These are the next part in the unlocked address space dispatch work.
At the end of this series, address space dispatch runs under an RCU
critical section (RCU is hopefully well documented in patch 8).
It becomes then possible to add unlocked variants of address_space_rw.
Compared to Liu Ping Fan's approach posted last year, the path I followed
is more long-winded but requires much less changes in device models that
choose to adopt lockless MMIO dispatching. This is nice, because it
produces an API that is easier to use.
In addition, I decided to sidestep complicated locking discussions by
using RCU. RCU can bulk-protect the read side of all data structures
while remaining extremely light-weight. The write side needs its own
lock, but in many cases it can simply be the BQL (very useful for things
that perform updates in callbacks!).
Patches 1-3 add reference counting to FlatView, which is independent
from the other patches but a necessary prerequisite to protect
as->current_map with RCU.
Patches 4-17 implement RCU and update existing threads to be RCU-friendly
(again, more information is in docs/rcu.txt) whenever necessary.
A lot of the code here comes from the URCU library.
Patches 18-30 do the rest of the work, using fresh copies of the dispatch
data structures on every update. Several patches in this series are
based on Liu Ping Fan's work, which I made more fine-grained.
The diffstat looks daunting; however, note that ~50% of the new lines
are documentation and test cases. Available from branch rcu of my
github repository.
I don't plan to send a pull request for this series anytime soon,
but reviews and testing are welcome.
Paolo
Liu Ping Fan (1):
exec: change well-known physical sections to macros
Paolo Bonzini (29):
memory: access FlatView from a local variable
memory: use a new FlatView pointer on every topology update
memory: add reference counting to FlatView
add a header file for atomic operations
exec: do not use qemu/tls.h
qemu-thread: add TLS wrappers
qemu-thread: add QemuEvent
rcu: add rcu library
qemu-thread: register threads with RCU
rcu: add call_rcu
rcu: add rcutorture
rcu: allow nested calls to rcu_thread_offline/rcu_thread_online
qemu-thread: report RCU quiescent states
event loop: report RCU quiescent states
cpus: report RCU quiescent states
block: report RCU quiescent states
migration: report RCU quiescent states
memory: protect current_map by RCU
memory: avoid ref/unref in memory_region_find
exec: separate current memory map from the one being built
memory: move MemoryListener declaration earlier
exec: move listener from AddressSpaceDispatch to AddressSpace
exec: separate current radix tree from the one being built
exec: put memory map in AddressSpaceDispatch
exec: remove cur_map
exec: change some APIs to take AddressSpaceDispatch
exec: change iotlb APIs to take AddressSpaceDispatch
exec: add a reference to the region returned by
address_space_translate
exec: put address space dispatch under RCU critical section
aio-posix.c | 8 +
aio-win32.c | 11 +-
block/raw-posix.c | 3 +
block/raw-win32.c | 3 +
configure | 21 +++
cpus.c | 3 +
cputlb.c | 9 +-
docs/atomics.txt | 345 ++++++++++++++++++++++++++++++++++
docs/rcu.txt | 440 ++++++++++++++++++++++++++++++++++++++++++++
exec.c | 244 ++++++++++++++++--------
hw/9pfs/virtio-9p-synth.c | 1 +
hw/display/qxl.c | 3 +-
hw/ppc/spapr_iommu.c | 10 +-
hw/virtio/vhost.c | 9 +-
include/exec/cpu-all.h | 14 +-
include/exec/cputlb.h | 9 +-
include/exec/memory.h | 77 ++++----
include/qemu/atomic.h | 190 +++++++++++++++----
include/qemu/queue.h | 13 ++
include/qemu/rcu-pointer.h | 110 +++++++++++
include/qemu/rcu.h | 180 ++++++++++++++++++
include/qemu/thread-posix.h | 8 +
include/qemu/thread-win32.h | 4 +
include/qemu/thread.h | 10 +-
include/qemu/tls.h | 125 +++++++++++--
kvm-all.c | 3 +
libcacard/Makefile | 3 +-
main-loop.c | 6 +
memory.c | 127 +++++++++----
migration.c | 5 +-
tests/Makefile | 10 +-
tests/rcutorture.c | 439 +++++++++++++++++++++++++++++++++++++++++++
tests/test-thread-pool.c | 8 +-
tests/test-tls.c | 87 +++++++++
util/Makefile.objs | 1 +
util/qemu-thread-posix.c | 174 +++++++++++++++++-
util/qemu-thread-win32.c | 61 +++++-
util/rcu.c | 312 +++++++++++++++++++++++++++++++
38 files changed, 2857 insertions(+), 229 deletions(-)
create mode 100644 docs/atomics.txt
create mode 100644 docs/rcu.txt
create mode 100644 include/qemu/rcu-pointer.h
create mode 100644 include/qemu/rcu.h
create mode 100644 tests/rcutorture.c
create mode 100644 tests/test-tls.c
create mode 100644 util/rcu.c
--
1.8.1.4
