[PATCH 1/1] perf top: Don't pass an ERR_PTR() directly to perf_session__delete()

[Arnaldo Carvalho de Melo]

While debugging a segfault on 'perf lock contention' without an
available perf.data file I noticed that it was basically calling:

	perf_session__delete(ERR_PTR(-1))

Resulting in:

  (gdb) run lock contention
  Starting program: /root/bin/perf lock contention
  [Thread debugging using libthread_db enabled]
  Using host libthread_db library "/lib64/libthread_db.so.1".
  failed to open perf.data: No such file or directory  (try 'perf record' first)
  Initializing perf session failed

  Program received signal SIGSEGV, Segmentation fault.
  0x00000000005e7515 in auxtrace__free (session=0xffffffffffffffff) at util/auxtrace.c:2858
  2858		if (!session->auxtrace)
  (gdb) p session
  $1 = (struct perf_session *) 0xffffffffffffffff
  (gdb) bt
  #0  0x00000000005e7515 in auxtrace__free (session=0xffffffffffffffff) at util/auxtrace.c:2858
  #1  0x000000000057bb4d in perf_session__delete (session=0xffffffffffffffff) at util/session.c:300
  #2  0x000000000047c421 in __cmd_contention (argc=0, argv=0x7fffffffe200) at builtin-lock.c:2161
  #3  0x000000000047dc95 in cmd_lock (argc=0, argv=0x7fffffffe200) at builtin-lock.c:2604
  #4  0x0000000000501466 in run_builtin (p=0xe597a8 <commands+552>, argc=2, argv=0x7fffffffe200) at perf.c:322
  #5  0x00000000005016d5 in handle_internal_command (argc=2, argv=0x7fffffffe200) at perf.c:375
  #6  0x0000000000501824 in run_argv (argcp=0x7fffffffe02c, argv=0x7fffffffe020) at perf.c:419
  #7  0x0000000000501b11 in main (argc=2, argv=0x7fffffffe200) at perf.c:535
  (gdb)

So just set it to NULL after using PTR_ERR(session) to decode the error
as perf_session__delete(NULL) is supported.

Fixes: 6ef81c55a2b6584c ("perf session: Return error code for perf_session__new() function on failure")
Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Alexey Budankov <alexey.budankov@xxxxxxxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Jeremie Galarneau <jeremie.galarneau@xxxxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Kate Stewart <kstewart@xxxxxxxxxxxxxxxxxxx>
Cc: Mamatha Inamdar <mamatha4@xxxxxxxxxxxxxxxxxx>
Cc: Mukesh Ojha <mojha@xxxxxxxxxxxxxx>
Cc: Nageswara R Sastry <rnsastry@xxxxxxxxxxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Ravi Bangoria <ravi.bangoria@xxxxxxxxxxxxx>
Cc: Shawn Landden <shawn@xxxxxxx>
Cc: Song Liu <songliubraving@xxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Tzvetomir Stoyanov <tstoyanov@xxxxxxxxxx>
Link: https://lore.kernel.org/lkml/
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 tools/perf/builtin-top.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index 1baa2acb3cedd989..ea8c7eca5eeedd76 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -1805,6 +1805,7 @@ int cmd_top(int argc, const char **argv)
 	top.session = perf_session__new(NULL, NULL);
 	if (IS_ERR(top.session)) {
 		status = PTR_ERR(top.session);
+		top.session = NULL;
 		goto out_delete_evlist;
 	}
 
-- 
2.37.1