This is a resubmit of David Edmondson's series at https://patchew.org/QEMU/20210309144015.557477-1-david.edmond...@oracle.com/. After closer analysis on IRC, the CoRwLock's attempt to ensure fairness turned out to be flawed. Therefore, this series reimplements CoRwLock without using a CoQueue. Tracking whether each queued coroutine is a reader/writer makes it possible to never wake a writer when only readers should be allowed and vice versa.
David Edmondson (4): block/vdi: When writing new bmap entry fails, don't leak the buffer block/vdi: Don't assume that blocks are larger than VdiHeader coroutine/mutex: Store the coroutine in the CoWaitRecord only once test-coroutine: Add rwlock downgrade test Paolo Bonzini (1): coroutine-lock: reimplement CoRwLock to fix downgrade bug block/vdi.c | 11 ++- include/qemu/coroutine.h | 10 ++- tests/unit/test-coroutine.c | 112 ++++++++++++++++++++++++++ util/qemu-coroutine-lock.c | 151 +++++++++++++++++++++++------------- 4 files changed, 225 insertions(+), 59 deletions(-) -- 2.29.2
