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.

2 files changed, 6 insertions, 5 deletions

diff --git a/sys/alpha/osf1/osf1_misc.c b/sys/alpha/osf1/osf1_misc.c
index 84526e2..46b20d9 100644
--- a/sys/alpha/osf1/osf1_misc.c
+++ b/sys/alpha/osf1/osf1_misc.c
@@ -667,18 +667,17 @@ osf1_fstat(td, uap)
 	struct thread *td;
 	register struct osf1_fstat_args *uap;
 {
-	register struct filedesc *fdp;
 	register struct file *fp;
 	struct stat ub;
 	struct osf1_stat oub;
 	int error;
 
-	fdp = td->td_proc->p_fd;
-	if ((unsigned)SCARG(uap, fd) >= fdp->fd_nfiles ||
-	    (fp = fdp->fd_ofiles[SCARG(uap, fd)]) == NULL)
+	fp = ffind_hold(td, uap->fd);
+	if (fp == NULL)
 		return (EBADF);
 
 	error = fo_stat(fp, &ub, td);
+	fdrop(fp, td);
 	cvtstat2osf1(&ub, &oub);
 	if (error == 0)
 		error = copyout((caddr_t)&oub, (caddr_t)SCARG(uap, sb),
diff --git a/sys/alpha/osf1/osf1_mount.c b/sys/alpha/osf1/osf1_mount.c
index 2e88b17..4244da3 100644
--- a/sys/alpha/osf1/osf1_mount.c
+++ b/sys/alpha/osf1/osf1_mount.c
@@ -154,7 +154,9 @@ osf1_fstatfs(td, uap)
 		return (error);
 	mp = ((struct vnode *)fp->f_data)->v_mount;
 	sp = &mp->mnt_stat;
-	if ((error = VFS_STATFS(mp, sp, td)))
+	error = VFS_STATFS(mp, sp, td);
+	fdrop(fp, td);
+	if (error)
 		return (error);
 	sp->f_flags = mp->mnt_flag & MNT_VISFLAGMASK;
 	bsd2osf_statfs(sp, &osfs);