From 248af9e80a04c5ab4ffec789aa24345d3d86b42b Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Wed, 27 Apr 2022 15:08:28 +0200 Subject: [PATCH] coroutine-lock: qemu_co_queue_next is a coroutine-only qemu_co_enter_next qemu_co_queue_next is basically the same as qemu_co_enter_next but without a QemuLockable argument. That's perfectly fine, but only as long as the function is marked coroutine_fn. If used outside coroutine context, qemu_co_queue_wait will attempt to take the lock and that is just broken: if you are calling qemu_co_queue_next outside coroutine context, the lock is going to be a QemuMutex which cannot be taken twice by the same thread. The patch adds the marker and reimplements qemu_co_queue_next in terms of qemu_co_enter_next_impl, to remove duplicated code and to clarify that the latter also works in coroutine context. Signed-off-by: Paolo Bonzini Reviewed-by: Eric Blake Message-Id: <20220427130830.150180-2-pbonzini@redhat.com> Signed-off-by: Paolo Bonzini --- include/qemu/coroutine.h | 7 ++++--- util/qemu-coroutine-lock.c | 21 +++++++-------------- 2 files changed, 11 insertions(+), 17 deletions(-) diff --git a/include/qemu/coroutine.h b/include/qemu/coroutine.h index 284571badb..c23d41e1ff 100644 --- a/include/qemu/coroutine.h +++ b/include/qemu/coroutine.h @@ -208,11 +208,12 @@ void qemu_co_queue_init(CoQueue *queue); void coroutine_fn qemu_co_queue_wait_impl(CoQueue *queue, QemuLockable *lock); /** - * Removes the next coroutine from the CoQueue, and wake it up. + * Removes the next coroutine from the CoQueue, and queue it to run after + * the currently-running coroutine yields. * Returns true if a coroutine was removed, false if the queue is empty. - * OK to run from coroutine and non-coroutine context. + * Used from coroutine context, use qemu_co_enter_next outside. */ -bool qemu_co_queue_next(CoQueue *queue); +bool coroutine_fn qemu_co_queue_next(CoQueue *queue); /** * Empties the CoQueue; all coroutines are woken up. diff --git a/util/qemu-coroutine-lock.c b/util/qemu-coroutine-lock.c index 2669403839..5705cfea2e 100644 --- a/util/qemu-coroutine-lock.c +++ b/util/qemu-coroutine-lock.c @@ -67,7 +67,7 @@ void coroutine_fn qemu_co_queue_wait_impl(CoQueue *queue, QemuLockable *lock) } } -static bool qemu_co_queue_do_restart(CoQueue *queue, bool single) +void qemu_co_queue_restart_all(CoQueue *queue) { Coroutine *next; @@ -78,23 +78,10 @@ static bool qemu_co_queue_do_restart(CoQueue *queue, bool single) while ((next = QSIMPLEQ_FIRST(&queue->entries)) != NULL) { QSIMPLEQ_REMOVE_HEAD(&queue->entries, co_queue_next); aio_co_wake(next); - if (single) { - break; - } } return true; } -bool qemu_co_queue_next(CoQueue *queue) -{ - return qemu_co_queue_do_restart(queue, true); -} - -void qemu_co_queue_restart_all(CoQueue *queue) -{ - qemu_co_queue_do_restart(queue, false); -} - bool qemu_co_enter_next_impl(CoQueue *queue, QemuLockable *lock) { Coroutine *next; @@ -115,6 +102,12 @@ bool qemu_co_enter_next_impl(CoQueue *queue, QemuLockable *lock) return true; } +bool coroutine_fn qemu_co_queue_next(CoQueue *queue) +{ + /* No unlock/lock needed in coroutine context. */ + return qemu_co_enter_next_impl(queue, NULL); +} + bool qemu_co_queue_empty(CoQueue *queue) { return QSIMPLEQ_FIRST(&queue->entries) == NULL;