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qemu/include/qemu
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Marc-André Lureau 9e6bdef224 util: add qemu_write_pidfile() 
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>
2018-10-02 18:47:55 +02:00
..
acl.h Clean up ill-advised or unusual header guards 2016-07-12 16:20:46 +02:00
atomic.h util: add atomic64 2018-10-02 18:47:55 +02:00
base64.h Clean up ill-advised or unusual header guards 2016-07-12 16:20:46 +02:00
bcd.h Clean up decorations and whitespace around header guards 2016-07-12 16:20:46 +02:00
bitmap.h bitmap: provide to_le/from_le helpers 2017-09-22 14:11:25 +02:00
bitops.h vnc: replace hweight_long() with ctpopl() 2017-05-12 12:36:02 +02:00
bswap.h bswap: Add new stn_*_p() and ldn_*_p() memory access functions 2018-06-15 15:23:34 +01:00
buffer.h Clean up ill-advised or unusual header guards 2016-07-12 16:20:46 +02:00
compiler.h compiler: add a sizeof_field() macro 2018-06-27 13:01:40 +01:00
config-file.h Move include qemu/option.h from qemu-common.h to actual users 2018-02-09 13:52:16 +01:00
coroutine.h block: Add missing locking in bdrv_co_drain_bh_cb() 2018-09-25 15:50:15 +02:00
coroutine_int.h coroutine: avoid co_queue_wakeup recursion 2018-03-27 13:05:28 +01:00
cpuid.h util: Introduce include/qemu/cpuid.h 2017-07-24 12:42:55 +01:00
crc32c.h include/qemu/crc32c.h: Rename include guards to match filename 2014-02-26 17:20:07 +00:00
cutils.h cutils: Do not include "qemu/units.h" directly 2018-07-02 15:41:17 +02:00
drm.h util: promote qemu_egl_rendernode_open() to libqemuutil 2018-08-27 10:51:44 +02:00
envlist.h misc: move include files to include/qemu/ 2012-12-19 08:32:39 +01:00
error-report.h qemu-error: make use of {error, warn}_report_once_cond 2018-09-24 17:13:07 +02:00
event_notifier.h Revert "qemu: add a cleanup callback function to EventNotifier" 2018-01-24 19:20:19 +02:00
fifo8.h Clean up header guards that don't match their file name 2016-07-12 16:19:16 +02:00
fifo32.h hw: Clean up includes 2016-06-07 18:19:23 +03:00
fprintf-fn.h Clean up decorations and whitespace around header guards 2016-07-12 16:20:46 +02:00
futex.h futex: add missing header guards 2017-10-16 20:57:13 +03:00
hbitmap.h hbitmap: Add @advance param to hbitmap_iter_next() 2018-06-18 17:04:55 +02:00
help_option.h Clean up decorations and whitespace around header guards 2016-07-12 16:20:46 +02:00
host-utils.h pci/shpc: Move function to generic header file 2018-01-18 21:52:38 +02:00
id.h Clean up decorations and whitespace around header guards 2016-07-12 16:20:46 +02:00
int128.h tcg: Add atomic128 helpers 2016-10-26 08:29:01 -07:00
iov.h tests: Use real size for iov tests 2017-09-05 22:34:40 +02:00
iova-tree.h util: remove redundant include of glib.h and add osdep.h 2018-06-29 12:22:28 +01:00
jhash.h Jhash: add linux kernel jhashtable in qemu 2016-09-27 17:54:21 +08:00
job.h blockjob: Lie better in child_job_drained_poll() 2018-09-25 15:50:15 +02:00
lockable.h lockable: workaround GCC link issue with ASAN 2018-03-06 14:01:27 +01:00
log-for-trace.h log-for-trace.h: Split out parts of log.h used by trace.h 2018-03-12 11:10:20 +00:00
log.h tcg: Optionally log FPU state in TCG -d cpu logging 2018-05-15 14:58:44 +01:00
main-loop.h qsp: track BQL callers explicitly 2018-08-23 18:46:25 +02:00
memfd.h hostmem-memfd: add checks before adding hostmem-memfd & properties 2018-10-02 18:47:55 +02:00
mmap-alloc.h exec, kvm, target-ppc: Move getrampagesize() to common code 2017-03-03 11:30:59 +11:00
module.h audio: add module loading support 2018-03-12 11:18:26 +01:00
notify.h notify: add NotiferWithReturn so notifier list can abort 2013-06-28 09:20:26 +02:00
option.h opts: don't silently truncate long option values 2018-05-09 00:13:39 +02:00
option_int.h Clean up header guards that don't match their file name 2016-07-12 16:19:16 +02:00
osdep.h util: add qemu_write_pidfile() 2018-10-02 18:47:55 +02:00
path.h Clean up decorations and whitespace around header guards 2016-07-12 16:20:46 +02:00
pmem.h migration/ram: ensure write persistence on loading all data to PMEM. 2018-08-10 13:29:39 +03:00
processor.h Drop remaining bits of ia64 host support 2018-02-05 18:09:45 +01:00
qdist.h clean-includes: run it once more 2016-06-16 18:39:03 +02:00
qht.h qht: constify qht_statistics_init 2018-09-26 08:55:54 -07:00
qsp.h qsp: support call site coalescing 2018-08-23 18:46:25 +02:00
queue.h migration: hold the lock only if it is really needed 2018-08-22 12:36:18 +02:00
range.h range: Replace internal representation of Range 2016-07-04 16:49:33 +03:00
ratelimit.h ratelimit: don't align wait time with slices 2018-02-15 09:39:49 +00:00
rcu.h membarrier: introduce qemu/sys_membarrier.h 2018-03-12 16:12:47 +01:00
rcu_queue.h rcu_queue: add RCU QTAILQ 2018-08-23 18:46:25 +02:00
readline.h readline: add a free function 2018-01-16 14:54:50 +01:00
seqlock.h seqlock: add QemuLockable support 2018-08-23 18:46:25 +02:00
sockets.h sockets: move fd_is_socket() into common sockets code 2018-03-13 18:06:06 +00:00
stats64.h util: add stats64 module 2017-06-16 07:55:00 +08:00
sys_membarrier.h membarrier: add --enable-membarrier 2018-03-12 16:12:47 +01:00
systemd.h qemu-ga: obey LISTEN_PID when using systemd socket activation 2017-03-19 11:12:12 +01:00
thread-posix.h qsp: QEMU's Synchronization Profiler 2018-08-23 18:46:25 +02:00
thread-win32.h qsp: QEMU's Synchronization Profiler 2018-08-23 18:46:25 +02:00
thread.h qsp: hide indirect function calls from Coverity 2018-10-02 18:47:55 +02:00
throttle-options.h block: add throttle block filter driver 2017-09-06 10:12:02 +02:00
throttle.h Include less of the generated modular QAPI headers 2018-03-02 13:45:50 -06:00
timed-average.h include: Clean up includes 2016-02-23 12:43:05 +00:00
timer.h replay: save prior value of the host clock 2018-03-12 16:12:50 +01:00
typedefs.h typedefs: add QJSON 2018-06-15 14:40:56 +01:00
unicode.h json: Reject invalid UTF-8 sequences 2018-08-24 20:26:37 +02:00
units.h include: Add a lookup table of sizes 2018-10-01 12:51:12 +02:00
uri.h Remove unused function declarations 2016-09-15 15:32:22 +03:00
uuid.h util: add is_equal to UUID API 2017-12-20 22:01:24 +08:00
vfio-helpers.h util: Introduce vfio helpers 2018-02-08 09:22:03 +08:00
xattr.h include: Fix typos found by codespell 2017-01-24 23:26:52 +03:00