lkml.org 
[lkml]   [2024]   [May]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH 3/4] perf symbols: Update kcore map before merging in remaining symbols
From


On 08/05/2024 05:10, Namhyung Kim wrote:
> On Tue, May 7, 2024 at 7:13 AM James Clark <james.clark@arm.com> wrote:
>>
>> When loading kcore, the main vmlinux map is updated in the same loop
>> that merges the remaining maps. If a map that overlaps is merged in
>> before kcore, the list can become unsortable when the main map addresses
>> are updated. This will later trigger the check_invariants() assert:
>>
>> $ perf record
>> $ perf report
>>
>> util/maps.c:96: check_invariants: Assertion `map__end(prev) <=
>> map__start(map) || map__start(prev) == map__start(map)' failed.
>> Aborted
>>
>> Fix it by moving the main map update prior to the loop so that
>> maps__merge_in() can split it if necessary.
>
> Looks like you and Leo are working on the same problem.
>
> https://lore.kernel.org/r/20240505202805.583253-1-leo.yan@arm.com/
>

Oops I should have checked the list. It looks like we can still take his
fix as well though, with an updated comment.

>>
>> Fixes: 659ad3492b91 ("perf maps: Switch from rbtree to lazily sorted array for addresses")
>> Signed-off-by: James Clark <james.clark@arm.com>
>> ---
>> tools/perf/util/symbol.c | 40 +++++++++++++++++++++-------------------
>> 1 file changed, 21 insertions(+), 19 deletions(-)
>>
>> diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
>> index 2d95f22d713d..e98dfe766da3 100644
>> --- a/tools/perf/util/symbol.c
>> +++ b/tools/perf/util/symbol.c
>> @@ -1289,7 +1289,7 @@ static int dso__load_kcore(struct dso *dso, struct map *map,
>> {
>> struct maps *kmaps = map__kmaps(map);
>> struct kcore_mapfn_data md;
>> - struct map *replacement_map = NULL;
>> + struct map *map_ref, *replacement_map = NULL;
>> struct machine *machine;
>> bool is_64_bit;
>> int err, fd;
>> @@ -1367,6 +1367,24 @@ static int dso__load_kcore(struct dso *dso, struct map *map,
>> if (!replacement_map)
>> replacement_map = list_entry(md.maps.next, struct map_list_node, node)->map;
>>
>> + /*
>> + * Update addresses of vmlinux map. Re-insert it to ensure maps are
>> + * correctly ordered. Do this before using maps__merge_in() for the
>> + * remaining maps so vmlinux gets split if necessary.
>> + */
>> + map_ref = map__get(map);
>> + maps__remove(kmaps, map_ref);
>
> A nitpick. It'd be natural to use 'map' instead of 'map_ref'
> (even if they are the same) since IIUC we want to remove
> the old 'map' and update 'map_ref' then add it back.
>

Using map makes sense, I can update that.

>> +
>> + map__set_start(map_ref, map__start(replacement_map));
>> + map__set_end(map_ref, map__end(replacement_map));
>> + map__set_pgoff(map_ref, map__pgoff(replacement_map));
>> + map__set_mapping_type(map_ref, map__mapping_type(replacement_map));
>
> So here, replacement_map should not be NULL right?
>

Yes it shouldn't be. It would only be NULL if md.maps is empty, but
there's already an exit condition for that above.

Some of the other code also assumes node->map is always set, so it can't
be NULL that way either.

> Thanks,
> Namhyung
>
>> +
>> + err = maps__insert(kmaps, map_ref);
>> + map__put(map_ref);
>> + if (err)
>> + goto out_err;
>> +
>> /* Add new maps */
>> while (!list_empty(&md.maps)) {
>> struct map_list_node *new_node = list_entry(md.maps.next, struct map_list_node, node);
>> @@ -1374,24 +1392,8 @@ static int dso__load_kcore(struct dso *dso, struct map *map,
>>
>> list_del_init(&new_node->node);
>>
>> - if (RC_CHK_EQUAL(new_map, replacement_map)) {
>> - struct map *map_ref;
>> -
>> - /* Ensure maps are correctly ordered */
>> - map_ref = map__get(map);
>> - maps__remove(kmaps, map_ref);
>> -
>> - map__set_start(map_ref, map__start(new_map));
>> - map__set_end(map_ref, map__end(new_map));
>> - map__set_pgoff(map_ref, map__pgoff(new_map));
>> - map__set_mapping_type(map_ref, map__mapping_type(new_map));
>> -
>> - err = maps__insert(kmaps, map_ref);
>> - map__put(map_ref);
>> - map__put(new_map);
>> - if (err)
>> - goto out_err;
>> - } else {
>> + /* skip if replacement_map, already inserted above */
>> + if (!RC_CHK_EQUAL(new_map, replacement_map)) {
>> /*
>> * Merge kcore map into existing maps,
>> * and ensure that current maps (eBPF)
>> --
>> 2.34.1
>>

\
 
 \ /
  Last update: 2024-05-08 11:14    [W:0.057 / U:0.892 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site