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, 7 insertions, 2 deletions

diff --git a/sys/dev/aac/aac.c b/sys/dev/aac/aac.c
index 42e3697..f456f3f 100644
--- a/sys/dev/aac/aac.c
+++ b/sys/dev/aac/aac.c
@@ -2576,16 +2576,21 @@ aac_linux_ioctl(struct thread *td, struct linux_ioctl_args *args)
 {
 	struct file *fp;
 	u_long cmd;
+	int error;
 
 	debug_called(2);
 
-	fp = td->td_proc->p_fd->fd_ofiles[args->fd];
+	fp = ffind_hold(td, args->fd);
+	if (fp == NULL)
+		return (EBADF);
 	cmd = args->cmd;
 
 	/*
 	 * Pass the ioctl off to our standard handler.
 	 */
-	return(fo_ioctl(fp, cmd, (caddr_t)args->arg, td));
+	error = (fo_ioctl(fp, cmd, (caddr_t)args->arg, td));
+	fdrop(fp, td);
+	return (error);
 }
 
 #endif