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[Qemu-devel] [PULL 47/53] blockjob: add block_job_defer_to_main_loop()
From: |
Stefan Hajnoczi |
Subject: |
[Qemu-devel] [PULL 47/53] blockjob: add block_job_defer_to_main_loop() |
Date: |
Mon, 3 Nov 2014 11:50:50 +0000 |
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>
Reviewed-by: Max Reitz <address@hidden>
Message-id: address@hidden
---
blockjob.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
include/block/blockjob.h | 19 +++++++++++++++++++
2 files changed, 64 insertions(+)
diff --git a/blockjob.c b/blockjob.c
index 448b9ce..cd4b573 100644
--- a/blockjob.c
+++ b/blockjob.c
@@ -342,3 +342,48 @@ 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;
+ AioContext *aio_context;
+
+ qemu_bh_delete(data->bh);
+
+ /* Prevent race with block_job_defer_to_main_loop() */
+ aio_context_acquire(data->aio_context);
+
+ /* Fetch BDS AioContext again, in case it has changed */
+ aio_context = bdrv_get_aio_context(data->job->bs);
+ aio_context_acquire(aio_context);
+
+ data->fn(data->job, data->opaque);
+
+ aio_context_release(aio_context);
+
+ 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);
+}
diff --git a/include/block/blockjob.h b/include/block/blockjob.h
index 9694f13..b6d4ebb 100644
--- a/include/block/blockjob.h
+++ b/include/block/blockjob.h
@@ -315,4 +315,23 @@ void block_job_iostatus_reset(BlockJob *job);
BlockErrorAction block_job_error_action(BlockJob *job, BlockDriverState *bs,
BlockdevOnError on_err,
int is_read, int error);
+
+typedef void BlockJobDeferToMainLoopFn(BlockJob *job, void *opaque);
+
+/**
+ * block_job_defer_to_main_loop:
+ * @job: The job
+ * @fn: The function to run in the main loop
+ * @opaque: The opaque value that is passed to @fn
+ *
+ * Execute a given function in the main loop with the BlockDriverState
+ * AioContext acquired. Block jobs must call bdrv_unref(), bdrv_close(), and
+ * anything that uses bdrv_drain_all() in the main loop.
+ *
+ * The @job AioContext is held while @fn executes.
+ */
+void block_job_defer_to_main_loop(BlockJob *job,
+ BlockJobDeferToMainLoopFn *fn,
+ void *opaque);
+
#endif
--
1.9.3
- [Qemu-devel] [PULL 37/53] qemu-img: Add progress output for amend, (continued)
- [Qemu-devel] [PULL 37/53] qemu-img: Add progress output for amend, Stefan Hajnoczi, 2014/11/03
- [Qemu-devel] [PULL 38/53] qemu-img: Fix insignificant memleak, Stefan Hajnoczi, 2014/11/03
- [Qemu-devel] [PULL 39/53] block/qcow2: Implement status CB for amend, Stefan Hajnoczi, 2014/11/03
- [Qemu-devel] [PULL 40/53] block/qcow2: Make get_refcount() global, Stefan Hajnoczi, 2014/11/03
- [Qemu-devel] [PULL 41/53] block/qcow2: Simplify shared L2 handling in amend, Stefan Hajnoczi, 2014/11/03
- [Qemu-devel] [PULL 42/53] iotests: Expand test 061, Stefan Hajnoczi, 2014/11/03
- [Qemu-devel] [PULL 43/53] block: acquire AioContext in generic blockjob QMP commands, Stefan Hajnoczi, 2014/11/03
- [Qemu-devel] [PULL 44/53] blockdev: acquire AioContext in do_qmp_query_block_jobs_one(), Stefan Hajnoczi, 2014/11/03
- [Qemu-devel] [PULL 45/53] blockdev: acquire AioContext in blockdev_mark_auto_del(), Stefan Hajnoczi, 2014/11/03
- [Qemu-devel] [PULL 46/53] blockdev: add note that block_job_cb() must be thread-safe, Stefan Hajnoczi, 2014/11/03
- [Qemu-devel] [PULL 47/53] blockjob: add block_job_defer_to_main_loop(),
Stefan Hajnoczi <=
- [Qemu-devel] [PULL 48/53] block: add bdrv_drain(), Stefan Hajnoczi, 2014/11/03
- [Qemu-devel] [PULL 49/53] block: let backup blockjob run in BDS AioContext, Stefan Hajnoczi, 2014/11/03
- [Qemu-devel] [PULL 50/53] block: let stream blockjob run in BDS AioContext, Stefan Hajnoczi, 2014/11/03
- [Qemu-devel] [PULL 52/53] block: let commit blockjob run in BDS AioContext, Stefan Hajnoczi, 2014/11/03
- [Qemu-devel] [PULL 53/53] block: declare blockjobs and dataplane friends!, Stefan Hajnoczi, 2014/11/03
- [Qemu-devel] [PULL 51/53] block: let mirror blockjob run in BDS AioContext, Stefan Hajnoczi, 2014/11/03
- Re: [Qemu-devel] [PULL 00/53] Block patches, Peter Maydell, 2014/11/03