Re: [PATCH 7/8] hw/9pfs: annotate V9fsTransport callbacks as coroutine_fn

[Philippe Mathieu-Daudé]

On 20/7/26 16:02, Christian Schoenebeck wrote:

On Monday, 20 July 2026 09:55:36 CEST Marc-André Lureau wrote:

All V9fsTransport callbacks are invoked exclusively from coroutine
context (the v9fs_* PDU handlers). Annotate the function pointer
types in V9fsTransport and all implementations (virtio and xen
backends), as well as intermediate callers in 9p.c (pdu_marshal,
pdu_unmarshal, v9fs_init_qiov_from_pdu, etc.).

Signed-off-by: Marc-André Lureau <marcandre.lur...@redhat.com>
---
  hw/9pfs/9p.h               | 26 +++++++++++++++-----------
  hw/9pfs/9p.c               | 31 +++++++++++++++++++------------
  hw/9pfs/virtio-9p-device.c | 24 +++++++++++++-----------
  hw/9pfs/xen-9p-backend.c   | 34 +++++++++++++++++-----------------
  4 files changed, 64 insertions(+), 51 deletions(-)

diff --git a/hw/9pfs/9p.h b/hw/9pfs/9p.h
index 1a309664f6e..0e52ffbdf38 100644
--- a/hw/9pfs/9p.h
+++ b/hw/9pfs/9p.h
@@ -472,17 +472,21 @@ void pdu_submit(V9fsPDU *pdu, P9MsgHeader *hdr);
  void v9fs_reset(V9fsState *s);


  struct V9fsTransport {
-    ssize_t     (*pdu_vmarshal)(V9fsPDU *pdu, size_t offset, const char *fmt,
-                                va_list ap);
-    ssize_t     (*pdu_vunmarshal)(V9fsPDU *pdu, size_t offset, const char *fmt,
-                                  va_list ap);
-    void        (*init_in_iov_from_pdu)(V9fsPDU *pdu, struct iovec **piov,
-                                        unsigned int *pniov, size_t size);
-    void        (*init_out_iov_from_pdu)(V9fsPDU *pdu, struct iovec **piov,
-                                         unsigned int *pniov, size_t size);
-    void        (*push_and_notify)(V9fsPDU *pdu);
-    size_t      (*msize_limit)(V9fsState *s);
-    size_t      (*response_buffer_size)(V9fsPDU *pdu);
+    ssize_t     coroutine_fn (*pdu_vmarshal)(V9fsPDU *pdu, size_t offset,
+                                             const char *fmt, va_list ap);
+    ssize_t     coroutine_fn (*pdu_vunmarshal)(V9fsPDU *pdu, size_t offset,
+                                               const char *fmt, va_list ap);
+    void        coroutine_fn (*init_in_iov_from_pdu)(V9fsPDU *pdu,
+                                                     struct iovec **piov,
+                                                     unsigned int *pniov,
+                                                     size_t size);
+    void        coroutine_fn (*init_out_iov_from_pdu)(V9fsPDU *pdu,
+                                                      struct iovec **piov,
+                                                      unsigned int *pniov,
+                                                      size_t size);
+    void        coroutine_fn (*push_and_notify)(V9fsPDU *pdu);
+    size_t      coroutine_fn (*msize_limit)(V9fsState *s);
+    size_t      coroutine_fn (*response_buffer_size)(V9fsPDU *pdu);
  };

I wonder whether that could be made more diff/blame-friendly. Especially as
this currently only serves documentation purposes.

They way you are positioning coroutine_fn it usually resolves to an attribute
attached to the function's return type, not to the function itself, even
though clang/gcc handling it flexible. For attaching an attribute to the
function itself the attribute should either be attached before the function
declaration or after the function declaration.

I tend to aggree it would be clearer to have these attributes /before/
the function prototype declaration.

In both cases you could then
add it to its own, separate line, avoiding a lot of noise.

/Christian