[Crash-utility] Crash in crash

Thu Oct 23 05:38:40 UTC 2014

Fine. If you remove that message then I see no problems with your 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 22 oktober 2014 15:02
To: Discussion list for crash utility usage, maintenance and development
Subject: Re: [Crash-utility] Crash in crash

----- Original Message -----
> 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

Yeah, that message will be removed in crash-7.0.9:

  https://github.com/crash-utility/crash/commit/a3a441aeabd6c5c3c86b4793a283927507a5cc10

The point of the matter is to entirely avoid doing initial sort, and then doing the RSS gathering and associated readmem()'s for all tasks during the last-ditch panic-task search that your dumpfile requires.

Dave

> 
> 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
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> > --
> > Crash-utility mailing list
> > Crash-utility at redhat.com
> > https://www.redhat.com/mailman/listinfo/crash-utility
> 
> --
> Crash-utility mailing list
> Crash-utility at redhat.com
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> 

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