Stack from qemu_fill_buffer to qio_channel_socket_readv
#0 qio_channel_socket_readv (ioc=<optimized out>, iov=<optimized out>,
niov=<optimized out>, fds=0x0, nfds=0x0, errp=0x0)
at ./io/channel-socket.c:477
#1 0x0000001486ec97e2 in qio_channel_read (ioc=ioc@entry=0x148a73a6c0,
buf=buf@entry=\060\nLw", buflen=buflen@entry=28728, errp=errp@entry=0x0) at
./io/channel.c:112
#2 0x0000001486e005ec in channel_get_buffer (opaque=<optimized out>,
buf=0x1489844c00 "\060\nLw", pos=<optimized out>, size=28728) at
./migration/qemu-file-channel.c:80
#3 0x0000001486dff095 in qemu_fill_buffer (f=f@entry=0x1489843c00) at
./migration/qemu-file.c:293
I checked that sioc->fd, &msg, sflags) is in fact the socket.
With e.g. with this fd being 27
tcp ESTAB 1405050 0 ::ffff:10.22.69.30:49152
::ffff:10.22.69.157:49804
users:(("qemu-system-x86",pid=29273,fd=27)) ino:3345152 sk:30 <->
skmem:(r1420644,rb1495660,t0,tb332800,f668,w0,o0,bl0,d14) ts sack
cubic wscale:7,7 rto:200 rtt:0.04/0.02 ato:80 mss:8948 cwnd:10
bytes_received:1981460 segs_out:37 segs_in:247 data_segs_in:231 send
17896.0Mbps lastsnd:254728 lastrcv:250372 lastack:250372 rcv_rtt:0.205
rcv_space:115461 minrtt:0.04
I need to break on the fail of that recvmsg in qio_channel_socket_readv
# the following does not work due to optimization the ret value is only around
later
b io/channel-socket.c:478 if ret < 0
But catching it "inside" the if works
b io/channel-socket.c:479
Take the following with a grain of salt, this is very threaded and noisy to
debug.
Once I hit it the recmsg returned "-1", that was on f->pos = 311641887
But at the same time I could confirm (via ss) that the socket itself is still
open on source and target of the migration.
-1 is EAGAIN and returns QIO_CHANNEL_ERR_BLOCK
That seems to arrive in nbd_rwv nbd/common.c:44).
And led to "qio_channel_yield"
There are a few corouting switches in between so I hope I'm not loosing
anything.
But that first ret<0 actually worked, it seems the yield and retry got it
working.
I got back to qemu_fill_buffer iterating further after this.
This hit ret<0 in qio_channel_socket_readv again at f->pos 311641887.
This time on returning the QIO_CHANNEL_ERR_BLOCK it returned to
"./migration/qemu-file-channel.c:81".
That was interesting as it is different than before.
After this it seemed to become a death spiral - recmsg returned -1 every time
(still on the same offset).
It passed back through the nbd_rwv which called qio_channel_yield for multiple
times.
Then it continued and later on on 321998304 is the last I saw.
It did no more pass b io/channel-socket.c:479 at all, but then led to the exit.
Hmm, I might have lost myself on the coroutine switches - but it is odd at
least.
Trying to redo less interactive and with a bit more prep ...
Maybe the results are more reliable then ...
Getting back with more later ...
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https://bugs.launchpad.net/bugs/1711602
Title:
--copy-storage-all failing with qemu 2.10
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