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A new gdb commands are added:
qemu handlers
That dumps an AioContext list (by default qemu_aio_context)
possibly including a backtrace for cases it knows about
(with the verbose option). Intended to help find why something
is hanging waiting for IO.
Use 'qemu handlers --verbose iohandler_ctx' to find out why
your incoming migration is stuck.
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-id: 1445951385-11924-1-git-send-email-dgilbert@redhat.com
V2:
Merge into one command with optional handlers arg, and only do
backtrace in verbose mode
(gdb) qemu handlers
----
{pfd = {fd = 6, events = 25, revents = 0}, io_read = 0x55869656ffd0
<event_notifier_dummy_cb>, io_write = 0x0, deleted = 0, opaque =
0x558698c4ce08, node = {le_next = 0x0, le_prev = 0x558698c4cdc0}}
(gdb) qemu handlers iohandler_ctx
----
{pfd = {fd = 9, events = 25, revents = 0}, io_read = 0x558696581380
<fd_coroutine_enter>, io_write = 0x0, deleted = 0, opaque =
0x558698dc99d0, node = {le_next = 0x558698c4cca0, le_prev =
0x558698c4c1d0}}
----
{pfd = {fd = 4, events = 25, revents = 0}, io_read = 0x55869657b330
<sigfd_handler>, io_write = 0x0, deleted = 0, opaque = 0x4, node =
{le_next = 0x558698c4c260, le_prev = 0x558699f72508}}
----
{pfd = {fd = 5, events = 25, revents = 0}, io_read = 0x55869656ffd0
<event_notifier_dummy_cb>, io_write = 0x0, deleted = 0, opaque =
0x558698c4c218, node = {le_next = 0x0, le_prev = 0x558698c4ccc8}}
----
(gdb) qemu handlers --verbose iohandler_ctx
----
{pfd = {fd = 9, events = 25, revents = 0}, io_read = 0x558696581380
<fd_coroutine_enter>, io_write = 0x0, deleted = 0, opaque =
0x558698dc99d0, node = {le_next = 0x558698c4cca0, le_prev =
0x558698c4c1d0}}
#0 0x0000558696581820 in qemu_coroutine_switch
(from_=from_@entry=0x558698cb3cf0, to_=to_@entry=0x7f421c37eac8,
action=action@entry=COROUTINE_YIELD) at
/home/dgilbert/git/qemu/coroutine-ucontext.c:177
#1 0x0000558696580c00 in qemu_coroutine_yield () at
/home/dgilbert/git/qemu/qemu-coroutine.c:145
#2 0x00005586965814f5 in yield_until_fd_readable (fd=9) at
/home/dgilbert/git/qemu/qemu-coroutine-io.c:90
#3 0x0000558696523937 in socket_get_buffer (opaque=0x55869a3dc620,
buf=0x558698c505a0 "", pos=<optimized out>, size=32768) at
/home/dgilbert/git/qemu/migration/qemu-file-unix.c:101
#4 0x0000558696521fac in qemu_fill_buffer (f=0x558698c50570) at
/home/dgilbert/git/qemu/migration/qemu-file.c:227
#5 0x0000558696522989 in qemu_peek_byte (f=0x558698c50570, offset=0)
at /home/dgilbert/git/qemu/migration/qemu-file.c:507
#6 0x0000558696522bf4 in qemu_get_be32 (f=0x558698c50570) at
/home/dgilbert/git/qemu/migration/qemu-file.c:520
#7 0x0000558696522bf4 in qemu_get_be32 (f=f@entry=0x558698c50570)
at /home/dgilbert/git/qemu/migration/qemu-file.c:604
#8 0x0000558696347e5c in qemu_loadvm_state (f=f@entry=0x558698c50570)
at /home/dgilbert/git/qemu/migration/savevm.c:1821
#9 0x000055869651de8c in process_incoming_migration_co
(opaque=0x558698c50570)
at /home/dgilbert/git/qemu/migration/migration.c:336
#10 0x000055869658188a in coroutine_trampoline (i0=<optimized out>,
i1=<optimized out>)
at /home/dgilbert/git/qemu/coroutine-ucontext.c:80
#11 0x00007f420f05df10 in __start_context () at /lib64/libc.so.6
#12 0x00007ffc40815f50 in ()
#13 0x0000000000000000 in ()
----
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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The 'qemu coroutine <coroutine-address>' GDB command prints the
backtrace for a CoroutineUContext. This is useful for peeking inside
yielded coroutines that are waiting for file descriptor events, timers,
etc.
For example:
$ gdb tests/test-coroutine
(gdb) b test_yield
(gdb) r
(gdb) b qemu_coroutine_enter
(gdb) c
(gdb) c
Continuing.
Breakpoint 2, qemu_coroutine_enter (co=0x555555c66520, opaque=0x0) at qemu-coroutine.c:103
103 {
(gdb) source scripts/qemu-gdb.py
(gdb) qemu coroutine 0x555555c66520
#0 0x000055555557a740 in qemu_coroutine_switch (from_=<optimized out>, to_=0x7ffff7f90a70, action=COROUTINE_YIELD) at coroutine-ucontext.c:177
#1 0x0000555555566af9 in yield_5_times (opaque=0x7fffffffdbb7) at tests/test-coroutine.c:107
#2 0x000055555557a7aa in coroutine_trampoline (i0=<optimized out>, i1=<optimized out>) at coroutine-ucontext.c:80
#3 0x00007ffff08de000 in __start_context () at /lib64/libc.so.6
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 1427409754-8556-1-git-send-email-stefanha@redhat.com
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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