git: ec0c098369c8 - stable/14 - Hyper-V: hn: rewrite hn rsc swtich to avoid sysctl hang

The branch stable/14 has been updated by whu:

URL: https://cgit.FreeBSD.org/src/commit/?id=ec0c098369c8fb1acbe0b0566769dd8b98d75753

commit ec0c098369c8fb1acbe0b0566769dd8b98d75753
Author:     Wei Hu <whu@FreeBSD.org>
AuthorDate: 2025-02-04 13:39:14 +0000
Commit:     Wei Hu <whu@FreeBSD.org>
CommitDate: 2025-03-12 08:18:01 +0000

    Hyper-V: hn: rewrite hn rsc swtich to avoid sysctl hang
    
    Changing the rsc_switch flag using sysctl to turn rsc on or off
    could hang. The orignal code sends request to host to get the
    mtu setting. Sometimes the host fails to reply, causing
    the thread to sleep forever waiting for the host response.
    
    Use existing cached mtu from hn device instead to avoid calling
    host.
    
    Reported by:    whu
    Tested by:      whu
    MFC after:      1 week
    
    (cherry picked from commit da1deb784d9ad3a4015a3f91fa1a5ce394fd3fdb)
---
 sys/dev/hyperv/netvsc/if_hn.c | 30 ++++++++++++++----------------
 1 file changed, 14 insertions(+), 16 deletions(-)

diff --git a/sys/dev/hyperv/netvsc/if_hn.c b/sys/dev/hyperv/netvsc/if_hn.c
index 9f51f5b32199..db5ebdfd65bc 100644
--- a/sys/dev/hyperv/netvsc/if_hn.c
+++ b/sys/dev/hyperv/netvsc/if_hn.c
@@ -2355,7 +2355,7 @@ hn_attach(device_t dev)
 	}
 
 	SYSCTL_ADD_PROC(ctx, child, OID_AUTO, "rsc_switch",
-	    CTLTYPE_UINT | CTLFLAG_RW, sc, 0, hn_rsc_sysctl, "A",
+	    CTLTYPE_UINT | CTLFLAG_RW, sc, 0, hn_rsc_sysctl, "I",
 	    "switch to rsc");
 
 	/*
@@ -4523,24 +4523,22 @@ static int
 hn_rsc_sysctl(SYSCTL_HANDLER_ARGS)
 {
 	struct hn_softc *sc = arg1;
-	uint32_t mtu;
+	int rsc_ctrl, mtu;
 	int error;
-	HN_LOCK(sc);
-	error = hn_rndis_get_mtu(sc, &mtu);
-	if (error) {
-		if_printf(sc->hn_ifp, "failed to get mtu\n");
-		goto back;
-	}
-	error = SYSCTL_OUT(req, &(sc->hn_rsc_ctrl), sizeof(sc->hn_rsc_ctrl));
+
+	rsc_ctrl = sc->hn_rsc_ctrl;
+	error = sysctl_handle_int(oidp, &rsc_ctrl, 0, req);
 	if (error || req->newptr == NULL)
-		goto back;
+		return (error);
+
+	if (sc->hn_rsc_ctrl != rsc_ctrl) {
+		HN_LOCK(sc);
+		sc->hn_rsc_ctrl = rsc_ctrl;
+		mtu = if_getmtu(sc->hn_ifp);
+		error = hn_rndis_reconf_offload(sc, mtu);
+		HN_UNLOCK(sc);
+	}
 
-	error = SYSCTL_IN(req, &(sc->hn_rsc_ctrl), sizeof(sc->hn_rsc_ctrl));
-	if (error)
-		goto back;
-	error = hn_rndis_reconf_offload(sc, mtu);
-back:
-	HN_UNLOCK(sc);
 	return (error);
 }
 #ifndef RSS