[PATCH v3 5/5] block-coroutine-wrapper: use qemu_get_current_aio_context()

[Stefan Hajnoczi]

Use qemu_get_current_aio_context() in mixed wrappers and coroutine
wrappers so that code runs in the caller's AioContext instead of moving
to the BlockDriverState's AioContext. This change is necessary for the
multi-queue block layer where any thread can call into the block layer.

Most wrappers are IO_CODE where it's safe to use the current AioContext
nowadays. BlockDrivers and the core block layer use their own locks and
no longer depend on the AioContext lock for thread-safety.

The bdrv_create() wrapper invokes GLOBAL_STATE code. Using the current
AioContext is safe because this code is only called with the BQL held
from the main loop thread.

The output of qemu-iotests 051 is sensitive to event loop activity.
Update the output because the monitor BH runs at a different time,
causing prompts to be printed differently in the output.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 scripts/block-coroutine-wrapper.py | 6 ++----
 tests/qemu-iotests/051.pc.out      | 4 ++--
 2 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/scripts/block-coroutine-wrapper.py 
b/scripts/block-coroutine-wrapper.py
index d4a183db61..f93fe154c3 100644
--- a/scripts/block-coroutine-wrapper.py
+++ b/scripts/block-coroutine-wrapper.py
@@ -88,8 +88,6 @@ def __init__(self, wrapper_type: str, return_type: str, name: 
str,
                 raise ValueError(f"no_co function can't be rdlock: 
{self.name}")
             self.target_name = f'{subsystem}_{subname}'
 
-        self.ctx = self.gen_ctx()
-
         self.get_result = 's->ret = '
         self.ret = 'return s.ret;'
         self.co_ret = 'return '
@@ -162,7 +160,7 @@ def create_mixed_wrapper(func: FuncDecl) -> str:
         {func.co_ret}{name}({ func.gen_list('{name}') });
     }} else {{
         {struct_name} s = {{
-            .poll_state.ctx = {func.ctx},
+            .poll_state.ctx = qemu_get_current_aio_context(),
             .poll_state.in_progress = true,
 
 { func.gen_block('            .{name} = {name},') }
@@ -186,7 +184,7 @@ def create_co_wrapper(func: FuncDecl) -> str:
 {func.return_type} {func.name}({ func.gen_list('{decl}') })
 {{
     {struct_name} s = {{
-        .poll_state.ctx = {func.ctx},
+        .poll_state.ctx = qemu_get_current_aio_context(),
         .poll_state.in_progress = true,
 
 { func.gen_block('        .{name} = {name},') }
diff --git a/tests/qemu-iotests/051.pc.out b/tests/qemu-iotests/051.pc.out
index 4d4af5a486..650cfed8e2 100644
--- a/tests/qemu-iotests/051.pc.out
+++ b/tests/qemu-iotests/051.pc.out
@@ -177,11 +177,11 @@ QEMU_PROG: -device virtio-blk-pci,drive=disk,share-rw=on: 
Cannot change iothread
 
 Testing: -drive file=TEST_DIR/t.qcow2,if=none,node-name=disk -object 
iothread,id=thread0 -device virtio-scsi,iothread=thread0,id=virtio-scsi0 
-device scsi-hd,bus=virtio-scsi0.0,drive=disk,share-rw=on -device 
lsi53c895a,id=lsi0 -device scsi-hd,bus=lsi0.0,drive=disk,share-rw=on
 QEMU X.Y.Z monitor - type 'help' for more information
-(qemu) QEMU_PROG: -device scsi-hd,bus=lsi0.0,drive=disk,share-rw=on: HBA does 
not support iothreads
+QEMU_PROG: -device scsi-hd,bus=lsi0.0,drive=disk,share-rw=on: HBA does not 
support iothreads
 
 Testing: -drive file=TEST_DIR/t.qcow2,if=none,node-name=disk -object 
iothread,id=thread0 -device virtio-scsi,iothread=thread0,id=virtio-scsi0 
-device scsi-hd,bus=virtio-scsi0.0,drive=disk,share-rw=on -device 
virtio-scsi,id=virtio-scsi1 -device 
scsi-hd,bus=virtio-scsi1.0,drive=disk,share-rw=on
 QEMU X.Y.Z monitor - type 'help' for more information
-(qemu) QEMU_PROG: -device scsi-hd,bus=virtio-scsi1.0,drive=disk,share-rw=on: 
Cannot change iothread of active block backend
+QEMU_PROG: -device scsi-hd,bus=virtio-scsi1.0,drive=disk,share-rw=on: Cannot 
change iothread of active block backend
 
 Testing: -drive file=TEST_DIR/t.qcow2,if=none,node-name=disk -object 
iothread,id=thread0 -device virtio-scsi,iothread=thread0,id=virtio-scsi0 
-device scsi-hd,bus=virtio-scsi0.0,drive=disk,share-rw=on -device 
virtio-blk-pci,drive=disk,iothread=thread0,share-rw=on
 QEMU X.Y.Z monitor - type 'help' for more information
-- 
2.41.0