reimplementation of smp_call_function example from OLS

[William Cohen <wcohen at redhat dot com>]

Playing around with the instrumentation I attempted to reimplement the 
example given in the OLS 2005 presenation so that it works with the 
current translator. The attached scf.stp appears to work. Below is the 
output.

Things that strike me about this example:
1) Outputting data could be simpler
2) Sorting the data would be useful. I should take a look at Tom's 
kmalloc-top example that he checked in for sorting.
3) It appears that some backtraces are truncated.

-Will

 stap scf.stp
start of data collection
end of data collection
traces[2234,hald,
 0xc0114d67 : smp_call_function+0x10/0xfa
 0xc016a6af : invalidate_bh_lrus+0x1b/0x22
 0xc01697ca : invalidate_bdev+0x8/0x17
 0xc0180649 : __invalidate_device+0x30/0x36
 0xc016fb46 : check_disk_change+0x2b/0x66
 0xc0256908 : get_disk+0x1d/0x7d
 0xc028511e : cdrom_open+0x62/0xdb
 0xc024da4e : kobj_lookup+0x152/0x196
 0xc0281f1b : idecd_open+0x45/0x8f
 0xc016fc81 : do_open+0x8f/0x343
 0xc016ffad : blkdev_open+0x1a/0x4a
 0xc01672c2 : dentry_open+0xcf/0x1e9
 0xc01671ed : filp_open+0x40/0x46
 0xc015161f : cache_alloc_debugcheck_after+0x31/0x129
 0xc
] = 105
traces[2234,hald,
 0xc0114d67 : smp_call_function+0x10/0xfa
 0xc016a6af : invalidate_bh_lrus+0x1b/0x22
 0xc01697ca : invalidate_bdev+0x8/0x17
 0xc016f2b5 : kill_bdev+0xd/0x20
 0xc017012c : blkdev_put+0x14f/0x164
 0xc0168ddd : __fput+0xb1/0x18f
 0xc016764e : filp_close+0x3e/0x62
 0xc01039d1 : syscall_call+0x7/0xb
] = 104
traces[2234,hald,
 0xc0114d67 : smp_call_function+0x10/0xfa
 0xc0104416 : common_interrupt+0x1a/0x20
 0xc016a6af : invalidate_bh_lrus+0x1b/0x22
 0xc01697ca : invalidate_bdev+0x8/0x17
 0xc016f2b5 : kill_bdev+0xd/0x20
 0xc017012c : blkdev_put+0x14f/0x164
 0xc0168ddd : __fput+0xb1/0x18f
 0xc016764e : filp_close+0x3e/0x62
 0xc01039d1 : syscall_call+0x7/0xb
] = 1

# scf.stp
# A reimplementation of user script:smp_call_function example given at OLS 2005
# in the current language.
#
# Will Cohen

global traces

probe kernel.function("smp_call_function") 
{
  traces[pid(), pexecname(), backtrace()] += 1;
}

probe end {
  log("end of data collection");
  foreach( [pid, name, stack] in traces){
    log( "traces[" . string(pid) . "," . name . "," );
    print_stack(stack)
    log( "] = " . string(traces[pid, name, stack]) );
  }
}

probe begin { log("start of data collection"); }