Ah, it must be because of the common user-kernel virtual address space on s390x? I can accept a patch if it's s390 only.
Dave
Sent from my Verizon Wireless 4G LTE smartphone
-------- Original message --------
From: Dave Anderson <anderson@xxxxxxxxxx>
Date: 08/03/2015 11:18 AM (GMT-05:00)
To: Michael Holzheu <holzheu@xxxxxxxxxxxxxxxxxx>
Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx>, "Discussion list for crash utility usage, maintenance and development" <crash-utility@xxxxxxxxxx>
Subject: Re: [Crash-utility] [PATCH] crash: Do not use bt -t flag in panic_search()
----- Original Message -----
> 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
I guess the obvious question is why "panic" was on the stack?
>
> 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?
That really worries me -- introducing the usage of normal backtrace on all tasks
instead of simply walking the stack memory looking for text addresses is a huge
change.
Dave
> ---
> 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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