Re: [Qemu-devel] [PATCH v2] gdb command: qemu handlers

[Stefan Hajnoczi <stefanha@redhat.com>]

On Tue, Oct 27, 2015 at 01:09:45PM +0000, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> 
> 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>
> 
> 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  ()
> 
>   ----
> ---
>  scripts/qemu-gdb.py    |  3 ++-
>  scripts/qemugdb/aio.py | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 60 insertions(+), 1 deletion(-)
>  create mode 100644 scripts/qemugdb/aio.py

Thanks, applied to my block tree:
https://github.com/stefanha/qemu/commits/block

Stefan