Re: Migration issues in qemu.git

[Avi Kivity <avi@redhat.com>]

  On 08/02/2010 04:12 PM, Alex Williamson wrote:
> On Mon, 2010-08-02 at 12:42 +0300, Avi Kivity wrote:
>> On 08/02/2010 12:06 PM, Avi Kivity wrote:
>>>   I'm hitting some migration issues merging qemu.git into qemu-kvm.git:
>>>
>>> 1. Crash in mig_cancel test:
>>>
>>> (gdb) bt
>>> #0  0x0000003a91c83dbb in memcpy () from /lib64/libc.so.6
>>> #1  0x000000000049c2ff in qemu_get_buffer (f=0x302d870, buf=<value
>>> optimized out>, size1=4096) at /usr/include/bits/string3.h:52
>>> #2  0x0000000000409464 in ram_load (f=0x302d870, opaque=<value
>>> optimized out>, version_id=4) at
>>> /build/home/tlv/akivity/qemu-kvm/arch_init.c:407
>>> #3  0x000000000049cb4c in qemu_loadvm_state (f=0x302d870) at
>>> savevm.c:1708
>>> #4  0x0000000000494169 in process_incoming_migration (f=<value
>>> optimized out>) at migration.c:63
>>> #5  0x0000000000494517 in tcp_accept_incoming_migration (opaque=<value
>>> optimized out>) at migration-tcp.c:163
>>> #6  0x000000000041b67e in main_loop_wait (nonblocking=<value optimized
>>> out>) at /build/home/tlv/akivity/qemu-kvm/vl.c:1300
>>> #7  0x00000000004314e7 in kvm_main_loop () at
>>> /build/home/tlv/akivity/qemu-kvm/qemu-kvm.c:1710
>>> #8  0x000000000041c67f in main_loop (argc=<value optimized out>,
>>> argv=<value optimized out>, envp=<value optimized out>)
>>>      at /build/home/tlv/akivity/qemu-kvm/vl.c:1340
>>> #9  main (argc=<value optimized out>, argv=<value optimized out>,
>>> envp=<value optimized out>) at /build/home/tlv/akivity/qemu-kvm/vl.c:3069
>>>
>>> This is on the incoming side so the test completes successfully, only
>>> leaving a core dump to fill my disks.
>>
>> This appears to be
>>
>>> static inline void *host_from_stream_offset(QEMUFile *f,
>>>                                              ram_addr_t offset,
>>>                                              int flags)
>>> {
>>>      static RAMBlock *block = NULL;
>>>      char id[256];
>>>      uint8_t len;
>>>
>>>      if (flags&  RAM_SAVE_FLAG_CONTINUE) {
>>>          if (!block) {
>>>              fprintf(stderr, "Ack, bad migration stream!\n");
>>>              return NULL;
>>>          }
>>>
>>>          return block->host + offset;
>>>      }
>> with block == NULL, if my gdb-fu got a static variable in an inlined
>> function examined correctly.
> If block == NULL, are you getting the fprintf?

Looked in qemu logs, but didn't see it.  Maybe I missed it in the noise, 
or maybe autotest saw SIGCHLD and closed the logging channel.

>> I don't see any special reason for block to be NULL on a cancelled
>> migration.  Though perhaps the incoming stream was terminated without us
>> noticing, and we're migrating from some random buffer and confusing the
>> code?
> Yeah, I don't understand that either, block == NULL should only be an
> initial state, once we've seen a block it shouldn't happen.  Does this
> patch solve anything:
>
> http://lists.nongnu.org/archive/html/qemu-devel/2010-07/msg01114.html
>
> I could see this fixing it if the migration was re-attempted after the
> cancel.

I'll try it manually and see.

-- 
error compiling committee.c: too many arguments to function