Add a new kind of reference count (fd_holdcnt) to struct filedesc

which holds on to just the data structure and the mutex.  (The
existing refcount (fd_refcnt) holds onto the open files in the
descriptor.)

The fd_holdcnt is protected by fdesc_mtx, fd_refcnt by FILEDESC_LOCK.

Add fdhold(struct proc *) which gets a hold on the filedescriptors of
the specified proc..

Add fddrop(struct filedesc *) which drops the fd_holdcnt and if zero
destroys the mutex and frees the memory.

Initialize the fd_holdcnt to one in fdinit().  Normal operations on
the filedesc structure will not change it.

In fdfree() use fddrop() to dispose of the mutex and structure.  Hold
the FILEDESC_LOCK() until we have cleaned out the contents and carefully
set the fields to null values during cleanup.

Use fdhold()/fddrop() in mountcheckdirs() and sysctl_kern_file().

0 files changed, 0 insertions, 0 deletions