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9e6bdef224
There are variants of qemu_create_pidfile() in qemu-pr-helper and
qemu-ga. Let's have a common implementation in libqemuutil.
The code is initially based from pr-helper write_pidfile(), with
various improvements and suggestions from Daniel Berrangé:
QEMU will leave the pidfile existing on disk when it exits which
initially made me think it avoids the deletion race. The app
managing QEMU, however, may well delete the pidfile after it has
seen QEMU exit, and even if the app locks the pidfile before
deleting it, there is still a race.
eg consider the following sequence
QEMU 1 libvirtd QEMU 2
1. lock(pidfile)
2. exit()
3. open(pidfile)
4. lock(pidfile)
5. open(pidfile)
6. unlink(pidfile)
7. close(pidfile)
8. lock(pidfile)
IOW, at step 8 the new QEMU has successfully acquired the lock, but
the pidfile no longer exists on disk because it was deleted after
the original QEMU exited.
While we could just say no external app should ever delete the
pidfile, I don't think that is satisfactory as people don't read
docs, and admins don't like stale pidfiles being left around on
disk.
To make this robust, I think we might want to copy libvirt's
approach to pidfile acquisition which runs in a loop and checks that
the file on disk /after/ acquiring the lock matches the file that
was locked. Then we could in fact safely let QEMU delete its own
pidfiles on clean exit..
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20180831145314.14736-2-marcandre.lureau@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
99 lines
3 KiB
C
99 lines
3 KiB
C
/*
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* os-win32.c
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*
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* Copyright (c) 2003-2008 Fabrice Bellard
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* Copyright (c) 2010 Red Hat, Inc.
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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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#include "qemu/osdep.h"
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#include <windows.h>
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#include <mmsystem.h>
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#include "sysemu/sysemu.h"
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#include "qemu-options.h"
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/***********************************************************/
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/* Functions missing in mingw */
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int setenv(const char *name, const char *value, int overwrite)
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{
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int result = 0;
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if (overwrite || !getenv(name)) {
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size_t length = strlen(name) + strlen(value) + 2;
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char *string = g_malloc(length);
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snprintf(string, length, "%s=%s", name, value);
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result = putenv(string);
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/* Windows takes a copy and does not continue to use our string.
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* Therefore it can be safely freed on this platform. POSIX code
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* typically has to leak the string because according to the spec it
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* becomes part of the environment.
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*/
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g_free(string);
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}
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return result;
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}
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static BOOL WINAPI qemu_ctrl_handler(DWORD type)
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{
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qemu_system_shutdown_request(SHUTDOWN_CAUSE_HOST_SIGNAL);
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/* Windows 7 kills application when the function returns.
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Sleep here to give QEMU a try for closing.
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Sleep period is 10000ms because Windows kills the program
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after 10 seconds anyway. */
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Sleep(10000);
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return TRUE;
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}
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static TIMECAPS mm_tc;
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static void os_undo_timer_resolution(void)
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{
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timeEndPeriod(mm_tc.wPeriodMin);
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}
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void os_setup_early_signal_handling(void)
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{
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SetConsoleCtrlHandler(qemu_ctrl_handler, TRUE);
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timeGetDevCaps(&mm_tc, sizeof(mm_tc));
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timeBeginPeriod(mm_tc.wPeriodMin);
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atexit(os_undo_timer_resolution);
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}
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/* Look for support files in the same directory as the executable. */
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char *os_find_datadir(void)
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{
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return qemu_get_exec_dir();
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}
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void os_set_line_buffering(void)
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{
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setbuf(stdout, NULL);
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setbuf(stderr, NULL);
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}
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/*
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* Parse OS specific command line options.
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* return 0 if option handled, -1 otherwise
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*/
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int os_parse_cmd_args(int index, const char *optarg)
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{
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return -1;
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}
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