[Crash-utility] [PATCH] crash: Do not use bt -t flag in panic_search()

[Michael Holzheu]

Hi Dave,

I got a dump where a process "gmain" was incorrectly marked as running:

crash> ps | grep gmain
>   217      1   5      8bec23420     IN   0.0  463276  18240  gmain

The reason was that the "brute force" way parsing the "bt -t -o"
output in panic_search() found the symbol "panic" on the stack:

crash> bt -t -o 8bec23420
PID: 217    TASK: 8bec23420         CPU: 5   COMMAND: "gmain"
              START: __schedule at 83f650
  [       8b662b900] (null) at 0
  [       8b662b950] (null) at 0
  [       8b662b978] __schedule at 83f650
  [       8b662b990] (null) at 0
...
  [       8b662bb18] (null) at 0
  [       8b662bb40] panic at 83679a  <<<<<--------------
  [       8b662bb58] _ehead at 280da

The real stack trace was as follows:

crash> bt  8bec23420
Detaching after fork from child process 15508.
PID: 217    TASK: 8bec23420         CPU: 5   COMMAND: "gmain"
 #0 [8b662b8f0] __schedule at 83f650
 #1 [8b662b958] schedule at 83fade
 #2 [8b662b970] schedule_hrtimeout_range_clock at 842fc8
 #3 [8b662ba10] poll_schedule_timeout at 2c6e8a
 #4 [8b662ba30] do_sys_poll at 2c8604
 #5 [8b662be40] sys_poll at 2c8852
 #6 [8b662bea8] system_call at 843a66

IMHO the "-t" method is quite risky (at least on s390). What about using
the "normal" stack backtrace without the "-t" bt option?
---
 task.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/task.c
+++ b/task.c
@@ -6633,7 +6633,7 @@ panic_search(void)
         fd = &foreach_data;
 	fd->keys = 1;
 	fd->keyword_array[0] = FOREACH_BT; 
-	fd->flags |= (FOREACH_t_FLAG|FOREACH_o_FLAG);
+	fd->flags |= FOREACH_o_FLAG;
 
 	dietask = lasttask = NO_TASK;
 	
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