Push down Giant inside sysctl. Also add some more assertions to the code.

In the existing code we didn't really enforce that callers hold Giant
before calling userland_sysctl(), even though there is no guarantee it
is safe. Fix this by just placing Giant locks around the call to the oid
handler. This also means we only pick up Giant for a very short period
of time. Maybe we should add MPSAFE flags to sysctl or phase it out all
together.

I've also added SYSCTL_LOCK_ASSERT(). We have to make sure sysctl_root()
and name2oid() are called with the sysctl lock held.

Reviewed by:	Jille Timmermans <jille quis cx>

1 files changed, 2 insertions, 6 deletions

diff --git a/sys/i386/ibcs2/ibcs2_sysi86.c b/sys/i386/ibcs2/ibcs2_sysi86.c
index 4d76218..12d5c4a 100644
--- a/sys/i386/ibcs2/ibcs2_sysi86.c
+++ b/sys/i386/ibcs2/ibcs2_sysi86.c
@@ -74,15 +74,11 @@ ibcs2_sysi86(struct thread *td, struct ibcs2_sysi86_args *args)
 
 	case SETNAME:  {  /* set hostname given string w/ len <= 7 chars */
 	        int name[2];
-	        int error;
 
 		name[0] = CTL_KERN;
 		name[1] = KERN_HOSTNAME;
-		mtx_lock(&Giant);
-		error = userland_sysctl(td, name, 2, 0, 0, 0, 
-		    args->arg, 7, 0, 0);
-		mtx_unlock(&Giant);
-		return (error);
+		return (userland_sysctl(td, name, 2, 0, 0, 0, 
+		    args->arg, 7, 0, 0));
 	}
 
 	case SI86_MEM:	/* size of physical memory */