Add a new network interface flag, IFF_NEEDSGIANT, which will allow

device drivers to declare that the ifp->if_start() method implemented
by the driver requires Giant in order to operate correctly.

Add a 'struct task' to 'struct ifnet' that can be used to execute a
deferred ifp->if_start() in the event that if_start needs to be called
in a Giant-free environment.  To do this, introduce if_start(), a
wrapper function for ifp->if_start().  If the interface can run MPSAFE,
it directly dispatches into the interface start routine.  If it can't
run MPSAFE, we're running with debug.mpsafenet != 0, and Giant isn't
currently held, the task is queued to execute in a swi holding Giant
via if_start_deferred().

Modify if_handoff() to use if_start() instead of direct dispatch.
Modify 802.11 to use if_start() instead of direct dispatch.

This is intended to provide increased compatibility for non-MPSAFE
network device drivers in the presence of Giant-free operation via
asynchronous dispatch.  However, this commit does not mark any network
interfaces as IFF_NEEDSGIANT.

2 files changed, 2 insertions, 2 deletions

diff --git a/sys/net80211/ieee80211_output.c b/sys/net80211/ieee80211_output.c
index 3e144458..b08fff0 100644
--- a/sys/net80211/ieee80211_output.c
+++ b/sys/net80211/ieee80211_output.c
@@ -130,7 +130,7 @@ ieee80211_mgmt_output(struct ifnet *ifp, struct ieee80211_node *ni,
 
 	IF_ENQUEUE(&ic->ic_mgtq, m);
 	ifp->if_timer = 1;
-	(*ifp->if_start)(ifp);
+	if_start(ifp);
 	return 0;
 }
 
diff --git a/sys/net80211/ieee80211_proto.c b/sys/net80211/ieee80211_proto.c
index 899fded..1f4301a 100644
--- a/sys/net80211/ieee80211_proto.c
+++ b/sys/net80211/ieee80211_proto.c
@@ -513,7 +513,7 @@ ieee80211_newstate(struct ieee80211com *ic, enum ieee80211_state nstate, int mgt
 					IEEE80211_RATE2MBS(ni->ni_rates.rs_rates[ni->ni_txrate]));
 			}
 			ic->ic_mgt_timer = 0;
-			(*ifp->if_start)(ifp);
+			if_start(ifp);
 			break;
 		}
 		break;