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, 2 deletions

diff --git a/sys/sys/fcntl.h b/sys/sys/fcntl.h
index 85a168c..bec6e5d 100644
--- a/sys/sys/fcntl.h
+++ b/sys/sys/fcntl.h
@@ -90,8 +90,9 @@
 #define	O_TRUNC		0x0400		/* truncate to zero length */
 #define	O_EXCL		0x0800		/* error if already exists */
 #ifdef _KERNEL
-#define	FMARK		0x1000		/* mark during gc() */
-#define	FDEFER		0x2000		/* defer for next gc pass */
+/* FMARK/FDEFER kept in f_gcflags */
+#define	FMARK		0x1		/* mark during gc() */
+#define	FDEFER		0x2		/* defer for next gc pass */
 #define	FHASLOCK	0x4000		/* descriptor holds advisory lock */
 #endif