SMP Lock struct file, filedesc and the global file list.

Seigo Tanimura (tanimura) posted the initial delta.

I've polished it quite a bit reducing the need for locking and
adapting it for KSE.

Locks:

1 mutex in each filedesc
   protects all the fields.
   protects "struct file" initialization, while a struct file
     is being changed from &badfileops -> &pipeops or something
     the filedesc should be locked.

1 mutex in each struct file
   protects the refcount fields.
   doesn't protect anything else.
   the flags used for garbage collection have been moved to
     f_gcflag which was the FILLER short, this doesn't need
     locking because the garbage collection is a single threaded
     container.
  could likely be made to use a pool mutex.

1 sx lock for the global filelist.

struct file *	fhold(struct file *fp);
        /* increments reference count on a file */

struct file *	fhold_locked(struct file *fp);
        /* like fhold but expects file to locked */

struct file *	ffind_hold(struct thread *, int fd);
        /* finds the struct file in thread, adds one reference and
                returns it unlocked */

struct file *	ffind_lock(struct thread *, int fd);
        /* ffind_hold, but returns file locked */

I still have to smp-safe the fget cruft, I'll get to that asap.

1 files changed, 5 insertions, 4 deletions

diff --git a/sys/netgraph/ng_socket.c b/sys/netgraph/ng_socket.c
index f34fa7f..09ce2cf 100644
--- a/sys/netgraph/ng_socket.c
+++ b/sys/netgraph/ng_socket.c
@@ -569,7 +569,6 @@ ng_detach_common(struct ngpcb *pcbp, int which)
 static int
 ng_internalize(struct mbuf *control, struct thread *td)
 {
-	struct filedesc *fdp = td->td_proc->p_fd;
 	struct cmsghdr *cm = mtod(control, struct cmsghdr *);
 	struct file *fp;
 	struct vnode *vn;
@@ -592,10 +591,9 @@ ng_internalize(struct mbuf *control, struct thread *td)
 	/* Check that the FD given is legit. and change it to a pointer to a
 	 * struct file. */
 	fd = CMSG_DATA(cm);
-	if ((unsigned) fd >= fdp->fd_nfiles
-	    || (fp = fdp->fd_ofiles[fd]) == NULL) {
+	fp = ffind_hold(td, fd);
+	if (fp == NULL)
 		return (EBADF);
-	}
 
 	/* Depending on what kind of resource it is, act differently. For
 	 * devices, we treat it as a file. For a AF_NETGRAPH socket,
@@ -609,14 +607,17 @@ ng_internalize(struct mbuf *control, struct thread *td)
 			/* XXX then what :) */
 			/* how to pass on to other modules? */
 		} else {
+			fdrop(fp, td);
 			TRAP_ERROR;
 			return (EINVAL);
 		}
 		break;
 	default:
+		fdrop(fp, td);
 		TRAP_ERROR;
 		return (EINVAL);
 	}
+	fdrop(fp, td);
 	return (0);
 }
 #endif	/* NOTYET */