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migration: Move the yank unregister of channel_close out

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It's efficient, but hackish to call yank unregister calls in channel_close(),
especially it'll be hard to debug when qemu crashed with some yank function
leaked.

Remove that hack, but instead explicitly unregister yank functions at the
places where needed, they are:

  (on src)
  - migrate_fd_cleanup
  - postcopy_pause

  (on dst)
  - migration_incoming_state_destroy
  - postcopy_pause_incoming

Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20210722175841.938739-6-peterx@redhat.com>
Reviewed-by: Lukas Straub <lukasstraub2@web.de>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
This commit is contained in:
Peter Xu 2021-07-22 13:58:41 -04:00 • committed by Dr. David Alan Gilbert
parent c6ad5be7ae
commit 39675ffffb
5 changed files with 35 additions and 4 deletions
Download patch file Download diff file Expand all files Collapse all files

14
migration/migration.c
View file

@ -59,6 +59,7 @@
#include "multifd.h"
#include "qemu/yank.h"
#include "sysemu/cpus.h"
#include "yank_functions.h"
#define MAX_THROTTLE (128 << 20) /* Migration transfer speed throttling */
@ -273,6 +274,7 @@ void migration_incoming_state_destroy(void)
}
if (mis->from_src_file) {
migration_ioc_unregister_yank_from_file(mis->from_src_file);
qemu_fclose(mis->from_src_file);
mis->from_src_file = NULL;
}
@ -1811,6 +1813,7 @@ static void migrate_fd_cleanup(MigrationState *s)
* Close the file handle without the lock to make sure the
* critical section won't block for long.
*/
migration_ioc_unregister_yank_from_file(tmp);
qemu_fclose(tmp);
}
@ -3351,8 +3354,17 @@ static MigThrError postcopy_pause(MigrationState *s)
while (true) {
QEMUFile *file;
/* Current channel is possibly broken. Release it. */
/*
* Current channel is possibly broken. Release it. Note that this is
* guaranteed even without lock because to_dst_file should only be
* modified by the migration thread. That also guarantees that the
* unregister of yank is safe too without the lock. It should be safe
* even to be within the qemu_file_lock, but we didn't do that to avoid
* taking more mutex (yank_lock) within qemu_file_lock. TL;DR: we make
* the qemu_file_lock critical section as small as possible.
*/
assert(s->to_dst_file);
migration_ioc_unregister_yank_from_file(s->to_dst_file);
qemu_mutex_lock(&s->qemu_file_lock);
file = s->to_dst_file;
s->to_dst_file = NULL;