Messages in this thread | | | Date | Thu, 6 Jan 2022 17:34:08 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH 01/20] perf nsinfo: fix refcounting |
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Em Thu, Jan 06, 2022 at 05:27:43PM -0300, Arnaldo Carvalho de Melo escreveu: > Em Tue, Jan 04, 2022 at 10:19:42PM -0800, Krister Johansen escreveu: > > On Thu, Jul 15, 2021 at 04:20:24PM -0300, Arnaldo Carvalho de Melo wrote: > > > Em Thu, Jul 15, 2021 at 04:02:16PM -0300, Arnaldo Carvalho de Melo escreveu: > > > > Em Thu, Jul 15, 2021 at 06:07:06PM +0200, Riccardo Mancini escreveu: > > > > > ASan reports a memory leak of nsinfo during the execution of the perf > > > > > test "31: Lookup mmap thread". > > > > > The leak is caused by a refcounted variable being replaced without > > > > > dropping the refcount. > > > > > > > > This patch makes sure that the refcnt of nsinfo is decreased whenever > > > > > a refcounted variable is replaced with a new value. > > > > > > > So, there are multiple fixes in just one patch, I'll split it into > > > > three, no need to resend. > > > > > > > I'll try and check if finding Fixes: for the three is easy, that way > > > > stable@vger.kernel.org will figure out which of the supported releases > > > > need each of them. > > > > > > The second is at the end of this message, and looking at it I think > > > there is a problem with where this nsinfo reference is stored, it should > > > be in the 'struct map', that is per-thread, not in the 'struct dso', > > > that may be shared by multiple 'struct map's in different cgroups, so we > > > can't set dso->nsinfo in map__new(), right? Kristen? > > > > Apologies for the long delayed reply, and for the hassle that this has > > caused. > > > > You're right, Arnaldo, that namespace mapping could differ on a per > > thread basis. If the dso objects are intended to be read by multiple > > threads with different views of the target process's namespaces. With > > containers, though, there might be many different versions of the same > > object with the same filename, and the only ways we can disambiguate are > > through the build-ids or by ensuring that the dso refers to a single > > pid and mount namespace. I may have erred in assuming that all of > > perf's threads would be able to access the target namespace via the same > > identifiers. Is that what's going on here? > > yeah, I think using build-ids, when available is the way to go, and > since we can almost take it for granted (haven't checked) that it will > be present, as I think gcc/clang adds them by default, seems the way to > go. > > That or somehow have the DSO list to be perf namespace.
To be by namespace, sorry.
But having it by build-id seems the more sensible way to go, so that we can avoid having multiple instances of the same DSO in multiple namespaces, which should be common.
I.e. continue to have a perf 'struct machine' DSO list instead of moving to having the namespace hierarchy represented under 'struct machine' since we have a way to uniquify DSOs, the build id.
One way or the other, nsinfo shouldn't be stored in DSOs, its a map property, which in turn is a thread property.
I.e. please consider thinking about moving it to 'struct map', would you try it, please?
- Arnaldo
> - Arnaldo > > > -K > > > > > > > commit 280f3933661f9ca9563ed04ce82313fdbcbb8f75 > > > Author: Riccardo Mancini <rickyman7@gmail.com> > > > Date: Thu Jul 15 18:07:06 2021 +0200 > > > > > > perf map: Fix dso->nsinfo refcounting > > > > > > ASan reports a memory leak of nsinfo during the execution of > > > > > > # perf test "31: Lookup mmap thread" > > > > > > The leak is caused by a refcounted variable being replaced without > > > dropping the refcount. > > > > > > This patch makes sure that the refcnt of nsinfo is decreased whenever a > > > refcounted variable is replaced with a new value. > > > > > > Signed-off-by: Riccardo Mancini <rickyman7@gmail.com> > > > Fixes: bf2e710b3cb8445c ("perf maps: Lookup maps in both intitial mountns and inner mountns.") > > > Cc: Ian Rogers <irogers@google.com> > > > Cc: Jiri Olsa <jolsa@redhat.com> > > > Cc: Krister Johansen <kjlx@templeofstupid.com> > > > Cc: Mark Rutland <mark.rutland@arm.com> > > > Cc: Namhyung Kim <namhyung@kernel.org> > > > Cc: Peter Zijlstra <peterz@infradead.org> > > > Link: http://lore.kernel.org/lkml/55223bc8821b34ccb01f92ef1401c02b6a32e61f.1626343282.git.rickyman7@gmail.com > > > Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> > > > > > > diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c > > > index 8af693d9678cefe0..72e7f3616157ead4 100644 > > > --- a/tools/perf/util/map.c > > > +++ b/tools/perf/util/map.c > > > @@ -192,6 +192,8 @@ struct map *map__new(struct machine *machine, u64 start, u64 len, > > > if (!(prot & PROT_EXEC)) > > > dso__set_loaded(dso); > > > } > > > + > > > + nsinfo__put(dso->nsinfo); > > > dso->nsinfo = nsi; > > > > > > if (build_id__is_defined(bid)) > > > > > -- > > - Arnaldo
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- Arnaldo
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