Introduce debug.nosleepwithlocks sysctl, 0 by default. If set to 1

and WITNESS is not built, then force all M_WAITOK allocations to
M_NOWAIT behavior (transparently).  This is to be used temporarily
if wierd deadlocks are reported because we still have code paths
that perform M_WAITOK allocations with lock(s) held, which can
lead to deadlock.  If WITNESS is compiled, then the sysctl is ignored
and we ask witness to tell us wether we have locks held, converting
to M_NOWAIT behavior only if it tells us that we do.

Note this removes the previous mbuf.h inclusion as well (only needed
by last revision), and cleans up unneeded [artificial] comparisons
to just the mbuf zones.  The problem described above has nothing to
do with previous mbuf wait behavior; it is a general problem.

1 files changed, 9 insertions, 11 deletions

diff --git a/sys/vm/uma_core.c b/sys/vm/uma_core.c
index 9e1f7d4..4b25a1b 100644
--- a/sys/vm/uma_core.c
+++ b/sys/vm/uma_core.c
@@ -68,7 +68,6 @@ __FBSDID("$FreeBSD$");
 #include <sys/proc.h>
 #include <sys/smp.h>
 #include <sys/vmmeter.h>
-#include <sys/mbuf.h>	/* XXX WITNESS_WARN() hack */
 
 #include <vm/vm.h>
 #include <vm/vm_object.h>
@@ -225,6 +224,9 @@ void uma_print_zone(uma_zone_t);
 void uma_print_stats(void);
 static int sysctl_vm_zone(SYSCTL_HANDLER_ARGS);
 
+static int nosleepwithlocks = 0;
+SYSCTL_INT(_debug, OID_AUTO, nosleepwithlocks, CTLFLAG_RW, &nosleepwithlocks,
+    0, "Convert M_WAITOK to M_NOWAIT to avoid lock-held-across-sleep paths");
 SYSCTL_OID(_vm, OID_AUTO, zone, CTLTYPE_STRING|CTLFLAG_RD,
     NULL, 0, sysctl_vm_zone, "A", "Zone Info");
 SYSINIT(uma_startup3, SI_SUB_VM_CONF, SI_ORDER_SECOND, uma_startup3, NULL);
@@ -1603,7 +1605,7 @@ uma_zalloc_arg(uma_zone_t zone, void *udata, int flags)
 	uma_cache_t cache;
 	uma_bucket_t bucket;
 	int cpu;
-	int badness = 0;
+	int badness;
 
 	/* This is the fast path allocation */
 #ifdef UMA_DEBUG_ALLOC_1
@@ -1613,16 +1615,12 @@ uma_zalloc_arg(uma_zone_t zone, void *udata, int flags)
 	if (!(flags & M_NOWAIT)) {
 		KASSERT(curthread->td_intr_nesting_level == 0,
 		   ("malloc(M_WAITOK) in interrupt context"));
-		if ((zone_mbuf != NULL && zone == zone_mbuf) ||
-		    (zone_clust != NULL && zone == zone_clust) ||
-		    (zone_pack != NULL && zone == zone_pack))
+		badness = nosleepwithlocks;
 #ifdef WITNESS
-			badness = WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK,
-			    NULL,
-			    "malloc(M_WAITOK) of \"%s\", forcing M_NOWAIT",
-			    zone->uz_name);
-#else
-			badness = 1;
+		badness = WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK,
+		    NULL,
+		    "malloc(M_WAITOK) of \"%s\", forcing M_NOWAIT",
+		    zone->uz_name);
 #endif
 		if (badness) {
 			flags &= ~M_WAITOK;