Patch 1 fixes a possible race that migration thread can accidentally skip join() of rp_thread even if the return thread is enabled. Patch 1 is suspected to also be the root cause of the recent hard-to-reproduce migration-test failure here reported by PMM:
https://lore.kernel.org/qemu-devel/YPamXAHwan%2FPPXLf@work-vm/ I didn't reproduce it myself; but after co-debugged with Dave it's suspected that the race of rp_thread could be the cause. It's not exposed before because yank is soo strict on releasing instances, while we're not that strict before, and didn't join() on rp_thread wasn't so dangerous after all when migration succeeded before. Patch 2 fixes another theoretical race on accessing from_dst_file spotted by Dave. I don't think there's known issues with it, but may still worth fixing. Patch 3 should be a cleanup on yank that I think would be nice to have. Patch 4-5 are further cleanups to remove the ref==1 check in channel_close(), finally, as I always thought that's a bit hackish. So I used explicit unregister of the yank function at necessary places to replace that ref==1 one. I still think having patch 3-5 altogether would be great, however I think patch 1 should still be the most important to be reviewed. Also it would be great to know whether patch 1 could fix the known yank crash. Please review, thanks. Peter Xu (5): migration: Fix missing join() of rp_thread migration: Shutdown src in await_return_path_close_on_source() migration: Introduce migration_ioc_[un]register_yank() migration: Teach QEMUFile to be QIOChannel-aware migration: Move the yank unregister of channel_close out migration/channel.c | 15 ++----------- migration/migration.c | 18 +++++++++++---- migration/migration.h | 7 ++++++ migration/multifd.c | 8 ++----- migration/qemu-file-channel.c | 11 ++------- migration/qemu-file.c | 17 +++++++++++++- migration/qemu-file.h | 4 +++- migration/ram.c | 2 +- migration/savevm.c | 11 +++++++-- migration/yank_functions.c | 42 +++++++++++++++++++++++++++++++++++ migration/yank_functions.h | 3 +++ 11 files changed, 101 insertions(+), 37 deletions(-) -- 2.31.1
