[Crash-utility] Crash in crash

[Karlsson, Jan]

Hi

Your patch works but I get a "strange" error message:

please wait... (determining panic task)         
bt: bsearch for tgid failed: task: ffffffc01cfed400 tgid: 5040

      KERNEL: vmlinux                   
    DUMPFILE: vmcore
    ....

This message does not occur with my patch.

Jan

Jan Karlsson
Senior Software Engineer
System Assurance

Sony Mobile Communications
Tel: +46 703 062 174
jan.karlsson at sonymobile.com

sonymobile.com



-----Original Message-----
From: crash-utility-bounces at redhat.com [mailto:crash-utility-bounces at redhat.com] On Behalf Of Dave Anderson
Sent: den 21 oktober 2014 16:32
To: Discussion list for crash utility usage, maintenance and development
Subject: Re: [Crash-utility] Crash in crash


Hi Jan,

Good catch.  As far as a fix goes, it would be more efficient if
tgid_quick_search() just returns a NULL in that case.  Try the attached patch.

Thanks,
  Dave




----- Original Message -----
> 
> 
> Hi Dave
> 
> 
> 
> I have a vmcore file for ARM64 that crashes Crash during startup. The 
> core file is created at a hardware watchdog (I believe) so there is no 
> panic message or something similar in the log.
> 
> 
> 
> This is the printout from Crash running under gdb, after the 
> copyrights and config information:
> 
> 
> 
> please wait... (determining panic task)
> 
> Program received signal SIGSEGV, Segmentation fault.
> 
> 0x000000000047ed40 in tgid_quick_search (tgid=5040) at memory.c:4114
> 
> 4114 if (tgid == last->tgid) {
> 
> 
> 
> (gdb) bt
> 
> #0 0x000000000047ed40 in tgid_quick_search (tgid=5040) at 
> memory.c:4114
> 
> #1 0x000000000047f046 in get_task_mem_usage 
> (task=18446743799318107136,
> tm=0x7fffffff6f40)
> 
> at memory.c:4186
> 
> #2 0x000000000047c679 in vm_area_dump (task=18446743799318107136, 
> flag=10, vaddr=0, ref=0x0)
> 
> at memory.c:3671
> 
> #3 0x000000000047ec08 in in_user_stack (task=18446743799318107136, 
> vaddr=0) at memory.c:4063
> 
> #4 0x00000000004fd9fe in arm64_get_dumpfile_stackframe 
> (frame=<synthetic
> pointer>,
> 
> bt=<optimized out>) at arm64.c:1077
> 
> #5 arm64_get_stack_frame (bt=0x7fffffffc690, pcp=0x7fffffff9560,
> spp=0x7fffffff9568)
> 
> at arm64.c:1103
> 
> #6 0x00000000004de409 in back_trace (bt=0x7fffffffc690) at 
> kernel.c:2533
> 
> #7 0x00000000004d1563 in foreach (fd=0x7fffffffc7c0) at task.c:6161
> 
> #8 0x00000000004d2bbd in panic_search () at task.c:6425
> 
> #9 0x00000000004d4454 in get_panic_context () at task.c:5364
> 
> #10 task_init () at task.c:491
> 
> #11 0x000000000046146e in main_loop () at main.c:801
> 
> #12 0x00000000006467a3 in captured_command_loop (data=<optimized out>) 
> at
> main.c:258
> 
> #13 0x000000000064535b in catch_errors (func=0x646790 
> <captured_command_loop>, func_args=0x0,
> 
> errstring=0x873235 "", mask=6) at exceptions.c:557
> 
> #14 0x0000000000647726 in captured_main (data=<optimized out>) at 
> main.c:1064
> 
> #15 0x000000000064535b in catch_errors (func=0x646aa0 <captured_main>, 
> func_args=0x7fffffffe030,
> 
> errstring=0x873235 "", mask=6) at exceptions.c:557
> 
> #16 0x0000000000647a84 in gdb_main (args=<optimized out>) at 
> main.c:1079
> 
> #17 0x0000000000647abe in gdb_main_entry (argc=<optimized out>, 
> argv=<optimized out>)
> 
> at main.c:1099
> 
> #18 0x000000000045f61f in main (argc=3, argv=0x7fffffffe188) at 
> main.c:758
> 
> 
> 
> (gdb) p tt->last_tgid
> 
> $1 = (struct tgid_context *) 0x0
> 
> 
> 
> Source code for tgid_quick_search:
> 
> static struct tgid_context *
> 
> tgid_quick_search(ulong tgid)
> 
> {
> 
> struct tgid_context *last, *next;
> 
> 
> 
> tt->tgid_searches++;
> 
> 
> 
> last = tt->last_tgid;
> 
> if (tgid == last->tgid) {
> 
> tt->tgid_cache_hits++;
> 
> return last;
> 
> }
> 
> ....
> 
> }
> 
> 
> 
> So 'last' becomes 0 which causes the crash.
> 
> 
> 
> After some more investigation I have seen that "tt->last_tgid" is 
> initialized in function sort_tgid_array in task.c, but that function 
> seems to be called at a later stage.
> 
> 
> 
> By adding a line in tgid_quick_search:
> 
> 
> 
> static struct tgid_context *
> 
> tgid_quick_search(ulong tgid)
> 
> {
> 
> struct tgid_context *last, *next;
> 
> 
> 
> tt->tgid_searches++;
> 
> 
> 
> if (tt->last_tgid == 0) sort_tgid_array(); // added line
> 
> last = tt->last_tgid;
> 
> if (tgid == last->tgid) {
> 
> tt->tgid_cache_hits++;
> 
> return last;
> 
> }
> 
> ...
> 
> 
> 
> I can run Crash on this core file. However I do not know if this is 
> the best way to fix the problem.
> 
> 
> 
> Jan
> 
> 
> 
> Jan Karlsson
> 
> Senior Software Engineer
> 
> System Assurance
> 
> 
> 
> Sony Mobile Communications
> 
> Tel: +46 703 062 174
> 
> jan.karlsson at sonymobile.com
> 
> 
> 
> sonymobile.com
> 
> 
> 
> 
> 
> 
> 
> --
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