314 lines
7.4 KiB
C
314 lines
7.4 KiB
C
/*
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* NET3: Garbage Collector For AF_UNIX sockets
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*
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* Garbage Collector:
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* Copyright (C) Barak A. Pearlmutter.
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* Released under the GPL version 2 or later.
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*
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* Chopped about by Alan Cox 22/3/96 to make it fit the AF_UNIX socket problem.
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* If it doesn't work blame me, it worked when Barak sent it.
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*
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* Assumptions:
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*
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* - object w/ a bit
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* - free list
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*
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* Current optimizations:
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*
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* - explicit stack instead of recursion
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* - tail recurse on first born instead of immediate push/pop
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* - we gather the stuff that should not be killed into tree
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* and stack is just a path from root to the current pointer.
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*
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* Future optimizations:
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*
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* - don't just push entire root set; process in place
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*
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* Fixes:
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* Alan Cox 07 Sept 1997 Vmalloc internal stack as needed.
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* Cope with changing max_files.
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* Al Viro 11 Oct 1998
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* Graph may have cycles. That is, we can send the descriptor
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* of foo to bar and vice versa. Current code chokes on that.
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* Fix: move SCM_RIGHTS ones into the separate list and then
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* skb_free() them all instead of doing explicit fput's.
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* Another problem: since fput() may block somebody may
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* create a new unix_socket when we are in the middle of sweep
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* phase. Fix: revert the logic wrt MARKED. Mark everything
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* upon the beginning and unmark non-junk ones.
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*
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* [12 Oct 1998] AAARGH! New code purges all SCM_RIGHTS
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* sent to connect()'ed but still not accept()'ed sockets.
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* Fixed. Old code had slightly different problem here:
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* extra fput() in situation when we passed the descriptor via
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* such socket and closed it (descriptor). That would happen on
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* each unix_gc() until the accept(). Since the struct file in
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* question would go to the free list and might be reused...
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* That might be the reason of random oopses on filp_close()
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* in unrelated processes.
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*
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* AV 28 Feb 1999
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* Kill the explicit allocation of stack. Now we keep the tree
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* with root in dummy + pointer (gc_current) to one of the nodes.
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* Stack is represented as path from gc_current to dummy. Unmark
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* now means "add to tree". Push == "make it a son of gc_current".
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* Pop == "move gc_current to parent". We keep only pointers to
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* parents (->gc_tree).
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* AV 1 Mar 1999
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* Damn. Added missing check for ->dead in listen queues scanning.
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*
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*/
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#include <linux/kernel.h>
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#include <linux/sched.h>
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#include <linux/string.h>
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#include <linux/socket.h>
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#include <linux/un.h>
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#include <linux/net.h>
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#include <linux/fs.h>
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#include <linux/slab.h>
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#include <linux/skbuff.h>
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#include <linux/netdevice.h>
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#include <linux/file.h>
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#include <linux/proc_fs.h>
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#include <linux/mutex.h>
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#include <net/sock.h>
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#include <net/af_unix.h>
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#include <net/scm.h>
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#include <net/tcp_states.h>
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/* Internal data structures and random procedures: */
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#define GC_HEAD ((struct sock *)(-1))
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#define GC_ORPHAN ((struct sock *)(-3))
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static struct sock *gc_current = GC_HEAD; /* stack of objects to mark */
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atomic_t unix_tot_inflight = ATOMIC_INIT(0);
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static struct sock *unix_get_socket(struct file *filp)
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{
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struct sock *u_sock = NULL;
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struct inode *inode = filp->f_dentry->d_inode;
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/*
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* Socket ?
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*/
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if (S_ISSOCK(inode->i_mode)) {
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struct socket * sock = SOCKET_I(inode);
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struct sock * s = sock->sk;
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/*
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* PF_UNIX ?
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*/
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if (s && sock->ops && sock->ops->family == PF_UNIX)
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u_sock = s;
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}
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return u_sock;
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}
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/*
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* Keep the number of times in flight count for the file
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* descriptor if it is for an AF_UNIX socket.
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*/
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void unix_inflight(struct file *fp)
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{
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struct sock *s = unix_get_socket(fp);
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if(s) {
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atomic_inc(&unix_sk(s)->inflight);
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atomic_inc(&unix_tot_inflight);
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}
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}
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void unix_notinflight(struct file *fp)
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{
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struct sock *s = unix_get_socket(fp);
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if(s) {
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atomic_dec(&unix_sk(s)->inflight);
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atomic_dec(&unix_tot_inflight);
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}
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}
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/*
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* Garbage Collector Support Functions
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*/
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static inline struct sock *pop_stack(void)
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{
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struct sock *p = gc_current;
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gc_current = unix_sk(p)->gc_tree;
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return p;
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}
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static inline int empty_stack(void)
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{
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return gc_current == GC_HEAD;
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}
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static void maybe_unmark_and_push(struct sock *x)
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{
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struct unix_sock *u = unix_sk(x);
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if (u->gc_tree != GC_ORPHAN)
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return;
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sock_hold(x);
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u->gc_tree = gc_current;
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gc_current = x;
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}
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/* The external entry point: unix_gc() */
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void unix_gc(void)
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{
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static DEFINE_MUTEX(unix_gc_sem);
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int i;
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struct sock *s;
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struct sk_buff_head hitlist;
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struct sk_buff *skb;
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/*
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* Avoid a recursive GC.
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*/
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if (!mutex_trylock(&unix_gc_sem))
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return;
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spin_lock(&unix_table_lock);
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forall_unix_sockets(i, s)
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{
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unix_sk(s)->gc_tree = GC_ORPHAN;
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}
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/*
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* Everything is now marked
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*/
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/* Invariant to be maintained:
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- everything unmarked is either:
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-- (a) on the stack, or
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-- (b) has all of its children unmarked
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- everything on the stack is always unmarked
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- nothing is ever pushed onto the stack twice, because:
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-- nothing previously unmarked is ever pushed on the stack
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*/
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/*
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* Push root set
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*/
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forall_unix_sockets(i, s)
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{
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int open_count = 0;
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/*
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* If all instances of the descriptor are not
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* in flight we are in use.
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*
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* Special case: when socket s is embrion, it may be
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* hashed but still not in queue of listening socket.
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* In this case (see unix_create1()) we set artificial
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* negative inflight counter to close race window.
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* It is trick of course and dirty one.
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*/
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if (s->sk_socket && s->sk_socket->file)
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open_count = file_count(s->sk_socket->file);
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if (open_count > atomic_read(&unix_sk(s)->inflight))
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maybe_unmark_and_push(s);
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}
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/*
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* Mark phase
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*/
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while (!empty_stack())
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{
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struct sock *x = pop_stack();
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struct sock *sk;
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spin_lock(&x->sk_receive_queue.lock);
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skb = skb_peek(&x->sk_receive_queue);
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/*
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* Loop through all but first born
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*/
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while (skb && skb != (struct sk_buff *)&x->sk_receive_queue) {
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/*
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* Do we have file descriptors ?
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*/
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if(UNIXCB(skb).fp)
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{
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/*
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* Process the descriptors of this socket
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*/
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int nfd=UNIXCB(skb).fp->count;
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struct file **fp = UNIXCB(skb).fp->fp;
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while(nfd--)
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{
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/*
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* Get the socket the fd matches if
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* it indeed does so
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*/
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if((sk=unix_get_socket(*fp++))!=NULL)
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{
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maybe_unmark_and_push(sk);
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}
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}
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}
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/* We have to scan not-yet-accepted ones too */
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if (x->sk_state == TCP_LISTEN)
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maybe_unmark_and_push(skb->sk);
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skb=skb->next;
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}
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spin_unlock(&x->sk_receive_queue.lock);
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sock_put(x);
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}
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skb_queue_head_init(&hitlist);
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forall_unix_sockets(i, s)
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{
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struct unix_sock *u = unix_sk(s);
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if (u->gc_tree == GC_ORPHAN) {
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struct sk_buff *nextsk;
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spin_lock(&s->sk_receive_queue.lock);
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skb = skb_peek(&s->sk_receive_queue);
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while (skb &&
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skb != (struct sk_buff *)&s->sk_receive_queue) {
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nextsk = skb->next;
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/*
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* Do we have file descriptors ?
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*/
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if (UNIXCB(skb).fp) {
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__skb_unlink(skb,
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&s->sk_receive_queue);
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__skb_queue_tail(&hitlist, skb);
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}
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skb = nextsk;
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}
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spin_unlock(&s->sk_receive_queue.lock);
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}
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u->gc_tree = GC_ORPHAN;
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}
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spin_unlock(&unix_table_lock);
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/*
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* Here we are. Hitlist is filled. Die.
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*/
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__skb_queue_purge(&hitlist);
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mutex_unlock(&unix_gc_sem);
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}
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