Re: [PATCH net v5] vsock/bpf: release sock lock while waiting for data in recvmsg

[Stefano Garzarella <sgarzare@redhat.com>]

On Thu, Nov 12, 2026 at 07:47:11PM +0000, jrmmhm.kernel@eldare.de wrote:
>On Thu, Nov 12, 2026 at 06:23:00PM +0100, Stefano Garzarella wrote:
>>On Mon, Nov 09, 2026 at 09:08:29PM +0100, Jerome Mohm via B4 Relay
>>wrote:
>>>The loop
>>>and the zero-length check belong to the fix (without them the reader
>>>returns early or spins with the lock held), so this is one patch;
>>
>>I don't understand why that fix can't be in a fist patch of the
>>series...
>>
>>>+    if (unlikely(!len || (flags & (MSG_OOB | MSG_ERRQUEUE))))
>>>+        return __vsock_recvmsg(sk, msg, len, flags);
>>
>>... I mean, why this change ^^^ can't be in patch 1/2?
>>
>>BTW I'm not asking to split it (at least for now).
>
>It can: the loop is needed for the deadlock fix, since without it the
>reader returns -EAGAIN early when it wakes without data, but the early
>return isn't. A zero-length read with data in the psock queue already
>spins with the lock held on net, and as far as I can tell from the code
>the early return alone fixes that, plus the MSG_OOB and MSG_ERRQUEUE
>cases. In v4 those reads were patch 2/2. They went into one patch only
>because Alexei's diff replaced both, and my v5 sentence justified that
>badly. You said you're not asking for a split, but since the early
>return isn't needed for the deadlock, it would fit as its own patch:
>should v6 have it as 1/2 and the lock change as 2/2, or stay one patch?

Yeah, I'd prefer 2 patches with this change as first patch.

>
>>I saw some comments from sashiko, can you reply to them?
>
>I'll wait for your answer before sending v6, and I'm replying to the
>Sashiko comments separately.

Great, thanks for that!

Stefano