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coroutine-lock: qemu_co_queue_next is a coroutine-only qemu_co_enter_next

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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 <pbonzini@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20220427130830.150180-2-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2022-04-27 15:08:28 +02:00
parent bf2f69d08b
commit 248af9e80a
2 changed files with 11 additions and 17 deletions
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7
include/qemu/coroutine.h
View File

@ -208,11 +208,12 @@ void qemu_co_queue_init(CoQueue *queue);
void coroutine_fn qemu_co_queue_wait_impl(CoQueue *queue, QemuLockable *lock); 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. * 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. * Empties the CoQueue; all coroutines are woken up.

21
util/qemu-coroutine-lock.c
View File

@ -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; Coroutine *next;
@ -78,23 +78,10 @@ static bool qemu_co_queue_do_restart(CoQueue *queue, bool single)
while ((next = QSIMPLEQ_FIRST(&queue->entries)) != NULL) { while ((next = QSIMPLEQ_FIRST(&queue->entries)) != NULL) {
QSIMPLEQ_REMOVE_HEAD(&queue->entries, co_queue_next); QSIMPLEQ_REMOVE_HEAD(&queue->entries, co_queue_next);
aio_co_wake(next); aio_co_wake(next);
if (single) {
break;
}
} }
return true; 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) bool qemu_co_enter_next_impl(CoQueue *queue, QemuLockable *lock)
{ {
Coroutine *next; Coroutine *next;
@ -115,6 +102,12 @@ bool qemu_co_enter_next_impl(CoQueue *queue, QemuLockable *lock)
return true; 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) bool qemu_co_queue_empty(CoQueue *queue)
{ {
return QSIMPLEQ_FIRST(&queue->entries) == NULL; return QSIMPLEQ_FIRST(&queue->entries) == NULL;