libproc.so.1`Pxlookup_by_name+0x6d
> >               libproc.so.1`Plookup_by_name+0x1c
> >               libproc.so.1`ps_pglobal_lookup+0x1a
> >               librtld_db.so.1`_rd_reset64+0x10f
> >               librtld_db.so.1`rd_reset+0x58
> >               librtld_db.so.1`rd_new+0x6d
> >               libproc.so.1`Prd_agent+0x4f
> >               libproc.so.1`Pxlookup_by_addr+0x55
> >               libproc.so.1`Plookup_by_addr+0xc
> >               libdtrace.so.1`dt_print_ustack+0x16b
> >               libdtrace.so.1`dt_consume_cpu+0x3ae
> >               libdtrace.so.1`dt_consume_begin+0x92
>                ===> The library is not runnable by itself,
> why the function comes from library?
> >
> >   0  59753                        brk:entry
> >               libc.so.1`_brk_unlocked+0xa
> >               libc.so.1`sbrk+0x20
> >               libc.so.1`_morecore+0x27
> >               libc.so.1`_malloc_unlocked+0x10d
> >               libc.so.1`malloc+0x2d
> >               libproc.so.1`optimize_symtab+0x6c
> >               libproc.so.1`Pbuild_file_symtab+0x787
> >               libproc.so.1`build_map_symtab+0x36
> >               libproc.so.1`Pxlookup_by_addr+0x70
> >               libproc.so.1`Plookup_by_addr+0xc
> >               libdtrace.so.1`dt_print_ustack+0x16b
> >               libdtrace.so.1`dt_consume_cpu+0x3ae
> >               libdtrace.so.1`dt_consume_begin+0x92
> >               libdtrace.so.1`dtrace_consume+0x114
> >               libdtrace.so.1`dtrace_work+0xaa
> >               dtrace`main+0x902
> >               dtrace`_start+0x6c
>                        ==> This one is better to
> understand:  dtrace is a process calling some library, so it makes sense to
> have the "dtrace`_start+0x6c" as the outer most function.
> >
>
>
> _______________________________________________
> dtrace-discuss mailing list
> dtrace-discuss@opensolaris.org
>
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