Messages in this thread | | | Date | Wed, 8 May 2024 10:14:31 +0100 | Subject | Re: [PATCH 3/4] perf symbols: Update kcore map before merging in remaining symbols | From | James Clark <> |
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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 >>
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