Remove NETISR_MPSAFE, which allows specific netisr handlers to be directly

dispatched without Giant, and add NETISR_FORCEQUEUE, which allows specific
netisr handlers to always be dispatched via a queue (deferred).  Mark the
usb and if_ppp netisr handlers as NETISR_FORCEQUEUE, and explicitly
acquire Giant in those handlers.

Previously, any netisr handler not marked NETISR_MPSAFE would necessarily
run deferred and with Giant acquired.  This change removes Giant
scaffolding from the netisr infrastructure, but NETISR_FORCEQUEUE allows
non-MPSAFE handlers to continue to force deferred dispatch so as to avoid
lock order reversals between their acqusition of Giant and any calling
context.

It is likely we will be able to remove NETISR_FORCEQUEUE once
IFF_NEEDSGIANT is removed, as non-MPSAFE usb and if_ppp drivers will no
longer be supported.

Reviewed by:	bz
MFC after:	1 month
X-MFC note:	We can't remove NETISR_MPSAFE from stable/7 for KPI reasons,
		but the rest can go back.

1 files changed, 1 insertions, 1 deletions

diff --git a/sys/net/netisr.h b/sys/net/netisr.h
index 1fb411c..d5bd8e7 100644
--- a/sys/net/netisr.h
+++ b/sys/net/netisr.h
@@ -83,7 +83,7 @@ typedef void netisr_t (struct mbuf *);
   
 void	netisr_dispatch(int, struct mbuf *);
 int	netisr_queue(int, struct mbuf *);
-#define	NETISR_MPSAFE	0x0001		/* ISR does not need Giant */
+#define	NETISR_FORCEQUEUE	0x0002		/* Force queued dispatch. */
 void	netisr_register(int, netisr_t *, struct ifqueue *, int);
 void	netisr_unregister(int);