@@ -65,6 +65,9 @@
* scheduling a BH in the bottom half that runs the respective non-coroutine
* function. The coroutine yields after scheduling the BH and is reentered when
* the wrapped function returns.
+ *
+ * If the first parameter of the function is a BlockDriverState, BdrvChild or
+ * BlockBackend pointer, the AioContext lock for it is taken in the wrapper.
*/
#define no_co_wrapper
@@ -2394,9 +2394,14 @@ void blk_op_unblock_all(BlockBackend *blk, Error *reason)
AioContext *blk_get_aio_context(BlockBackend *blk)
{
- BlockDriverState *bs = blk_bs(blk);
+ BlockDriverState *bs;
IO_CODE();
+ if (!blk) {
+ return qemu_get_aio_context();
+ }
+
+ bs = blk_bs(blk);
if (bs) {
AioContext *ctx = bdrv_get_aio_context(blk_bs(blk));
assert(ctx == blk->ctx);
@@ -88,16 +88,7 @@ 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}'
- t = self.args[0].type
- if t == 'BlockDriverState *':
- ctx = 'bdrv_get_aio_context(bs)'
- elif t == 'BdrvChild *':
- ctx = 'bdrv_get_aio_context(child->bs)'
- elif t == 'BlockBackend *':
- ctx = 'blk_get_aio_context(blk)'
- else:
- ctx = 'qemu_get_aio_context()'
- self.ctx = ctx
+ self.ctx = self.gen_ctx()
self.get_result = 's->ret = '
self.ret = 'return s.ret;'
@@ -109,6 +100,17 @@ def __init__(self, wrapper_type: str, return_type: str, name: str,
self.co_ret = ''
self.return_field = ''
+ def gen_ctx(self, prefix: str = '') -> str:
+ t = self.args[0].type
+ if t == 'BlockDriverState *':
+ return f'bdrv_get_aio_context({prefix}bs)'
+ elif t == 'BdrvChild *':
+ return f'bdrv_get_aio_context({prefix}child->bs)'
+ elif t == 'BlockBackend *':
+ return f'blk_get_aio_context({prefix}blk)'
+ else:
+ return 'qemu_get_aio_context()'
+
def gen_list(self, format: str) -> str:
return ', '.join(format.format_map(arg.__dict__) for arg in self.args)
@@ -262,8 +264,11 @@ def gen_no_co_wrapper(func: FuncDecl) -> str:
static void {name}_bh(void *opaque)
{{
{struct_name} *s = opaque;
+ AioContext *ctx = {func.gen_ctx('s->')};
+ aio_context_acquire(ctx);
{func.get_result}{name}({ func.gen_list('s->{name}') });
+ aio_context_release(ctx);
aio_co_wake(s->co);
}}
All of the functions that currently take a BlockDriverState, BdrvChild or BlockBackend as their first parameter expect the associated AioContext to be locked when they are called. In the case of no_co_wrappers, they are called from bottom halves directly in the main loop, so no other caller can be expected to take the lock for them. This can result in assertion failures because a lock that isn't taken is released in nested event loops. Looking at the first parameter is already done by co_wrappers to decide where the coroutine should run, so doing the same in no_co_wrappers is only consistent. Take the lock in the generated bottom halves to fix the problem. Signed-off-by: Kevin Wolf <kwolf@redhat.com> --- include/block/block-common.h | 3 +++ block/block-backend.c | 7 ++++++- scripts/block-coroutine-wrapper.py | 25 +++++++++++++++---------- 3 files changed, 24 insertions(+), 11 deletions(-)