Re: [uml-devel] handle_trap - failed to wait at end of syscall

[Joe Marzot <gmarzot@nortelnetworks.com>]

remeber this one?...the latest take on this is that because we launch 
UMLs from a perl script (using fork/exec) when the perl script exits a 
SIGHUP is transmitted to the UML proc which sometimes interrupts a 
waitpid()...if that interruption occurs during the nullification of a 
syscall (now that I know what that means:) then you get a kernel panic 
like below.

I made a small fix that seems to be working for me and looks like what's 
going on in CATCH_EINTR

do {
   CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED));
} while (WIFSTOPPED(status) && (STOPSIG(status) == SIGHUP))

can't do this globally in CATCH_EINTR since some waitpids don't check 
status...maybe they should...maybe there is a more correct way to do 
this altogether...

thoughts?

regards, Giovanni

Marzot, Joe [BL60:NP72:EXCH] wrote:
> Joe Marzot wrote:
> 
>> here is a better one produced under similar conditions - this time the 
>> core is readable (I do get the unreadable cores quite often though).
>>
>> this is host RH8 + skas3 patch
>>
>> guest is 2.4.2x + 2.4.24-1um
> 
> 
> so looking deeper in this core in handle_trap I see the call to waitpid 
> fails with a status of 383 and an err of 13456
> 
> (gdb) p err
> $6 = 13456 (the pid of the child who exitted)
> (gdb) p status
> $7 = 383
> 
> WSTOPSIG(err) = SIGHUP
> 
> does this give any clues...any ideas of what else to look at?
> 
> thanks, GSM
> 
>>
>> [root@wbl6y227 plankton]# /usr/local/builds/gdb-6.2/gdb/gdb -c 
>> ~szhimin/tmp/joe/core.13456 
>> /view/build_neptune_dev_int144.resp3/vob/neptune/plankton/celp/linux.celp
>> GNU gdb 6.2
>> Copyright 2004 Free Software Foundation, Inc.
>> GDB is free software, covered by the GNU General Public License, and 
>> you are
>> welcome to change it and/or distribute copies of it under certain 
>> conditions.
>> Type "show copying" to see the conditions.
>> There is absolutely no warranty for GDB.  Type "show warranty" for 
>> details.
>> This GDB was configured as "i686-pc-linux-gnu"...Using host 
>> libthread_db library "/lib/libthread_db.so.1".
>>
>> Core was generated by `/vob/neptune/plankton/celp/linux.celp 
>> (DSC-0-0-0) [nameServer]                '.
>> Program terminated with signal 6, Aborted.
>> #0  0xa01643e1 in kill ()
>>     at 
>> /localdisk/builds/3pc/2.4.22-i686sim/2.4.22/include/asm/arch/string.h:486
>> 486                     case 1: COMMON("\n\tstosb"); return s;
>> (gdb) where
>> #0  0xa01643e1 in kill ()
>>     at 
>> /localdisk/builds/3pc/2.4.22-i686sim/2.4.22/include/asm/arch/string.h:486
>> #1  0xa018cbdb in raise ()
>>     at 
>> /localdisk/builds/3pc/2.4.22-i686sim/2.4.22/include/asm/arch/string.h:486
>> #2  0xa01646cd in abort ()
>>     at 
>> /localdisk/builds/3pc/2.4.22-i686sim/2.4.22/include/asm/arch/string.h:486
>> #3  0xa00d01e4 in handle_trap (pid=13461, regs=0xa5f7827c) at 
>> process.c:90
>> #4  0xa00d0438 in userspace (regs=0xa5f7827c) at process.c:168
>> #5  0xa00d0bfa in fork_handler (sig=10) at process_kern.c:102
>> #6  <signal handler called>
>> #7  0xa01643e1 in kill ()
>>     at 
>> /localdisk/builds/3pc/2.4.22-i686sim/2.4.22/include/asm/arch/string.h:486
>> #8  0xa00d4734 in os_usr1_process (pid=13456) at process.c:95
>> #9  0xa00d04ce in new_thread (stack=Cannot access memory at address 0x8
>> ) at process.c:205
>> Previous frame inner to this frame (corrupt stack?)
>> (gdb) info thr
>> * 1 process 13456  0xa01643e1 in kill ()
>>     at 
>> /localdisk/builds/3pc/2.4.22-i686sim/2.4.22/include/asm/arch/string.h:486
>> (gdb)
>>
>>
>>
> 
> 
> 
> 
> 
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