net/unix/garbage.c /* * NET3: Garbage Collector For AF_UNIX sockets * * Garbage Collector: * Copyright (C) Barak A. Pearlmutter. * Released under the GPL version 2 or later. * * Chopped about by Alan Cox 22/3/96 to make it fit the AF_UNIX socket problem. * If it doesn't work blame me, it worked when Barak sent it. * * Assumptions: * * - object w/ a bit * - free list * * Current optimizations: * * - explicit stack instead of recursion * - tail recurse on first born instead of immediate push/pop * * Future optimizations: * * - don't just push entire root set; process in place * - use linked list for internal stack * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version * 2 of the License, or (at your option) any later version. * * Fixes: * */ #include <linux/kernel.h> #include <linux/major.h> #include <linux/signal.h> #include <linux/sched.h> #include <linux/errno.h> #include <linux/string.h> #include <linux/stat.h> #include <linux/socket.h> #include <linux/un.h> #include <linux/fcntl.h> #include <linux/termios.h> #include <linux/socket.h> #include <linux/sockios.h> #include <linux/net.h> #include <linux/in.h> #include <linux/fs.h> #include <linux/malloc.h> #include <asm/segment.h> #include <linux/skbuff.h> #include <linux/netdevice.h> #include <net/sock.h> #include <net/tcp.h> #include <net/af_unix.h> #include <linux/proc_fs.h> /* Internal data structures and random procedures: */ #define MAX_STACK 1000 /* Maximum depth of tree (about 1 page) */ static unix_socket **stack; /* stack of objects to mark */ static int in_stack = 0; /* first free entry in stack */ extern inline unix_socket *unix_get_socket(struct file *filp) { unix_socket * u_sock = NULL; struct inode *inode = filp->f_inode; /* * Socket ? */ if (inode && inode->i_sock) { struct socket * s = &inode->u.socket_i; /* * AF_UNIX ? */ if (s->ops == &unix_proto_ops) u_sock = s->data; } return u_sock; } /* * Keep the number of times in flight count for the file * descriptor if it is for an AF_UNIX socket. */ void unix_inflight(struct file *fp) { unix_socket *s=unix_get_socket(fp); if(s) s->protinfo.af_unix.inflight++; } void unix_notinflight(struct file *fp) { unix_socket *s=unix_get_socket(fp); if(s) s->protinfo.af_unix.inflight--; } /* * Garbage Collector Support Functions */ extern inline void push_stack(unix_socket *x) { if (in_stack == MAX_STACK) panic("can't push onto full stack"); stack[in_stack++] = x; } extern inline unix_socket *pop_stack(void) { if (in_stack == 0) panic("can't pop empty gc stack"); return stack[--in_stack]; } extern inline int empty_stack(void) { return in_stack == 0; } extern inline void maybe_mark_and_push(unix_socket *x) { if (x->protinfo.af_unix.marksweep&MARKED) return; x->protinfo.af_unix.marksweep|=MARKED; push_stack(x); } /* The external entry point: unix_gc() */ void unix_gc(void) { static int in_unix_gc=0; unix_socket *s; unix_socket *next; /* * Avoid a recursive GC. */ if(in_unix_gc) return; in_unix_gc=1; stack=(unix_socket **)get_free_page(GFP_KERNEL); /* * Assume everything is now unmarked */ /* Invariant to be maintained: - everything marked is either: -- (a) on the stack, or -- (b) has all of its children marked - everything on the stack is always marked - nothing is ever pushed onto the stack twice, because: -- nothing previously marked is ever pushed on the stack */ /* * Push root set */ for(s=unix_socket_list;s!=NULL;s=s->next) { /* * If all instances of the descriptor are not * in flight we are in use. */ if(s->socket && s->socket->file && s->socket->file->f_count > s->protinfo.af_unix.inflight) maybe_mark_and_push(s); } /* * Mark phase */ while (!empty_stack()) { unix_socket *x = pop_stack(); unix_socket *f=NULL,*sk; struct sk_buff *skb; tail: skb=skb_peek(&x->receive_queue); /* * Loop through all but first born */ while(skb && skb != (struct sk_buff *)&x->receive_queue) { /* * Do we have file descriptors ? */ if(skb->h.filp) { /* * Process the descriptors of this socket */ int nfd=*(int *)skb->h.filp; struct file **fp=(struct file **)(skb->h.filp+sizeof(int)); while(nfd--) { /* * Get the socket the fd matches if * it indeed does so */ if((sk=unix_get_socket(*fp++))!=NULL) { /* * Remember the first, mark the * rest. */ if(f==NULL) f=sk; else maybe_mark_and_push(sk); } } } skb=skb->next; } /* * Handle first born specially */ if (f) { if (!(f->protinfo.af_unix.marksweep&MARKED)) { f->protinfo.af_unix.marksweep|=MARKED; x=f; f=NULL; goto tail; } } } /* * Sweep phase. NOTE: this part dominates the time complexity */ for(s=unix_socket_list;s!=NULL;s=next) { next=s->next; if (!(s->protinfo.af_unix.marksweep&MARKED)) { /* * We exist only in the passing tree of sockets * that is no longer connected to active descriptors * Time to die.. * * Subtle item: We will correctly sweep out the * socket that has just been closed by the user. * We must not close this as we are in the middle * of its close at this moment. Skip that file * using f_count==0 to spot it. */ if(s->socket && s->socket->file && s->socket->file->f_count) close_fp(s->socket->file); } else s->protinfo.af_unix.marksweep&=~MARKED; /* unmark everything for next collection */ } in_unix_gc=0; free_page((long)stack); }