There are cases in which a queued coroutine must be restarted from non-coroutine context (with qemu_co_enter_next). In this cases, qemu_co_enter_next also needs to be thread-safe, but it cannot use a CoMutex and so cannot qemu_co_queue_wait. This happens in curl (which right now is rolling its own list of Coroutines) and will happen in Fam's NVMe driver as well.
This series extracts the idea of a polymorphic lockable object from my "scoped lock guard" proposal, and applies it to CoQueue. The implementation of QemuLockable is similar to C11 _Generic, but redone using the preprocessor and GCC builtins for compatibility. In general, while a bit on the esoteric side, the functionality used to emulate _Generic is fairly old in GCC, and the builtins are already used by include/qemu/atomic.h; the series was tested with Fedora 27 (boot Damn Small Linux via http) and CentOS 6 (compiled only). Paolo v1->v2: fix typos and copyright year v2->v3: add tests, fix brown paper bag bug, avoid -Waddress errors Paolo Bonzini (5): test-coroutine: add simple CoMutex test lockable: add QemuLockable coroutine-lock: convert CoQueue to use QemuLockable coroutine-lock: make qemu_co_enter_next thread-safe curl: convert to CoQueue block/curl.c | 20 +++-------- fsdev/qemu-fsdev-throttle.c | 4 +-- include/qemu/compiler.h | 40 +++++++++++++++++++++ include/qemu/coroutine.h | 25 ++++++++----- include/qemu/lockable.h | 88 +++++++++++++++++++++++++++++++++++++++++++++ include/qemu/thread.h | 5 ++- include/qemu/typedefs.h | 4 +++ tests/test-coroutine.c | 75 ++++++++++++++++++++++++++++++++++++-- util/qemu-coroutine-lock.c | 22 ++++++++---- 9 files changed, 245 insertions(+), 38 deletions(-) create mode 100644 include/qemu/lockable.h -- 2.14.3
