epoch(9): allow preemptible epochs to compose

- Add tracker argument to preemptible epochs
- Inline epoch read path in kernel and tied modules
- Change in_epoch to take an epoch as argument
- Simplify tfb_tcp_do_segment to not take a ti_locked argument,
  there's no longer any benefit to dropping the pcbinfo lock
  and trying to do so just adds an error prone branchfest to
  these functions
- Remove cases of same function recursion on the epoch as
  recursing is no longer free.
- Remove the the TAILQ_ENTRY and epoch_section from struct
  thread as the tracker field is now stack or heap allocated
  as appropriate.

Tested by: pho and Limelight Networks
Reviewed by: kbowling at llnw dot com
Sponsored by: Limelight Networks
Differential Revision: https://reviews.freebsd.org/D16066

1 files changed, 2 insertions, 2 deletions

diff --git a/sys/net/if_gre.h b/sys/net/if_gre.h
index da71fbbf7d50..cc8b08f98396 100644
--- a/sys/net/if_gre.h
+++ b/sys/net/if_gre.h
@@ -91,8 +91,8 @@ MALLOC_DECLARE(M_GRE);
 #endif
 
 #define	GRE2IFP(sc)		((sc)->gre_ifp)
-#define	GRE_RLOCK()		epoch_enter_preempt(net_epoch_preempt)
-#define	GRE_RUNLOCK()		epoch_exit_preempt(net_epoch_preempt)
+#define	GRE_RLOCK()		struct epoch_tracker gre_et; epoch_enter_preempt(net_epoch_preempt, &gre_et)
+#define	GRE_RUNLOCK()		epoch_exit_preempt(net_epoch_preempt, &gre_et)
 #define	GRE_WAIT()		epoch_wait_preempt(net_epoch_preempt)
 
 #define	gre_hdr			gre_uhdr.hdr