From f0d43b1ecef04105e0d0f55658182510b4e0f58e Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Wed, 27 Apr 2022 15:08:30 +0200 Subject: [PATCH] coroutine-lock: qemu_co_queue_restart_all is a coroutine-only qemu_co_enter_all qemu_co_queue_restart_all is basically the same as qemu_co_enter_all 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_restart_all 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 to qemu_co_queue_restart_all and to its sole non-coroutine_fn caller; it then reimplements the function in terms of qemu_co_enter_all_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: <20220427130830.150180-4-pbonzini@redhat.com> Signed-off-by: Paolo Bonzini --- block/io.c | 2 +- include/qemu/coroutine.h | 7 ++++--- util/qemu-coroutine-lock.c | 21 ++++++--------------- 3 files changed, 11 insertions(+), 19 deletions(-) diff --git a/block/io.c b/block/io.c index 9769ec53b0..789e6373d5 100644 --- a/block/io.c +++ b/block/io.c @@ -751,7 +751,7 @@ void bdrv_drain_all(void) * * This function should be called when a tracked request is completing. */ -static void tracked_request_end(BdrvTrackedRequest *req) +static void coroutine_fn tracked_request_end(BdrvTrackedRequest *req) { if (req->serialising) { qatomic_dec(&req->bs->serialising_in_flight); diff --git a/include/qemu/coroutine.h b/include/qemu/coroutine.h index e5954635f6..43df7a7e66 100644 --- a/include/qemu/coroutine.h +++ b/include/qemu/coroutine.h @@ -216,10 +216,11 @@ void coroutine_fn qemu_co_queue_wait_impl(CoQueue *queue, QemuLockable *lock); bool coroutine_fn qemu_co_queue_next(CoQueue *queue); /** - * Empties the CoQueue; all coroutines are woken up. - * OK to run from coroutine and non-coroutine context. + * Empties the CoQueue and queues the coroutine to run after + * the currently-running coroutine yields. + * Used from coroutine context, use qemu_co_enter_all outside. */ -void qemu_co_queue_restart_all(CoQueue *queue); +void coroutine_fn qemu_co_queue_restart_all(CoQueue *queue); /** * Removes the next coroutine from the CoQueue, and wake it up. Unlike diff --git a/util/qemu-coroutine-lock.c b/util/qemu-coroutine-lock.c index 5b0342faed..9ad24ab1af 100644 --- a/util/qemu-coroutine-lock.c +++ b/util/qemu-coroutine-lock.c @@ -67,21 +67,6 @@ void coroutine_fn qemu_co_queue_wait_impl(CoQueue *queue, QemuLockable *lock) } } -void qemu_co_queue_restart_all(CoQueue *queue) -{ - Coroutine *next; - - if (QSIMPLEQ_EMPTY(&queue->entries)) { - return false; - } - - while ((next = QSIMPLEQ_FIRST(&queue->entries)) != NULL) { - QSIMPLEQ_REMOVE_HEAD(&queue->entries, co_queue_next); - aio_co_wake(next); - } - return true; -} - bool qemu_co_enter_next_impl(CoQueue *queue, QemuLockable *lock) { Coroutine *next; @@ -115,6 +100,12 @@ void qemu_co_enter_all_impl(CoQueue *queue, QemuLockable *lock) } } +void coroutine_fn qemu_co_queue_restart_all(CoQueue *queue) +{ + /* No unlock/lock needed in coroutine context. */ + qemu_co_enter_all_impl(queue, NULL); +} + bool qemu_co_queue_empty(CoQueue *queue) { return QSIMPLEQ_FIRST(&queue->entries) == NULL;