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>
*
* Usage: read docs/devel/block-coroutine-wrapper.rst
*
- * There are 2 kind of specifiers:
+ * There are 4 kind of specifiers:
* - co_wrapper functions can be called by only non-coroutine context, because
* they always generate a new coroutine.
* - co_wrapper_mixed functions can be called by both coroutine and
* non-coroutine context.
+ * - co_wrapper_bdrv_rdlock are co_wrapper functions but automatically take and
+ * release the graph rdlock when creating a new coroutine
+ * - co_wrapper_mixed_bdrv_rdlock are co_wrapper_mixed functions but
+ * automatically take and release the graph rdlock when creating a new
+ * coroutine.
*/
#define co_wrapper
#define co_wrapper_mixed
+#define co_wrapper_bdrv_rdlock
+#define co_wrapper_mixed_bdrv_rdlock
#include "block/dirty-bitmap.h"
#include "block/blockjob.h"
self.struct_name = snake_to_camel(self.name)
self.args = [ParamDecl(arg.strip()) for arg in args.split(',')]
self.create_only_co = 'mixed' not in variant
+ self.graph_rdlock = 'bdrv_rdlock' in variant
subsystem, subname = self.name.split('_', 1)
self.co_name = f'{subsystem}_co_{subname}'
"""
name = func.co_name
struct_name = func.struct_name
+ graph_assume_lock = 'assume_graph_lock();' if func.graph_rdlock else ''
+
return f"""\
{func.return_type} {func.name}({ func.gen_list('{decl}') })
{{
if (qemu_in_coroutine()) {{
+ {graph_assume_lock}
return {name}({ func.gen_list('{name}') });
}} else {{
{struct_name} s = {{
name = func.co_name
struct_name = func.struct_name
+ graph_lock=''
+ graph_unlock=''
+ if func.graph_rdlock:
+ graph_lock=' bdrv_graph_co_rdlock();'
+ graph_unlock=' bdrv_graph_co_rdunlock();'
+
creation_function = create_mixed_wrapper
if func.create_only_co:
creation_function = create_co_wrapper
{{
{struct_name} *s = opaque;
+{graph_lock}
s->ret = {name}({ func.gen_list('s->{name}') });
+{graph_unlock}
s->poll_state.in_progress = false;
aio_wait_kick();