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, 3 insertions, 1 deletions

diff --git a/sys/i386/ibcs2/ibcs2_stat.c b/sys/i386/ibcs2/ibcs2_stat.c
index fd39853..148da17 100644
--- a/sys/i386/ibcs2/ibcs2_stat.c
+++ b/sys/i386/ibcs2/ibcs2_stat.c
@@ -133,7 +133,9 @@ ibcs2_fstatfs(td, uap)
 		return (error);
 	mp = ((struct vnode *)fp->f_data)->v_mount;
 	sp = &mp->mnt_stat;
-	if ((error = VFS_STATFS(mp, sp, td)) != 0)
+	error = VFS_STATFS(mp, sp, td);
+	fdrop(fp, td);
+	if (error != 0)
 		return (error);
 	sp->f_flags = mp->mnt_flag & MNT_VISFLAGMASK;
 	return cvt_statfs(sp, (caddr_t)SCARG(uap, buf), SCARG(uap, len));