Re: [PATCH] osdep.h: Add doc comment for qemu_get_thread_id()

[Eric Blake]

On 7/16/20 10:41 AM, Peter Maydell wrote:
> Add a documentation comment for qemu_get_thread_id(): since this
> is rather host-OS-specific it's useful if people writing the
> implementation and people thinking of using the function know
> what the purpose and limitations are.
>
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
> Based on conversation with Dan on IRC, and prompted by the recent
> patch to add OpenBSD support.
>
> Q: should we document exactly what the thread-id value is for
> each host platform in the QMP documentation ? Somebody writing
> a management layer app should ideally not have to grovel through
> the application to figure out what they should do with the
> integer value they get back from query-cpus...
>
>   include/qemu/osdep.h | 14 ++++++++++++++
>   1 file changed, 14 insertions(+)

Do we need a counterpart change...

> diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
> index 4841b5c6b5f..8279f72e5ed 100644
> --- a/include/qemu/osdep.h
> +++ b/include/qemu/osdep.h
> @@ -515,6 +515,20 @@ bool qemu_has_ofd_lock(void);
>   
>   bool qemu_write_pidfile(const char *pidfile, Error **errp);
>   
> +/**
> + * qemu_get_thread_id: Return OS-specific ID of current thread
> + *
> + * This function returns an OS-specific identifier of the
> + * current thread. This will be used for the "thread-id" field in
> + * the response to the QMP query-cpus and query-iothreads commands.

...to the qapi definition of query-cpus and query-iothreads?

> + * The intention is that a VM management layer application can then
> + * use it to tie specific QEMU vCPU and IO threads to specific host
> + * CPUs using whatever the host OS's CPU affinity setting API is.
> + * New implementations of this function for new host OSes should
> + * return the most sensible integer ID that works for that purpose.
> + *
> + * This function should not be used for anything else inside QEMU.
> + */
>   int qemu_get_thread_id(void);

Otherwise this change looks sensible to me.

Reviewed-by: Eric Blake <eblake@redhat.com>

>   
>   #ifndef CONFIG_IOVEC

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org