Re: [Libguestfs] [PATCH libnbd] lib: Remove cookie parameter from completion callbacks.
On 7/30/19 10:36 AM, Richard W.M. Jones wrote:
As discussed in this thread, the parameter is an invitation to write
code with race conditions:
https://www.redhat.com/archives/libguestfs/2019-July/thread.html#00309
---
+++ b/generator/generator
@@ -1729,7 +1729,7 @@ C<nbd_pread>.";
default_call with
args = [ BytesPersistOut ("buf", "count"); UInt64
"offset";
Closure { cbname="callback";
- cbargs=[Int64 "cookie"; Mutable (Int
"error")] };
+ cbargs=[Mutable (Int "error")] };
No trailing ; in cbargs=[]...
@@ -1773,8 +1776,7 @@ documented in
C<nbd_pread_structured>.";
UInt "status";
Mutable (Int "error"); ]};
Closure { cbname="callback";
- cbargs=[Int64 "cookie";
- Mutable (Int "error"); ]};
+ cbargs=[Mutable (Int "error"); ]};
...but there is here. Pre-existing, and OCaml tolerates our
inconsistency, but it's probably nicer to uniformly skip the trailing ;.
Flags "flags" ];
ret = RInt64;
permitted_states = [ Connected ];
@@ -1782,8 +1784,11 @@ documented in C<nbd_pread_structured>.";
longdesc = "\
Issue a read command to the NBD server. This returns the
unique positive 64 bit cookie for this command, or C<-1> on
-error. If this command returns a cookie, then C<callback>
+error.
+
+When the command completes, C<callback>
will be invoked as described in L<libnbd(3)/Completion callbacks>.
+
Do we need wording anywhere (probably in the .pod, so we only state it
once) that mentions that the callback routine is not invoked if
nbd_aio_FOO_callback returns -1?
ACK.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
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