On 03/03/2022 11:36, Jiri Olsa wrote:
On Wed, Mar 02, 2022 at 04:20:00PM +0000, James Clark wrote:
On 27/02/2022 22:50, Jiri Olsa wrote:
On Thu, Feb 24, 2022 at 05:19:55PM +0000, James Clark wrote:
MMAP records that occur after the build-id header is parsed do not have their build-id set even if the filename matches an entry from the header. Set the build-id on these dsos as long as the MMAP record doesn't have its own build-id set.
This fixes an issue with off target analysis where the local version of a dso is loaded rather than one from ~/.debug via a build-id.
nice catch :)
Reported-by: Denis Nikitin denik@chromium.org Signed-off-by: James Clark james.clark@arm.com
tools/perf/util/dso.h | 1 + tools/perf/util/header.c | 1 + tools/perf/util/map.c | 16 ++++++++++++++-- 3 files changed, 16 insertions(+), 2 deletions(-)
diff --git a/tools/perf/util/dso.h b/tools/perf/util/dso.h index 011da3924fc1..3a9fd4d389b5 100644 --- a/tools/perf/util/dso.h +++ b/tools/perf/util/dso.h @@ -167,6 +167,7 @@ struct dso { enum dso_load_errno load_errno; u8 adjust_symbols:1; u8 has_build_id:1;
- u8 header_build_id:1; u8 has_srcline:1; u8 hit:1; u8 annotate_warned:1;
diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c index 6da12e522edc..571d73d4f976 100644 --- a/tools/perf/util/header.c +++ b/tools/perf/util/header.c @@ -2200,6 +2200,7 @@ static int __event_process_build_id(struct perf_record_header_build_id *bev, build_id__init(&bid, bev->data, size); dso__set_build_id(dso, &bid);
dso->header_build_id = 1;if (dso_space != DSO_SPACE__USER) { struct kmod_path m = { .name = NULL, }; diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c index 1803d3887afe..4ae91e491e23 100644 --- a/tools/perf/util/map.c +++ b/tools/perf/util/map.c @@ -127,7 +127,7 @@ struct map *map__new(struct machine *machine, u64 start, u64 len, if (map != NULL) { char newfilename[PATH_MAX];
struct dso *dso;
struct dso *dso, *header_bid_dso;android = is_android_lib(filename); @@ -185,7 +185,19 @@ struct map *map__new(struct machine *machine, u64 start, u64 len, if (build_id__is_defined(bid)) dso__set_build_id(dso, bid);
else {nit please add { } to the if clause as well
/** If the mmap event had no build ID, search for an existing dso from the* build ID header by name. Otherwise only the dso loaded at the time of* reading the header will have the build ID set and all future mmaps will* have it missing.*/header_bid_dso = __dsos__find(&machine->dsos, filename, false);is this 'perf top' safe? I think dso should be added in the same thread, but please check and add comment why we don't need locking in here
Seems like there are multiple synthesize_threads_workers using the same machine->dsos object so I think locking is needed.
At first I thought of doing this:
diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c index 4ae91e491e23..b87b81e3d41c 100644 --- a/tools/perf/util/map.c +++ b/tools/perf/util/map.c @@ -192,7 +192,9 @@ struct map *map__new(struct machine *machine, u64 start, u64 len, * reading the header will have the build ID set and all future mmaps will * have it missing. */
down_read(&machine->dsos.lock); header_bid_dso = __dsos__find(&machine->dsos, filename, false);up_read(&machine->dsos.lock); if (header_bid_dso && header_bid_dso->header_build_id) { dso__set_build_id(dso, &header_bid_dso->bid); dso->header_build_id = 1;But then I was wondering why it doesn't need a write lock all the way from machine__findnew_dso_id() to dso__put()? At the moment there are writes to the dso like dso__set_loaded(), dso->nsinfo = nsi and dso__set_build_id(), so another thread could find the dso in a partially constructed state.
I think that's fine, machine__findnew_dso_id takes the dso ref so the real 'release' is when the machine object goes down at dsos__purge
Not sure if this is an issue currently without my patch, but at least with it they would have to be found with header_build_id already set to 1 otherwise it will mess things up.
as for the partial changes I think it's also fine, because it happens at separate places.. we'd need to investigate specific example to see if there's a problem
Extending the write lock outside of machine__findnew_dso_id() is difficult because it already releases it before it returns. Does it need to be changed so that machine__findnew_dso_id() takes all the arguments needed to construct it inside the lock?
the change above should do it.. as for top threads I don't think it actually matters because there's events processing and hists processing, and I did not find them clashing in this.. but there's some setup session code that touches this, so it's better to be safe
Ok yes I think I agree. The header flag isn't important for perf top so having it all constructed in place isn't necessary.
I've submitted v2 with this change.
Thanks for the review.
thanks, jirka
-
James Clark