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[PATCH] perf report: Fix sort__sym_cmp to also compare end of symbol

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  [PATCH] perf report: Fix sort__sym_cmp to also compare end of symbol Yannick Brosseau <scientist@fb.com> - 2015-06-18 01:50 +0200
    Re: [PATCH] perf report: Fix sort__sym_cmp to also compare end of  symbol Yannick Brosseau <scientist@fb.com> - 2015-06-18 02:00 +0200
    Re: [PATCH] perf report: Fix sort__sym_cmp to also compare end of  symbol Jeff Epler <jepler@unpythonic.net> - 2015-06-18 02:00 +0200

#1167482 — [PATCH] perf report: Fix sort__sym_cmp to also compare end of symbol

When using a map file from a JIT, due to memory reuse, we can
obtain multiple symbols with the same start address but a different
length.
The symbols__find does check for the end so not doing it in sort__sym_cmp
was causing the hist_entry in the annotate part of a report to match to the
wrong entry, causing a fatal error.

Signed-off-by: Yannick Brosseau <scientist@fb.com>
---
 tools/perf/util/sort.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/tools/perf/util/sort.c b/tools/perf/util/sort.c
index 4593f36..e226118 100644
--- a/tools/perf/util/sort.c
+++ b/tools/perf/util/sort.c
@@ -182,18 +182,16 @@ static int64_t _sort__addr_cmp(u64 left_ip, u64 right_ip)
 
 static int64_t _sort__sym_cmp(struct symbol *sym_l, struct symbol *sym_r)
 {
-	u64 ip_l, ip_r;
-
 	if (!sym_l || !sym_r)
 		return cmp_null(sym_l, sym_r);
 
 	if (sym_l == sym_r)
 		return 0;
 
-	ip_l = sym_l->start;
-	ip_r = sym_r->start;
+	if (sym_l->start != sym_r->start)
+		return (int64_t)(sym_r->start - sym_l->start);
 
-	return (int64_t)(ip_r - ip_l);
+	return (int64_t)(sym_r->end - sym_l->end);
 }
 
 static int64_t
-- 
2.1.4

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#1167486 — Re: [PATCH] perf report: Fix sort__sym_cmp to also compare end of symbol

On 06/17/2015 04:53 PM, Jeff Epler wrote:
> On Wed, Jun 17, 2015 at 04:41:10PM -0700, Yannick Brosseau wrote:
>> When using a map file from a JIT, due to memory reuse, we can
>> obtain multiple symbols with the same start address but a different
>> length.
> Is there some reason it's impossible for the reused memory to have the
> same length / end address?
>
It's possible that they are the same, and in that case the function
returns 0.
The patch is adding the handling of the case where they are different.


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#1167495 — Re: [PATCH] perf report: Fix sort__sym_cmp to also compare end of symbol

On Wed, Jun 17, 2015 at 04:41:10PM -0700, Yannick Brosseau wrote:
> When using a map file from a JIT, due to memory reuse, we can
> obtain multiple symbols with the same start address but a different
> length.

Is there some reason it's impossible for the reused memory to have the
same length / end address?

Jeff
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