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[PATCH v2 0/5] migrations: Fix potential rare race of migration-test aft
From: |
Peter Xu |
Subject: |
[PATCH v2 0/5] migrations: Fix potential rare race of migration-test after yank |
Date: |
Wed, 21 Jul 2021 15:34:04 -0400 |
v2:
- Pick r-b for Dave on patch 1/3
- Move migration_file_get_ioc() from patch 5 to patch 4, meanwhile rename it to
qemu_file_get_ioc(). [Dave]
- Patch 2 "migration: Shutdown src in await_return_path_close_on_source()" is
replaced by patch "migration: Make from_dst_file accesses thread-safe" [Dave]
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: Make from_dst_file accesses thread-safe
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 | 41 +++++++++++++++++++++++++++-------
migration/migration.h | 15 ++++++++++---
migration/multifd.c | 8 ++-----
migration/qemu-file-channel.c | 11 ++-------
migration/qemu-file.c | 17 +++++++++++++-
migration/qemu-file.h | 4 +++-
migration/ram.c | 3 ++-
migration/savevm.c | 11 +++++++--
migration/yank_functions.c | 42 +++++++++++++++++++++++++++++++++++
migration/yank_functions.h | 3 +++
11 files changed, 126 insertions(+), 44 deletions(-)
--
2.31.1
- [PATCH v2 0/5] migrations: Fix potential rare race of migration-test after yank,
Peter Xu <=
- [PATCH v2 1/5] migration: Fix missing join() of rp_thread, Peter Xu, 2021/07/21
- [PATCH v2 2/5] migration: Make from_dst_file accesses thread-safe, Peter Xu, 2021/07/21
- [PATCH v2 3/5] migration: Introduce migration_ioc_[un]register_yank(), Peter Xu, 2021/07/21
- [PATCH v2 4/5] migration: Teach QEMUFile to be QIOChannel-aware, Peter Xu, 2021/07/21
- [PATCH v2 5/5] migration: Move the yank unregister of channel_close out, Peter Xu, 2021/07/21