From c900ef86c5e30e1adec0f79350edc3f30ebee285 Mon Sep 17 00:00:00 2001 From: "Dr. David Alan Gilbert" Date: Tue, 27 Oct 2015 13:09:45 +0000 Subject: gdb command: qemu handlers 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 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 , 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 , io_write = 0x0, deleted = 0, opaque = 0x558698dc99d0, node = {le_next = 0x558698c4cca0, le_prev = 0x558698c4c1d0}} ---- {pfd = {fd = 4, events = 25, revents = 0}, io_read = 0x55869657b330 , io_write = 0x0, deleted = 0, opaque = 0x4, node = {le_next = 0x558698c4c260, le_prev = 0x558699f72508}} ---- {pfd = {fd = 5, events = 25, revents = 0}, io_read = 0x55869656ffd0 , 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 , 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=, 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=, i1=) 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 --- scripts/qemugdb/aio.py | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 58 insertions(+) create mode 100644 scripts/qemugdb/aio.py (limited to 'scripts/qemugdb') diff --git a/scripts/qemugdb/aio.py b/scripts/qemugdb/aio.py new file mode 100644 index 0000000000..2ba00c4444 --- /dev/null +++ b/scripts/qemugdb/aio.py @@ -0,0 +1,58 @@ +#!/usr/bin/python + +# GDB debugging support: aio/iohandler debug +# +# Copyright (c) 2015 Red Hat, Inc. +# +# Author: Dr. David Alan Gilbert +# +# This work is licensed under the terms of the GNU GPL, version 2 or +# later. See the COPYING file in the top-level directory. +# + +import gdb +from qemugdb import coroutine + +def isnull(ptr): + return ptr == gdb.Value(0).cast(ptr.type) + +def dump_aiocontext(context, verbose): + '''Display a dump and backtrace for an aiocontext''' + cur = context['aio_handlers']['lh_first'] + # Get pointers to functions we're going to process specially + sym_fd_coroutine_enter = gdb.parse_and_eval('fd_coroutine_enter') + + while not isnull(cur): + entry = cur.dereference() + gdb.write('----\n%s\n' % entry) + if verbose and cur['io_read'] == sym_fd_coroutine_enter: + coptr = (cur['opaque'].cast(gdb.lookup_type('FDYieldUntilData').pointer()))['co'] + coptr = coptr.cast(gdb.lookup_type('CoroutineUContext').pointer()) + coroutine.bt_jmpbuf(coptr['env']['__jmpbuf']) + cur = cur['node']['le_next']; + + gdb.write('----\n') + +class HandlersCommand(gdb.Command): + '''Display aio handlers''' + def __init__(self): + gdb.Command.__init__(self, 'qemu handlers', gdb.COMMAND_DATA, + gdb.COMPLETE_NONE) + + def invoke(self, arg, from_tty): + verbose = False + argv = gdb.string_to_argv(arg) + + if len(argv) > 0 and argv[0] == '--verbose': + verbose = True + argv.pop(0) + + if len(argv) > 1: + gdb.write('usage: qemu handlers [--verbose] [handler]\n') + return + + if len(argv) == 1: + handlers_name = argv[0] + else: + handlers_name = 'qemu_aio_context' + dump_aiocontext(gdb.parse_and_eval(handlers_name), verbose) -- cgit v1.2.1