[PATCH v3 3/3] thread-pool: use ThreadPool from the running thread

[Emanuele Giuseppe Esposito]

Use qemu_get_current_aio_context() where possible, since we always
submit work to the current thread anyways.

We want to also be sure that the thread submitting the work is
the same as the one processing the pool, to avoid adding
synchronization to the pool list.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
---
 block/file-posix.c    | 21 ++++++++++-----------
 block/file-win32.c    |  2 +-
 block/qcow2-threads.c |  2 +-
 util/thread-pool.c    |  5 ++++-
 4 files changed, 16 insertions(+), 14 deletions(-)

diff --git a/block/file-posix.c b/block/file-posix.c
index 3800dbd222..28f12b08c8 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -2044,11 +2044,10 @@ out:
     return result;
 }
 
-static int coroutine_fn raw_thread_pool_submit(BlockDriverState *bs,
-                                               ThreadPoolFunc func, void *arg)
+static int coroutine_fn raw_thread_pool_submit(ThreadPoolFunc func, void *arg)
 {
     /* @bs can be NULL, bdrv_get_aio_context() returns the main context then */
-    ThreadPool *pool = aio_get_thread_pool(bdrv_get_aio_context(bs));
+    ThreadPool *pool = aio_get_thread_pool(qemu_get_current_aio_context());
     return thread_pool_submit_co(pool, func, arg);
 }
 
@@ -2116,7 +2115,7 @@ static int coroutine_fn raw_co_prw(BlockDriverState *bs, 
uint64_t offset,
     };
 
     assert(qiov->size == bytes);
-    return raw_thread_pool_submit(bs, handle_aiocb_rw, &acb);
+    return raw_thread_pool_submit(handle_aiocb_rw, &acb);
 }
 
 static int coroutine_fn raw_co_preadv(BlockDriverState *bs, int64_t offset,
@@ -2186,7 +2185,7 @@ static int coroutine_fn 
raw_co_flush_to_disk(BlockDriverState *bs)
         return luring_co_submit(bs, s->fd, 0, NULL, QEMU_AIO_FLUSH);
     }
 #endif
-    return raw_thread_pool_submit(bs, handle_aiocb_flush, &acb);
+    return raw_thread_pool_submit(handle_aiocb_flush, &acb);
 }
 
 static void raw_aio_attach_aio_context(BlockDriverState *bs,
@@ -2248,7 +2247,7 @@ raw_regular_truncate(BlockDriverState *bs, int fd, 
int64_t offset,
         },
     };
 
-    return raw_thread_pool_submit(bs, handle_aiocb_truncate, &acb);
+    return raw_thread_pool_submit(handle_aiocb_truncate, &acb);
 }
 
 static int coroutine_fn raw_co_truncate(BlockDriverState *bs, int64_t offset,
@@ -2998,7 +2997,7 @@ raw_do_pdiscard(BlockDriverState *bs, int64_t offset, 
int64_t bytes,
         acb.aio_type |= QEMU_AIO_BLKDEV;
     }
 
-    ret = raw_thread_pool_submit(bs, handle_aiocb_discard, &acb);
+    ret = raw_thread_pool_submit(handle_aiocb_discard, &acb);
     raw_account_discard(s, bytes, ret);
     return ret;
 }
@@ -3073,7 +3072,7 @@ raw_do_pwrite_zeroes(BlockDriverState *bs, int64_t 
offset, int64_t bytes,
         handler = handle_aiocb_write_zeroes;
     }
 
-    return raw_thread_pool_submit(bs, handler, &acb);
+    return raw_thread_pool_submit(handler, &acb);
 }
 
 static int coroutine_fn raw_co_pwrite_zeroes(
@@ -3284,7 +3283,7 @@ static int coroutine_fn 
raw_co_copy_range_to(BlockDriverState *bs,
         },
     };
 
-    return raw_thread_pool_submit(bs, handle_aiocb_copy_range, &acb);
+    return raw_thread_pool_submit(handle_aiocb_copy_range, &acb);
 }
 
 BlockDriver bdrv_file = {
@@ -3614,7 +3613,7 @@ hdev_co_ioctl(BlockDriverState *bs, unsigned long int 
req, void *buf)
         struct sg_io_hdr *io_hdr = buf;
         if (io_hdr->cmdp[0] == PERSISTENT_RESERVE_OUT ||
             io_hdr->cmdp[0] == PERSISTENT_RESERVE_IN) {
-            return pr_manager_execute(s->pr_mgr, bdrv_get_aio_context(bs),
+            return pr_manager_execute(s->pr_mgr, 
qemu_get_current_aio_context(),
                                       s->fd, io_hdr);
         }
     }
@@ -3630,7 +3629,7 @@ hdev_co_ioctl(BlockDriverState *bs, unsigned long int 
req, void *buf)
         },
     };
 
-    return raw_thread_pool_submit(bs, handle_aiocb_ioctl, &acb);
+    return raw_thread_pool_submit(handle_aiocb_ioctl, &acb);
 }
 #endif /* linux */
 
diff --git a/block/file-win32.c b/block/file-win32.c
index ec9d64d0e4..3d7f59a592 100644
--- a/block/file-win32.c
+++ b/block/file-win32.c
@@ -167,7 +167,7 @@ static BlockAIOCB *paio_submit(BlockDriverState *bs, HANDLE 
hfile,
     acb->aio_offset = offset;
 
     trace_file_paio_submit(acb, opaque, offset, count, type);
-    pool = aio_get_thread_pool(bdrv_get_aio_context(bs));
+    pool = aio_get_thread_pool(qemu_get_current_aio_context());
     return thread_pool_submit_aio(pool, aio_worker, acb, cb, opaque);
 }
 
diff --git a/block/qcow2-threads.c b/block/qcow2-threads.c
index 1914baf456..9e370acbb3 100644
--- a/block/qcow2-threads.c
+++ b/block/qcow2-threads.c
@@ -42,7 +42,7 @@ qcow2_co_process(BlockDriverState *bs, ThreadPoolFunc *func, 
void *arg)
 {
     int ret;
     BDRVQcow2State *s = bs->opaque;
-    ThreadPool *pool = aio_get_thread_pool(bdrv_get_aio_context(bs));
+    ThreadPool *pool = aio_get_thread_pool(qemu_get_current_aio_context());
 
     qemu_co_mutex_lock(&s->lock);
     while (s->nb_threads >= QCOW2_MAX_THREADS) {
diff --git a/util/thread-pool.c b/util/thread-pool.c
index 31113b5860..0e26687e97 100644
--- a/util/thread-pool.c
+++ b/util/thread-pool.c
@@ -48,7 +48,7 @@ struct ThreadPoolElement {
     /* Access to this list is protected by lock.  */
     QTAILQ_ENTRY(ThreadPoolElement) reqs;
 
-    /* Access to this list is protected by the global mutex.  */
+    /* This list is only written by the thread pool's mother thread.  */
     QLIST_ENTRY(ThreadPoolElement) all;
 };
 
@@ -251,6 +251,9 @@ BlockAIOCB *thread_pool_submit_aio(ThreadPool *pool,
 {
     ThreadPoolElement *req;
 
+    /* Assert that the thread submitting work is the same running the pool */
+    assert(pool->ctx == qemu_get_current_aio_context());
+
     req = qemu_aio_get(&thread_pool_aiocb_info, NULL, cb, opaque);
     req->func = func;
     req->arg = arg;
-- 
2.31.1