Re: [PATCH v2 2/2] tools/xenstore: simplify xenstored main loop

[Juergen Gross <jgross@suse.com>]

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On 14.05.21 19:05, Julien Grall wrote:
> Hi Juergen,
> 
> On 14/05/2021 12:56, Juergen Gross wrote:
>> The main loop of xenstored is rather complicated due to different
>> handling of socket and ring-page interfaces. Unify that handling by
>> introducing interface type specific functions can_read() and
>> can_write().
>>
>> Signed-off-by: Juergen Gross <jgross@suse.com>
>> ---
>> V2:
>> - split off function vector introduction (Julien Grall)
>> ---
>>   tools/xenstore/xenstored_core.c   | 77 +++++++++++++++----------------
>>   tools/xenstore/xenstored_core.h   |  2 +
>>   tools/xenstore/xenstored_domain.c |  2 +
>>   3 files changed, 41 insertions(+), 40 deletions(-)
>>
>> diff --git a/tools/xenstore/xenstored_core.c 
>> b/tools/xenstore/xenstored_core.c
>> index 856f518075..883a1a582a 100644
>> --- a/tools/xenstore/xenstored_core.c
>> +++ b/tools/xenstore/xenstored_core.c
>> @@ -1659,9 +1659,34 @@ static int readfd(struct connection *conn, void 
>> *data, unsigned int len)
>>       return rc;
>>   }
>> +static bool socket_can_process(struct connection *conn, int mask)
>> +{
>> +    if (conn->pollfd_idx == -1)
>> +        return false;
>> +
>> +    if (fds[conn->pollfd_idx].revents & ~(POLLIN | POLLOUT)) {
>> +        talloc_free(conn);
>> +        return false;
>> +    }
>> +
>> +    return (fds[conn->pollfd_idx].revents & mask) && !conn->is_ignored;
>> +}
>> +
>> +static bool socket_can_write(struct connection *conn)
>> +{
>> +    return socket_can_process(conn, POLLOUT);
>> +}
>> +
>> +static bool socket_can_read(struct connection *conn)
>> +{
>> +    return socket_can_process(conn, POLLIN);
>> +}
>> +
>>   const struct interface_funcs socket_funcs = {
>>       .write = writefd,
>>       .read = readfd,
>> +    .can_write = socket_can_write,
>> +    .can_read = socket_can_read,
>>   };
>>   static void accept_connection(int sock)
>> @@ -2296,47 +2321,19 @@ int main(int argc, char *argv[])
>>               if (&next->list != &connections)
>>                   talloc_increase_ref_count(next);
>> -            if (conn->domain) {
>> -                if (domain_can_read(conn))
>> -                    handle_input(conn);
>> -                if (talloc_free(conn) == 0)
>> -                    continue;
>> -
>> -                talloc_increase_ref_count(conn);
>> -                if (domain_can_write(conn) &&
>> -                    !list_empty(&conn->out_list))
> 
> AFAICT, the check "!list_empty(&conn->out_list)" can be safely removed 
> because write_messages() will check if the list is empty (list_top() 
> returns NULL in this case). Is that correct?

Yes.


Juergen


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