| Message ID | 20200407140746.8041-1-pbonzini@redhat.com |
|---|---|
| Headers | show |
| Series | async: fix hangs on weakly-ordered architectures | expand |
On 2020/4/7 22:07, Paolo Bonzini wrote: > ARM machines and other weakly-ordered architectures have been suffering > for a long time from hangs in qemu-img and qemu-io. For QEMU binaries > these are mitigated by the timers that sooner or later fire in the main > loop, but these will not happen for the tools and probably not with I/O > threads either. yes, we occasionally see qemu main thread hangs and VM stuck in in-shutdown state on aarch64 platform. So this could happen with I/O threads. > > The fix is in patch 5. Patch 1-3 are docs updates that explain the bug, > and patch 4 is a bugfix exposed by the new patch. > > Paolo > > Paolo Bonzini (5): > atomics: convert to reStructuredText > atomics: update documentation > rcu: do not mention atomic_mb_read/set in documentation > aio-wait: delegate polling of main AioContext if BQL not held > async: use explicit memory barriers > > docs/devel/atomics.rst | 501 +++++++++++++++++++++++++++++++++++++++ > docs/devel/atomics.txt | 403 ------------------------------- > docs/devel/index.rst | 1 + > docs/devel/rcu.txt | 4 +- > include/block/aio-wait.h | 22 ++ > include/block/aio.h | 29 +-- > util/aio-posix.c | 16 +- > util/aio-win32.c | 17 +- > util/async.c | 16 +- > 9 files changed, 576 insertions(+), 433 deletions(-) > create mode 100644 docs/devel/atomics.rst > delete mode 100644 docs/devel/atomics.txt >
On 08/04/20 11:12, Ying Fang wrote: > On 2020/4/7 22:07, Paolo Bonzini wrote: >> ARM machines and other weakly-ordered architectures have been suffering >> for a long time from hangs in qemu-img and qemu-io. For QEMU binaries >> these are mitigated by the timers that sooner or later fire in the main >> loop, but these will not happen for the tools and probably not with I/O >> threads either. > > yes, we occasionally see qemu main thread hangs and VM stuck in in-shutdown > state on aarch64 platform. So this could happen with I/O threads. Thanks for confirming! Have you managed to test the final version of the patches? It would be great to include test results. Paolo
On 2020/4/8 23:05, Paolo Bonzini wrote: > On 08/04/20 11:12, Ying Fang wrote: >> On 2020/4/7 22:07, Paolo Bonzini wrote: >>> ARM machines and other weakly-ordered architectures have been suffering >>> for a long time from hangs in qemu-img and qemu-io. For QEMU binaries >>> these are mitigated by the timers that sooner or later fire in the main >>> loop, but these will not happen for the tools and probably not with I/O >>> threads either. >> >> yes, we occasionally see qemu main thread hangs and VM stuck in in-shutdown >> state on aarch64 platform. So this could happen with I/O threads. > > Thanks for confirming! Have you managed to test the final version of > the patches? It would be great to include test results. Yes, I did the test with your latest patches on both aarch64 and x86 platform.Test results show that the hang has been fixed. Thanks. > > Paolo > > >
On Tue, Apr 07, 2020 at 10:07:41AM -0400, Paolo Bonzini wrote: > ARM machines and other weakly-ordered architectures have been suffering > for a long time from hangs in qemu-img and qemu-io. For QEMU binaries > these are mitigated by the timers that sooner or later fire in the main > loop, but these will not happen for the tools and probably not with I/O > threads either. > > The fix is in patch 5. Patch 1-3 are docs updates that explain the bug, > and patch 4 is a bugfix exposed by the new patch. > > Paolo > > Paolo Bonzini (5): > atomics: convert to reStructuredText > atomics: update documentation > rcu: do not mention atomic_mb_read/set in documentation > aio-wait: delegate polling of main AioContext if BQL not held > async: use explicit memory barriers > > docs/devel/atomics.rst | 501 +++++++++++++++++++++++++++++++++++++++ > docs/devel/atomics.txt | 403 ------------------------------- > docs/devel/index.rst | 1 + > docs/devel/rcu.txt | 4 +- > include/block/aio-wait.h | 22 ++ > include/block/aio.h | 29 +-- > util/aio-posix.c | 16 +- > util/aio-win32.c | 17 +- > util/async.c | 16 +- > 9 files changed, 576 insertions(+), 433 deletions(-) > create mode 100644 docs/devel/atomics.rst > delete mode 100644 docs/devel/atomics.txt Applied patches 4 and 5 to my block branch. Stefan