Hi On Thu, Aug 26, 2021 at 10:58 PM Peter Xu <pet...@redhat.com> wrote:
> Both dump-guest-memory and live migration caches vm state at the beginning. > Either of them entering the other one will cause race on the vm state, and > even > more severe on that (please refer to the crash report in the bug link). > > Let's block live migration in dump-guest-memory, and that'll also block > dump-guest-memory if it detected that we're during a live migration. > > Side note: migrate_del_blocker() can be called even if the blocker is not > inserted yet, so it's safe to unconditionally delete that blocker in > dump_cleanup (g_slist_remove allows no-entry-found case). > > Suggested-by: Dr. David Alan Gilbert <dgilb...@redhat.com> > Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1996609 > Signed-off-by: Peter Xu <pet...@redhat.com> > --- > dump/dump.c | 24 +++++++++++++++++++----- > 1 file changed, 19 insertions(+), 5 deletions(-) > > diff --git a/dump/dump.c b/dump/dump.c > index ab625909f3..9c1c1fb738 100644 > --- a/dump/dump.c > +++ b/dump/dump.c > @@ -29,6 +29,7 @@ > #include "qemu/error-report.h" > #include "qemu/main-loop.h" > #include "hw/misc/vmcoreinfo.h" > +#include "migration/blocker.h" > > #ifdef TARGET_X86_64 > #include "win_dump.h" > @@ -47,6 +48,8 @@ > > #define MAX_GUEST_NOTE_SIZE (1 << 20) /* 1MB should be enough */ > > +static Error *dump_migration_blocker; > + > #define ELF_NOTE_SIZE(hdr_size, name_size, desc_size) \ > ((DIV_ROUND_UP((hdr_size), 4) + \ > DIV_ROUND_UP((name_size), 4) + \ > @@ -101,6 +104,7 @@ static int dump_cleanup(DumpState *s) > qemu_mutex_unlock_iothread(); > } > } > + migrate_del_blocker(dump_migration_blocker); > > return 0; > } > @@ -1927,11 +1931,6 @@ void qmp_dump_guest_memory(bool paging, const char > *file, > Error *local_err = NULL; > bool detach_p = false; > > - if (runstate_check(RUN_STATE_INMIGRATE)) { > - error_setg(errp, "Dump not allowed during incoming migration."); > - return; > - } > - > /* if there is a dump in background, we should wait until the dump > * finished */ > if (dump_in_progress()) { > @@ -2005,6 +2004,21 @@ void qmp_dump_guest_memory(bool paging, const char > *file, > return; > } > > + if (!dump_migration_blocker) { > + error_setg(&dump_migration_blocker, > + "Live migration disabled: dump-guest-memory in > progress"); > + } > + > + /* > + * Allows even for -only-migratable, but forbid migration during the > + * process of dump guest memory. > + */ > + if (migrate_add_blocker_internal(dump_migration_blocker, errp)) { > + /* Remember to release the fd before passing it over to dump > state */ > + close(fd); > + return; > + } > I would move it earlier. Why not leave it at the beginning of the function as it was? Then dump_in_progress() is probably redundant too. + > s = &dump_state_global; > dump_state_prepare(s); > > -- > 2.31.1 > >
