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, 5 insertions, 1 deletions

diff --git a/sys/dev/tdfx/tdfx_pci.c b/sys/dev/tdfx/tdfx_pci.c
index 5594a13..cfbfe18 100644
--- a/sys/dev/tdfx/tdfx_pci.c
+++ b/sys/dev/tdfx/tdfx_pci.c
@@ -842,11 +842,15 @@ linux_ioctl_tdfx(struct thread *td, struct linux_ioctl_args* args)
       and one void*. */
    char d_pio[2*sizeof(short) + sizeof(int) + sizeof(void*)];
 
-   struct file *fp = td->td_proc->p_fd->fd_ofiles[args->fd];
+   struct file *fp;
 
+   fp = ffind_hold(td, args->fd);
+   if (fp == NULL)
+	   return (EBADF);
    /* We simply copy the data and send it right to ioctl */
    copyin((caddr_t)args->arg, &d_pio, sizeof(d_pio));
    error = fo_ioctl(fp, cmd, (caddr_t)&d_pio, td);
+   fdrop(fp, td);
    return error;
 }
 #endif /* TDFX_LINUX */