[Qemu-devel] [PATCH] block: Acquire the AioContext in guess_disk_lchs()

[Alberto Garcia <berto@igalia.com>]

This fixes the following crash:

{ "execute": "blockdev-add",
  "arguments": {"driver": "null-co", "node-name": "hd0"}}
{ "execute": "object-add",
  "arguments": {"qom-type": "iothread", "id": "iothread0"}}
{ "execute": "x-blockdev-set-iothread",
  "arguments": {"node-name": "hd0", "iothread": "iothread0"}}
{ "execute": "device_add",
  "arguments": {"id": "virtio0", "driver": "virtio-blk-pci",
                "drive": "hd0"}}
qemu: qemu_mutex_unlock_impl: Operation not permitted
Aborted

Signed-off-by: Alberto Garcia <berto@igalia.com>
---
 hw/block/hd-geometry.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/hw/block/hd-geometry.c b/hw/block/hd-geometry.c
index 79384a2b0a..0d9a7b7e7d 100644
--- a/hw/block/hd-geometry.c
+++ b/hw/block/hd-geometry.c
@@ -55,6 +55,7 @@ struct partition {
 static int guess_disk_lchs(BlockBackend *blk,
                            int *pcylinders, int *pheads, int *psectors)
 {
+    AioContext *ctx = blk_get_aio_context(blk);
     uint8_t buf[BDRV_SECTOR_SIZE];
     int i, heads, sectors, cylinders;
     struct partition *p;
@@ -68,7 +69,10 @@ static int guess_disk_lchs(BlockBackend *blk,
      * but also in async I/O mode. So the I/O throttling function has to
      * be disabled temporarily here, not permanently.
      */
-    if (blk_pread_unthrottled(blk, 0, buf, BDRV_SECTOR_SIZE) < 0) {
+    aio_context_acquire(ctx);
+    i = blk_pread_unthrottled(blk, 0, buf, BDRV_SECTOR_SIZE);
+    aio_context_release(ctx);
+    if (i < 0) {
         return -1;
     }
     /* test msdos magic */
-- 
2.11.0