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[Qemu-devel] [PATCH v2 0/2] migration: fix deadlock
From: |
Denis V. Lunev |
Subject: |
[Qemu-devel] [PATCH v2 0/2] migration: fix deadlock |
Date: |
Fri, 25 Sep 2015 12:09:38 +0300 |
Release qemu global mutex before call synchronize_rcu().
synchronize_rcu() waiting for all readers to finish their critical
sections. There is at least one critical section in which we try
to get QGM (critical section is in address_space_rw() and
prepare_mmio_access() is trying to aquire QGM).
Both functions (migration_end() and migration_bitmap_extend())
are called from main thread which is holding QGM.
Thus there is a race condition that ends up with deadlock:
main thread working thread
Lock QGA |
| Call KVM_EXIT_IO handler
| |
| Open rcu reader's critical section
Migration cleanup bh |
| |
synchronize_rcu() is |
waiting for readers |
| prepare_mmio_access() is waiting for QGM
\ /
deadlock
Patches here are quick and dirty, compile-tested only to validate the
architectual approach.
Igor, Anna, can you pls start your tests with these patches instead of your
original one. Thank you.
Signed-off-by: Denis V. Lunev <address@hidden>
CC: Igor Redko <address@hidden>
CC: Anna Melekhova <address@hidden>
CC: Juan Quintela <address@hidden>
CC: Amit Shah <address@hidden>
Denis V. Lunev (2):
migration: bitmap_set is unnecessary as bitmap_new uses g_try_malloc0
migration: fix deadlock
migration/ram.c | 45 ++++++++++++++++++++++++++++-----------------
1 file changed, 28 insertions(+), 17 deletions(-)
--
2.1.4
- [Qemu-devel] [PATCH 1/1] migration: fix deadlock, Denis V. Lunev, 2015/09/24
- Re: [Qemu-devel] [PATCH 1/1] migration: fix deadlock, Wen Congyang, 2015/09/24
- Re: [Qemu-devel] [PATCH 1/1] migration: fix deadlock, Denis V. Lunev, 2015/09/25
- Re: [Qemu-devel] [PATCH 1/1] migration: fix deadlock, Wen Congyang, 2015/09/25
- [Qemu-devel] [PATCH v2 0/2] migration: fix deadlock,
Denis V. Lunev <=
- [Qemu-devel] [PATCH 1/2] migration: bitmap_set is unnecessary as bitmap_new uses g_try_malloc0, Denis V. Lunev, 2015/09/25
- Re: [Qemu-devel] [PATCH 1/2] migration: bitmap_set is unnecessary as bitmap_new uses g_try_malloc0, Wen Congyang, 2015/09/25
- Re: [Qemu-devel] [PATCH 1/2] migration: bitmap_set is unnecessary as bitmap_new uses g_try_malloc0, Denis V. Lunev, 2015/09/25
- Re: [Qemu-devel] [PATCH 1/2] migration: bitmap_set is unnecessary as bitmap_new uses g_try_malloc0, Wen Congyang, 2015/09/25
- Re: [Qemu-devel] [PATCH 1/2] migration: bitmap_set is unnecessary as bitmap_new uses g_try_malloc0, Denis V. Lunev, 2015/09/25
- [Qemu-devel] [PATCH 2/2] migration: fix deadlock, Denis V. Lunev, 2015/09/25
- Re: [Qemu-devel] [PATCH 2/2] migration: fix deadlock, Wen Congyang, 2015/09/25
- Re: [Qemu-devel] [PATCH v2 0/2] migration: fix deadlock, Wen Congyang, 2015/09/25
- Re: [Qemu-devel] [PATCH v2 0/2] migration: fix deadlock, Igor Redko, 2015/09/29
- Re: [Qemu-devel] [PATCH v2 0/2] migration: fix deadlock, Igor Redko, 2015/09/29