d6b9de8f9e
When starting a dummy QEMU process with virsh version, monitor_init_qmp() enables IOThread monitoring of the QMP fd by default. However, a race condition exists during the initialization phase: the IOThread only removes the main thread's fd watch when it reaches qio_net_listener_set_client_func_full(), which may be delayed under high system load. This creates a window between monitor_qmp_setup_handlers_bh() and qio_net_listener_set_client_func_full() where both the main thread and IOThread are simultaneously monitoring the same fd and processing events. This race can cause either the main thread or the IOThread to hang and become unresponsive. Fix this by proactively cleaning up the listener's IO sources in monitor_init_qmp() before the IOThread initializes QMP monitoring, ensuring exclusive fd ownership and eliminating the race condition. Signed-off-by: Jie Song <songjie_yewu@cmss.chinamobile.com> Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com> Message-ID: <20251125140706.114197-1-mail@jiesong.me> (cherry picked from commit e714f1a3d4d1e66b9a3ff4be1ff999c32bbef29e) Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
48 lines
1.8 KiB
C
48 lines
1.8 KiB
C
/*
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* QEMU System Emulator
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*
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* Copyright (c) 2003-2008 Fabrice Bellard
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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#ifndef CHAR_IO_H
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#define CHAR_IO_H
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#include "io/channel.h"
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#include "chardev/char.h"
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#include "qemu/main-loop.h"
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/* Can only be used for read */
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GSource *io_add_watch_poll(Chardev *chr,
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QIOChannel *ioc,
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IOCanReadHandler *fd_can_read,
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QIOChannelFunc fd_read,
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gpointer user_data,
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GMainContext *context);
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void remove_fd_in_watch(Chardev *chr);
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int io_channel_send(QIOChannel *ioc, const void *buf, size_t len);
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int io_channel_send_full(QIOChannel *ioc, const void *buf, size_t len,
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int *fds, size_t nfds);
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void remove_listener_fd_in_watch(Chardev *chr);
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#endif /* CHAR_IO_H */
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