Re: uma_zalloc_arg: zone "256" with non-sleepable exclusive rw ifnet_rw @ /usr/src/sys/net/if.c:414

On Monday, January 17, 2011 12:55:26 pm Sergey Kandaurov wrote:
> Hi,
> 
> I see this "malloc with non-sleepable" on current during boot.
> It's strange that I don't see it if I boot via pxe/nfs.
> 
> if_alloc() calls ifindex_alloc_locked() under IFNET_WLOCK() which
> might call if_grow().
> Looks like a regression from r196553.

I'm guessing that ifindex_alloc() should drop the lock and retry the 
allocation after calling if_grow()?  This compiles, but I haven't booted it 
yet:

Index: if.c
===================================================================
--- if.c	(revision 217400)
+++ if.c	(working copy)
_at__at_ -266,6 +266,7 _at__at_ ifindex_alloc_locked(u_short *idxp)
 
 	IFNET_WLOCK_ASSERT();
 
+retry:
 	/*
 	 * Try to find an empty slot below V_if_index.  If we fail, take the
 	 * next slot.
_at__at_ -278,10 +279,11 _at__at_ ifindex_alloc_locked(u_short *idxp)
 	/* Catch if_index overflow. */
 	if (idx < 1)
 		return (ENOSPC);
-	if (idx > V_if_index)
-		V_if_index = idx;
-	if (V_if_index >= V_if_indexlim)
+	if (idx > V_if_index) {
 		if_grow();
+		goto retry;
+	}
+	V_if_index = idx;
 	*idxp = idx;
 	return (0);
 }
_at__at_ -385,16 +387,25 _at__at_ VNET_SYSUNINIT(vnet_if_uninit, SI_SUB_INIT_IF, SI_
 static void
 if_grow(void)
 {
+	int oldlim;
 	u_int n;
 	struct ifindex_entry *e;
 
-	V_if_indexlim <<= 1;
-	n = V_if_indexlim * sizeof(*e);
+	IFNET_WLOCK_ASSERT();
+	oldlim = V_if_indexlim;
+	IFNET_WUNLOCK();
+	n = (oldlim << 1) * sizeof(*e);
 	e = malloc(n, M_IFNET, M_WAITOK | M_ZERO);
+	IFNET_WLOCK();
+	if (V_if_indexlim != oldlim) {
+		free(e, M_IFNET);
+		return;
+	}
 	if (V_ifindex_table != NULL) {
 		memcpy((caddr_t)e, (caddr_t)V_ifindex_table, n/2);
 		free((caddr_t)V_ifindex_table, M_IFNET);
 	}
+	V_if_indexlim <<= 1;
 	V_ifindex_table = e;
 }
 

-- 
John Baldwin