[PATCH v2 2/7] vircommand: Document virCommandSetSendBuffer() behaviour wrt daemonize

[Michal Prívozník]

On 3/23/22 08:48, Marc-André Lureau wrote:
> Hi
> 
> On Tue, Mar 22, 2022 at 8:02 PM Michal Privoznik <mprivozn at redhat.com
> <mailto:mprivozn at redhat.com>> wrote:
> 
>     When virCommandSetSendBuffer() is used over a virCommand that is
>     (or will be) daemonized, then VIR_EXEC_ASYNC_IO the command must
>     have VIR_EXEC_ASYNC_IO flag set no later than at
>     virCommandRunAsync() phase so that the thread that's doing IO is
>     spawned and thus buffers can be sent to the process.
> 
>     Signed-off-by: Michal Privoznik <mprivozn at redhat.com
>     <mailto:mprivozn at redhat.com>>
>     ---
>      src/util/vircommand.c | 3 +++
>      1 file changed, 3 insertions(+)
> 
>     diff --git a/src/util/vircommand.c b/src/util/vircommand.c
>     index 41cf552d7b..5f22bd0ac3 100644
>     --- a/src/util/vircommand.c
>     +++ b/src/util/vircommand.c
>     @@ -1719,6 +1719,9 @@ virCommandFreeSendBuffers(virCommand *cmd)
>       * @buffer is always stolen regardless of the return value. This
>     function
>       * doesn't raise a libvirt error, but rather propagates the error
>     via virCommand.
>       * Thus callers don't need to take a special action if -1 is returned.
>     + *
>     + * When the @cmd is daemonized via virCommandDaemonize() remember
>     to request
>     + * asynchronous IO via virCommandDoAsyncIO().
> 
> 
> Or else the RunAsync() should return an error, no?

Yes.

> 
> Why not call DoAsyncIO() implicitly in RunAsync() in this case?

So what we could do, is to enable VIR_EXEC_ASYNC_IO flag in
virCommandRun() and require explicit call to DoAsyncIO() for
virCommandRunAsync() case. This way, it'll be consistent with the rest
of buffer passing functions, like virCommandSetInputBuffer(),
virCommandSetOutputBuffer() or virCommandSetErrorBuffer().

Would this work for you?

Michal