Re: [PATCH 09/12] perf tools: Fix map reference counting

From: Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>
To: Jiri Olsa <jolsa@kernel.org>
Cc: Song Liu <songliubraving@fb.com>,
	lkml <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@kernel.org>,
	Namhyung Kim <namhyung@kernel.org>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Andi Kleen <ak@linux.intel.com>,
	Adrian Hunter <adrian.hunter@intel.com>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Eric Saint-Etienne <eric.saint.etienne@oracle.com>
Subject: Re: [PATCH 09/12] perf tools: Fix map reference counting
Date: Tue, 16 Apr 2019 16:36:45 -0300	[thread overview]
Message-ID: <20190416193645.GD9247@kernel.org> (raw)
In-Reply-To: <20190416160127.30203-10-jolsa@kernel.org>

Em Tue, Apr 16, 2019 at 06:01:24PM +0200, Jiri Olsa escreveu:
> By calling maps__insert we assume to get 2 references
> on the map, which we relese within maps__remove call.
> 
> However if there's already same map name, we currently
> don't bump the reference and can crash, like:
> 
>   Program received signal SIGABRT, Aborted.
>   0x00007ffff75e60f5 in raise () from /lib64/libc.so.6
> 
>   (gdb) bt
>   #0  0x00007ffff75e60f5 in raise () from /lib64/libc.so.6
>   #1  0x00007ffff75d0895 in abort () from /lib64/libc.so.6
>   #2  0x00007ffff75d0769 in __assert_fail_base.cold () from /lib64/libc.so.6
>   #3  0x00007ffff75de596 in __assert_fail () from /lib64/libc.so.6
>   #4  0x00000000004fc006 in refcount_sub_and_test (i=1, r=0x1224e88) at tools/include/linux/refcount.h:131
>   #5  refcount_dec_and_test (r=0x1224e88) at tools/include/linux/refcount.h:148
>   #6  map__put (map=0x1224df0) at util/map.c:299
>   #7  0x00000000004fdb95 in __maps__remove (map=0x1224df0, maps=0xb17d80) at util/map.c:953
>   #8  maps__remove (maps=0xb17d80, map=0x1224df0) at util/map.c:959
>   #9  0x00000000004f7d8a in map_groups__remove (map=<optimized out>, mg=<optimized out>) at util/map_groups.h:65
>   #10 machine__process_ksymbol_unregister (sample=<optimized out>, event=0x7ffff7279670, machine=<optimized out>) at util/machine.c:728
>   #11 machine__process_ksymbol (machine=<optimized out>, event=0x7ffff7279670, sample=<optimized out>) at util/machine.c:741
>   #12 0x00000000004fffbb in perf_session__deliver_event (session=0xb11390, event=0x7ffff7279670, tool=0x7fffffffc7b0, file_offset=13936) at util/session.c:1362
>   #13 0x00000000005039bb in do_flush (show_progress=false, oe=0xb17e80) at util/ordered-events.c:243
>   #14 __ordered_events__flush (oe=0xb17e80, how=OE_FLUSH__ROUND, timestamp=<optimized out>) at util/ordered-events.c:322
>   #15 0x00000000005005e4 in perf_session__process_user_event (session=session@entry=0xb11390, event=event@entry=0x7ffff72a4af8,
>   ...
> 
> Adding the map on the list and getting the reference event
> if we find the map with same name.

Added:

Fixes: 1e6285699b30 ("perf symbols: Fix slowness due to -ffunction-section")

Ccing Eric Saint-Etienne <eric.saint.etienne@oracle.com>, the author of
the patch that introduced that function.

And applied to perf/urgent

> Cc: Song Liu <songliubraving@fb.com>
> Link: http://lkml.kernel.org/n/tip-38t1ihcy32lvu4xfpm0p7yex@git.kernel.org
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---
>  tools/perf/util/map.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c
> index 28d484ef74ae..ee71efb9db62 100644
> --- a/tools/perf/util/map.c
> +++ b/tools/perf/util/map.c
> @@ -926,10 +926,8 @@ static void __maps__insert_name(struct maps *maps, struct map *map)
>  		rc = strcmp(m->dso->short_name, map->dso->short_name);
>  		if (rc < 0)
>  			p = &(*p)->rb_left;
> -		else if (rc  > 0)
> -			p = &(*p)->rb_right;
>  		else
> -			return;
> +			p = &(*p)->rb_right;
>  	}
>  	rb_link_node(&map->rb_node_name, parent, p);
>  	rb_insert_color(&map->rb_node_name, &maps->names);
> -- 
> 2.17.2

-- 

- Arnaldo