Don't grab Giant in crfree(), since prison_free() no longer requires it.

The uidinfo code appears to be MPSAFE, and is referenced without Giant
elsewhere.  While this grab of Giant was only made in fairly rare
circumstances (actually GC'ing on refcount==0), grabbing Giant here
potentially introduces lock order issues with any locks held by the
caller.  So this probably won't help performance much unless you change
credentials a lot in an application, and leave a lot of file descriptors
and cached credentials around.  However, it simplifies locking down
consumers of the credential interfaces.

Bumped into by:	sam
Appeased:	tjr

1 files changed, 1 insertions, 3 deletions

diff --git a/sys/kern/kern_prot.c b/sys/kern/kern_prot.c
index d6ecb3f..1d8f07e 100644
--- a/sys/kern/kern_prot.c
+++ b/sys/kern/kern_prot.c
@@ -1746,13 +1746,12 @@ crfree(struct ucred *cr)
 	mtx_lock(mtxp);
 	KASSERT(cr->cr_ref > 0, ("bad ucred refcount: %d", cr->cr_ref));
 	if (--cr->cr_ref == 0) {
+		mtx_unlock(mtxp);
 		/*
 		 * Some callers of crget(), such as nfs_statfs(),
 		 * allocate a temporary credential, but don't
 		 * allocate a uidinfo structure.
 		 */
-		mtx_unlock(mtxp);
-		mtx_lock(&Giant);
 		if (cr->cr_uidinfo != NULL)
 			uifree(cr->cr_uidinfo);
 		if (cr->cr_ruidinfo != NULL)
@@ -1766,7 +1765,6 @@ crfree(struct ucred *cr)
 		mac_destroy_cred(cr);
 #endif
 		FREE(cr, M_CRED);
-		mtx_unlock(&Giant);
 	} else {
 		mtx_unlock(mtxp);
 	}