Re: Xen blktap driver for Ceph RBD : Anybody wants to test ? :p

From: Frederik Thuysbaert <frederik.thuysbaert@gmail.com>
To: Sylvain Munaut <s.munaut@whatever-company.com>
Cc: "ceph-devel@vger.kernel.org" <ceph-devel@vger.kernel.org>,
	James Harper <james.harper@bendigoit.com.au>,
	"xen-devel@lists.xen.org" <xen-devel@lists.xen.org>
Subject: Re: Xen blktap driver for Ceph RBD : Anybody wants to test ? :p
Date: Fri, 16 Aug 2013 10:27:02 +0200	[thread overview]
Message-ID: <520DE256.80400__2253.55141233212$1376655200$gmane$org@gmail.com> (raw)
In-Reply-To: <CAF6-1L43p76keEosc+RfP0yzGfFFn==b9FTUKwYSU5xski4pTw@mail.gmail.com>

Hi Sylvain,

>> I'm not quite sure what u mean, can u give some more information on how I do
>> this? I compiled tapdisk with ./configure CFLAGS=-g, but I'm not sure this
>> is what u meant.
>
> Yes, ./configure CFLAGS=-g LDFLAGS=-g  is a good start.
>
>...
>
> Then once you have a core file, you can use gdb along with the tapdisk
> executable to generate a meaningful backtrace of where the crash
>

I did 2 runs, with a cold reboot in between just to be sure. I don't 
think I'm getting a lot of valuable information, but I will post it 
anyway. The reason for the cold reboot was a 'Cannot access memory at 
address ...' in gdb after the first frame, I thought it could help.

Here's what I got:

try 1:
Core was generated by `tapdisk'.
Program terminated with signal 11, Segmentation fault.
#0  0x00007fb42d2082d7 in pthread_cond_wait@@GLIBC_2.3.2 () from 
/lib/x86_64-linux-gnu/libpthread.so.0
(gdb) bt
#0  0x00007fb42d2082d7 in pthread_cond_wait@@GLIBC_2.3.2 () from 
/lib/x86_64-linux-gnu/libpthread.so.0
Cannot access memory at address 0x7fb42f081c38
(gdb) frame 0
#0  0x00007fb42d2082d7 in pthread_cond_wait@@GLIBC_2.3.2 () from 
/lib/x86_64-linux-gnu/libpthread.so.0
(gdb) list
77	}
78	
79	int
80	main(int argc, char *argv[])
81	{
82		char *control;
83		int c, err, nodaemon;
84		FILE *out;
85	
86		control  = NULL;
(gdb) info locals
No symbol table info available.

try 2:
Core was generated by `tapdisk'.
Program terminated with signal 11, Segmentation fault.
#0  0x00007fe05a721e6b in poll () from /lib/x86_64-linux-gnu/libc.so.6
(gdb) bt
#0  0x00007fe05a721e6b in poll () from /lib/x86_64-linux-gnu/libc.so.6
Cannot access memory at address 0x7fe05c2ba518
(gdb) frame 0
#0  0x00007fe05a721e6b in poll () from /lib/x86_64-linux-gnu/libc.so.6
(gdb) list
77	}
78	
79	int
80	main(int argc, char *argv[])
81	{
82		char *control;
83		int c, err, nodaemon;
84		FILE *out;
85	
86		control  = NULL;
(gdb) info locals
No symbol table info available.

Regards,

- Frederik