Block jobs will run in the BlockDriverState's AioContext, which may not
always be the QEMU main loop.
There are some block layer APIs that are either not thread-safe or risk
lock ordering problems. This includes bdrv_unref(), bdrv_close(), and
anything that calls bdrv_drain_all().
The block_job_defer_to_main_loop() API allows a block job to schedule a
function to run in the main loop with the BlockDriverState AioContext
held.
This function will be used to perform cleanup and backing chain
manipulations in block jobs.
Signed-off-by: Stefan Hajnoczi <address@hidden>
---
blockjob.c | 35 +++++++++++++++++++++++++++++++++++
include/block/blockjob.h | 19 +++++++++++++++++++
2 files changed, 54 insertions(+)
diff --git a/blockjob.c b/blockjob.c
index 0689fdd..24a64d8 100644
--- a/blockjob.c
+++ b/blockjob.c
@@ -313,3 +313,38 @@ BlockErrorAction block_job_error_action(BlockJob *job,
BlockDriverState *bs,
}
return action;
}
+
+typedef struct {
+ BlockJob *job;
+ QEMUBH *bh;
+ AioContext *aio_context;
+ BlockJobDeferToMainLoopFn *fn;
+ void *opaque;
+} BlockJobDeferToMainLoopData;
+
+static void block_job_defer_to_main_loop_bh(void *opaque)
+{
+ BlockJobDeferToMainLoopData *data = opaque;
+
+ qemu_bh_delete(data->bh);
+
+ aio_context_acquire(data->aio_context);
+ data->fn(data->job, data->opaque);
+ aio_context_release(data->aio_context);
+
+ g_free(data);
+}
+
+void block_job_defer_to_main_loop(BlockJob *job,
+ BlockJobDeferToMainLoopFn *fn,
+ void *opaque)
+{
+ BlockJobDeferToMainLoopData *data = g_malloc(sizeof(*data));
+ data->job = job;
+ data->bh = qemu_bh_new(block_job_defer_to_main_loop_bh, data);
+ data->aio_context = bdrv_get_aio_context(job->bs);
+ data->fn = fn;
+ data->opaque = opaque;
+
+ qemu_bh_schedule(data->bh);
+}