Add co_wrapper_bdrv_rdlock and co_wrapper_mixed_bdrv_rdlock option to
the block-coroutine-wrapper.py script.
This "_bdrv_rdlock" option takes and releases the graph rdlock when a
coroutine function is created.
This means that when used together with "_mixed", the function marked
with co_wrapper_mixed_bdrv_rdlock will support both coroutine and
non-coroutine case, and in the latter case it will create a coroutine
that takes and releases the rdlock. When called from a coroutine, the
caller must already hold the graph lock.
Example:
void co_wrapper_mixed_bdrv_rdlock bdrv_f1();
Becomes
static void bdrv_co_enter_f1()
{
bdrv_graph_co_rdlock();
bdrv_co_function();
bdrv_graph_co_rdunlock();
}
void bdrv_f1()
{
if (qemu_in_coroutine) {
assume_graph_lock();
bdrv_co_function();
} else {
qemu_co_enter(bdrv_co_enter_f1);
...
}
}
When used alone, the function will not work in coroutine context, and
when called in non-coroutine context it will create a new coroutine that
takes care of taking and releasing the rdlock automatically.
Example:
void co_wrapper_bdrv_rdlock bdrv_f1();
Becomes
static void bdrv_co_enter_f1()
{
bdrv_graph_co_rdlock();
bdrv_co_function();
bdrv_graph_co_rdunlock();
}
void bdrv_f1()
{
assert(!qemu_in_coroutine());
qemu_co_enter(bdrv_co_enter_f1);
...
}
About their usage:
- co_wrapper does not take the rdlock, so it can be used also outside
the block layer.
- co_wrapper_mixed will be used by many blk_* functions, since the
coroutine function needs to call blk_wait_while_drained() and
the rdlock *must* be taken afterwards, otherwise it's a deadlock.
In the future this annotation will go away, and blk_* will use
co_wrapper directly.
- co_wrapper_bdrv_rdlock will be used by BlockDriver callbacks, ideally
by all of them in the future.
- co_wrapper_mixed_bdrv_rdlock will be used by the remaining functions
that are still called by coroutine and non-coroutine context. In the
future this annotation will go away, as we will split such mixed
functions.
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20221207131838.239125-17-kwolf@redhat.com>
Reviewed-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
e6d3f7a602