svn commit: r340413 - in head/sys: kern net sys

[Gleb Smirnoff]

Author: glebius
Date: Tue Nov 13 22:58:38 2018
New Revision: 340413
URL: https://svnweb.freebsd.org/changeset/base/340413

Log:
  For compatibility KPI functions like if_addr_rlock() that used to have
  mutexes but now are converted to epoch(9) use thread-private epoch_tracker.
  Embedding tracker into ifnet(9) or ifnet derived structures creates a non
  reentrable function, that will fail miserably if called simultaneously from
  two different contexts.
  A thread private tracker will provide a single tracker that would allow to
  call these functions safely. It doesn't allow nested call, but this is not
  expected from compatibility KPIs.
  
  Reviewed by:	markj

Modified:
  head/sys/kern/kern_thread.c
  head/sys/kern/subr_epoch.c
  head/sys/net/if.c
  head/sys/net/if_var.h
  head/sys/sys/epoch.h
  head/sys/sys/proc.h

Modified: head/sys/kern/kern_thread.c
==============================================================================
--- head/sys/kern/kern_thread.c	Tue Nov 13 22:41:20 2018	(r340412)
+++ head/sys/kern/kern_thread.c	Tue Nov 13 22:58:38 2018	(r340413)
@@ -272,6 +272,7 @@ thread_init(void *mem, int size, int flags)
 	td->td_rlqe = NULL;
 	EVENTHANDLER_DIRECT_INVOKE(thread_init, td);
 	umtx_thread_init(td);
+	epoch_thread_init(td);
 	td->td_kstack = 0;
 	td->td_sel = NULL;
 	return (0);
@@ -291,6 +292,7 @@ thread_fini(void *mem, int size)
 	turnstile_free(td->td_turnstile);
 	sleepq_free(td->td_sleepqueue);
 	umtx_thread_fini(td);
+	epoch_thread_fini(td);
 	seltdfini(td);
 }
 

Modified: head/sys/kern/subr_epoch.c
==============================================================================
--- head/sys/kern/subr_epoch.c	Tue Nov 13 22:41:20 2018	(r340412)
+++ head/sys/kern/subr_epoch.c	Tue Nov 13 22:58:38 2018	(r340413)
@@ -667,3 +667,17 @@ in_epoch(epoch_t epoch)
 {
 	return (in_epoch_verbose(epoch, 0));
 }
+
+void
+epoch_thread_init(struct thread *td)
+{
+
+	td->td_et = malloc(sizeof(struct epoch_tracker), M_EPOCH, M_WAITOK);
+}
+
+void
+epoch_thread_fini(struct thread *td)
+{
+
+	free(td->td_et, M_EPOCH);
+}

Modified: head/sys/net/if.c
==============================================================================
--- head/sys/net/if.c	Tue Nov 13 22:41:20 2018	(r340412)
+++ head/sys/net/if.c	Tue Nov 13 22:58:38 2018	(r340413)
@@ -1767,35 +1767,29 @@ if_data_copy(struct ifnet *ifp, struct if_data *ifd)
 void
 if_addr_rlock(struct ifnet *ifp)
 {
-	MPASS(*(uint64_t *)&ifp->if_addr_et == 0);
-	epoch_enter_preempt(net_epoch_preempt, &ifp->if_addr_et);
+
+	epoch_enter_preempt(net_epoch_preempt, curthread->td_et);
 }
 
 void
 if_addr_runlock(struct ifnet *ifp)
 {
-	epoch_exit_preempt(net_epoch_preempt, &ifp->if_addr_et);
-#ifdef INVARIANTS
-	bzero(&ifp->if_addr_et, sizeof(struct epoch_tracker));
-#endif
+
+	epoch_exit_preempt(net_epoch_preempt, curthread->td_et);
 }
 
 void
 if_maddr_rlock(if_t ifp)
 {
 
-	MPASS(*(uint64_t *)&ifp->if_maddr_et == 0);
-	epoch_enter_preempt(net_epoch_preempt, &ifp->if_maddr_et);
+	epoch_enter_preempt(net_epoch_preempt, curthread->td_et);
 }
 
 void
 if_maddr_runlock(if_t ifp)
 {
 
-	epoch_exit_preempt(net_epoch_preempt, &ifp->if_maddr_et);
-#ifdef INVARIANTS
-	bzero(&ifp->if_maddr_et, sizeof(struct epoch_tracker));
-#endif
+	epoch_exit_preempt(net_epoch_preempt, curthread->td_et);
 }
 
 /*

Modified: head/sys/net/if_var.h
==============================================================================
--- head/sys/net/if_var.h	Tue Nov 13 22:41:20 2018	(r340412)
+++ head/sys/net/if_var.h	Tue Nov 13 22:58:38 2018	(r340413)
@@ -381,8 +381,6 @@ struct ifnet {
 	 */
 	struct netdump_methods *if_netdump_methods;
 	struct epoch_context	if_epoch_ctx;
-	struct epoch_tracker	if_addr_et;
-	struct epoch_tracker	if_maddr_et;
 
 	/*
 	 * Spare fields to be added before branching a stable branch, so

Modified: head/sys/sys/epoch.h
==============================================================================
--- head/sys/sys/epoch.h	Tue Nov 13 22:41:20 2018	(r340412)
+++ head/sys/sys/epoch.h	Tue Nov 13 22:58:38 2018	(r340413)
@@ -82,5 +82,8 @@ void epoch_exit_preempt(epoch_t epoch, epoch_tracker_t
 void epoch_enter(epoch_t epoch);
 void epoch_exit(epoch_t epoch);
 
+void epoch_thread_init(struct thread *);
+void epoch_thread_fini(struct thread *);
+
 #endif	/* _KERNEL */
 #endif	/* _SYS_EPOCH_H_ */

Modified: head/sys/sys/proc.h
==============================================================================
--- head/sys/sys/proc.h	Tue Nov 13 22:41:20 2018	(r340412)
+++ head/sys/sys/proc.h	Tue Nov 13 22:58:38 2018	(r340413)
@@ -193,6 +193,7 @@ struct trapframe;
 struct turnstile;
 struct vm_map;
 struct vm_map_entry;
+struct epoch_tracker;
 
 /*
  * XXX: Does this belong in resource.h or resourcevar.h instead?
@@ -360,6 +361,7 @@ struct thread {
 	int		td_lastcpu;	/* (t) Last cpu we were on. */
 	int		td_oncpu;	/* (t) Which cpu we are on. */
 	void		*td_lkpi_task;	/* LinuxKPI task struct pointer */
+	struct epoch_tracker *td_et;	/* (k) compat KPI spare tracker */
 	int		td_pmcpend;
 };