I'm not fully sure if this is the correct fix, but without this I get
crashes on more complex perf stat metric usages. The problem is that
part of the state gets freed when a weak group fails, but then is later
still used. Just don't free the ids, we're going to reuse them anyways
on the weak group retry.

For example:

  % perf stat -M IpB,IpCall,IpTB,IPC,Retiring_SMT,Frontend_Bound_SMT,Kernel_Utilization,CPU_Utilization --metric-only -a -I 1000 sleep 2

  crashes and gives in valgrind:

  =21527== Invalid write of size 8
  ==21527==    at 0x4EE582: hlist_add_head (list.h:644)
  ==21527==    by 0x4EFD3C: perf_evlist__id_hash (evlist.c:477)
  ==21527==    by 0x4EFD99: perf_evlist__id_add (evlist.c:483)
  ==21527==    by 0x4EFF15: perf_evlist__id_add_fd (evlist.c:524)
  ==21527==    by 0x4FC693: store_evsel_ids (evsel.c:2969)
  ==21527==    by 0x4FC76C: perf_evsel__store_ids (evsel.c:2986)
  ==21527==    by 0x450DA7: __run_perf_stat (builtin-stat.c:519)
  ==21527==    by 0x451285: run_perf_stat (builtin-stat.c:636)
  ==21527==    by 0x454619: cmd_stat (builtin-stat.c:1966)
  ==21527==    by 0x4D557D: run_builtin (perf.c:310)
  ==21527==    by 0x4D57EA: handle_internal_command (perf.c:362)
  ==21527==    by 0x4D5931: run_argv (perf.c:406)
  ==21527==  Address 0x12e3f008 is 104 bytes inside a block of size 2,056 free'd
  ==21527==    at 0x4839A0C: free (vg_replace_malloc.c:540)
  ==21527==    by 0x627139: xyarray__delete (xyarray.c:32)
  ==21527==    by 0x4F6BE4: perf_evsel__free_id (evsel.c:1253)
  ==21527==    by 0x4FA11F: evsel__close (evsel.c:1994)
  ==21527==    by 0x4F30A3: perf_evlist__reset_weak_group (evlist.c:1783)
  ==21527==    by 0x450B47: __run_perf_stat (builtin-stat.c:466)
  ==21527==    by 0x451285: run_perf_stat (builtin-stat.c:636)
  ==21527==    by 0x454619: cmd_stat (builtin-stat.c:1966)
  ==21527==    by 0x4D557D: run_builtin (perf.c:310)
  ==21527==    by 0x4D57EA: handle_internal_command (perf.c:362)
  ==21527==    by 0x4D5931: run_argv (perf.c:406)
  ==21527==    by 0x4D5CAE: main (perf.c:531)
  ==21527==  Block was alloc'd at
  ==21527==    at 0x483AB1A: calloc (vg_replace_malloc.c:762)
  ==21527==    by 0x627024: zalloc (zalloc.c:8)
  ==21527==    by 0x627088: xyarray__new (xyarray.c:10)
  ==21527==    by 0x4F6B20: perf_evsel__alloc_id (evsel.c:1237)
  ==21527==    by 0x4FC74E: perf_evsel__store_ids (evsel.c:2983)
  ==21527==    by 0x450DA7: __run_perf_stat (builtin-stat.c:519)
  ==21527==    by 0x451285: run_perf_stat (builtin-stat.c:636)
  ==21527==    by 0x454619: cmd_stat (builtin-stat.c:1966)
  ==21527==    by 0x4D557D: run_builtin (perf.c:310)
  ==21527==    by 0x4D57EA: handle_internal_command (perf.c:362)
  ==21527==    by 0x4D5931: run_argv (perf.c:406)
  ==21527==    by 0x4D5CAE: main (perf.c:531)
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Link: http://lore.kernel.org/lkml/20190923233339.25326-1-andi@firstfloor.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>