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
v4->v5: fix checkpatch complaints
v3->v4: fix -O0 compilation [Fam]
typos and copyright dates [Eric, Fam]
improve CoQueue comments [Stefan]
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 | 29 +++++++++-----
include/qemu/lockable.h | 96 +++++++++++++++++++++++++++++++++++++++++++++
include/qemu/thread.h | 5 +--
include/qemu/typedefs.h | 4 ++
tests/test-coroutine.c | 75 ++++++++++++++++++++++++++++++++++-
util/qemu-coroutine-lock.c | 22 +++++++----
9 files changed, 256 insertions(+), 39 deletions(-)
create mode 100644 include/qemu/lockable.h
--
2.14.3
