Messages in this thread | | | Date | Mon, 5 Feb 2018 10:01:32 -0800 (PST) | From | Stefano Stabellini <> | Subject | Re: [PATCH] pvcalls-back: do not return error on inet_accept EAGAIN |
| |
On Sun, 4 Feb 2018, Boris Ostrovsky wrote: > On 02/02/2018 08:34 PM, Stefano Stabellini wrote: > > When the client sends a regular blocking accept request, the backend is > > expected to return only when the accept is completed, simulating a > > blocking behavior, or return an error. > > > > Specifically, on EAGAIN from inet_accept, the backend shouldn't return > > "EAGAIN" to the client. Instead, it should simply continue the wait. > > Otherwise, the client will send another accept request, which will cause > > another EAGAIN to be sent back, which is a waste of resources and not > > conforming to the expected behavior. Change the behavior by turning the > > "goto error" into a return. > > > > Signed-off-by: Stefano Stabellini <stefano@aporeto.com> > > > I am looking at SYSCALL_DEFINE4(accept4) and sock->ops->accept (which *I > think* is inet_accept, at least in some cases) passes all errors (including > EAGAIN) back to the caller. Is this a different case?
Hi Boris,
I didn't explain myself well. You are right that inet_accept passes all errors back to the caller, but this is different: not only it would be a waste of resources to do so, but the different behavior is specified in the PVCalls spec:
"The backend will reply to the request only when a new connection is successfully accepted, i.e. the backend does not return EAGAIN or EWOULDBLOCK."
https://xenbits.xen.org/docs/unstable/misc/pvcalls.html
Look under the "Accept" sub-chapter.
Cheers,
Stefano | |