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, 4 insertions, 3 deletions

diff --git a/sys/kern/sys_socket.c b/sys/kern/sys_socket.c
index 04a419a..13f4000 100644
--- a/sys/kern/sys_socket.c
+++ b/sys/kern/sys_socket.c
@@ -197,10 +197,11 @@ soo_close(fp, td)
 	int error = 0;
 	struct socket *so;
 
+	so = (struct socket *)fp->f_data;
 	fp->f_ops = &badfileops;
-	if ((so = (struct socket *)fp->f_data) != NULL) {
-		fp->f_data = NULL;
+	fp->f_data = 0;
+
+	if (so)
 		error = soclose(so);
-	}
 	return (error);
 }