[Qemu-devel] Fwd: qemu drive mirror assert fault

[Paolo Bonzini]

John, Fam,

I got this report offlist.  This happens if a bit in the hbitmap is
cleared and the HBitmap has _not_ yet reached the bit.  See this comment
in include/qemu/hbitmap.h:

 * Resetting bits before the current
 * position of the iterator is also okay.  However, concurrent
 * resetting of bits can lead to unexpected behavior if the iterator
 * has not yet reached those bits.

Can you please take a look?

Thanks,

Paolo

-------- Forwarded Message --------
Subject:        qemu drive mirror assert fault
Date:   Wed, 29 Apr 2015 10:50:28 +0800
From:   wangxiaolong <address@hidden>
To:     pbonzini <address@hidden>

hello,

I used drive mirror to do live migration, and I run into such an assert
fault:

(gdb) bt

#0  0x00007fd2c6e678a5 in raise (sig=6) at
../nptl/sysdeps/unix/sysv/linux/raise.c:64

#1  0x00007fd2c6e69085 in abort () at abort.c:92

#2  0x00007fd2c6e60a1e in __assert_fail_base (fmt=<value optimized out>,
assertion=0x7fd2ca215aa0 "cur", file=0x7fd2ca215a78 "util/hbitmap.c",
line=<value optimized out>,

    function=<value optimized out>) at assert.c:96

#3  0x00007fd2c6e60ae0 in __assert_fail (assertion=0x7fd2ca215aa0 "cur",
file=0x7fd2ca215a78 "util/hbitmap.c", line=129, function=0x7fd2ca215bf0
"hbitmap_iter_skip_words")

    at assert.c:105

#4  0x00007fd2ca1b3bb8 in hbitmap_iter_skip_words (hbi=<value optimized
out>) at util/hbitmap.c:129

#5  0x00007fd2c9f8f8e0 in hbitmap_iter_next (opaque=0x7fd2cc59c730) at
/usr/src/debug/qemu-kvm-1.5.3/include/qemu/hbitmap.h:166

#6  mirror_iteration (opaque=0x7fd2cc59c730) at block/mirror.c:163

#7  mirror_run (opaque=0x7fd2cc59c730) at block/mirror.c:407

#8  0x00007fd2c9fc45bb in coroutine_trampoline (i0=<value optimized
out>, i1=<value optimized out>) at coroutine-ucontext.c:118

#9  0x00007fd2c6e78b70 in ?? () from /lib64/libc-2.12.so

#10 0x00007fff53eede80 in ?? ()

#11 0x0000000000000000 in ?? ()


and I just can’t figure out what is the cause of this situation,
could you help me figure it out, thanks!