/* * JFFS2 -- Journalling Flash File System, Version 2. * * Copyright © 2001-2007 Red Hat, Inc. * Copyright © 2004-2010 David Woodhouse <dwmw2@infradead.org> * * Created by David Woodhouse <dwmw2@infradead.org> * * For licensing information, see the file 'LICENCE' in this directory. * */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include <linux/kernel.h>#include <linux/jffs2.h>#include <linux/mtd/mtd.h>#include <linux/completion.h>#include <linux/sched/signal.h>#include <linux/freezer.h>#include <linux/kthread.h>#include "nodelist.h"  static int jffs2_garbage_collect_thread(void *); void jffs2_garbage_collect_trigger(struct jffs2_sb_info *c){	assert_spin_locked(&c->erase_completion_lock);	if (c->gc_task && jffs2_thread_should_wake(c))		send_sig(SIGHUP, c->gc_task, 1);} /* This must only ever be called when no GC thread is currently running */int jffs2_start_garbage_collect_thread(struct jffs2_sb_info *c){	struct task_struct *tsk;	int ret = 0; 	BUG_ON(c->gc_task); 	init_completion(&c->gc_thread_start);	init_completion(&c->gc_thread_exit); 	tsk = kthread_run(jffs2_garbage_collect_thread, c, "jffs2_gcd_mtd%d", c->mtd->index);	if (IS_ERR(tsk)) {		pr_warn("fork failed for JFFS2 garbage collect thread: %pe\n",			tsk);		complete(&c->gc_thread_exit);		ret = PTR_ERR(tsk);	} else {		/* Wait for it... */		jffs2_dbg(1, "Garbage collect thread is pid %d\n", tsk->pid);		wait_for_completion(&c->gc_thread_start);		ret = tsk->pid;	} 	return ret;} void jffs2_stop_garbage_collect_thread(struct jffs2_sb_info *c){	int wait = 0;	spin_lock(&c->erase_completion_lock);	if (c->gc_task) {		jffs2_dbg(1, "Killing GC task %d\n", c->gc_task->pid);		send_sig(SIGKILL, c->gc_task, 1);		wait = 1;	}	spin_unlock(&c->erase_completion_lock);	if (wait)		wait_for_completion(&c->gc_thread_exit);} static int jffs2_garbage_collect_thread(void *_c){	struct jffs2_sb_info *c = _c;	sigset_t hupmask; 	siginitset(&hupmask, sigmask(SIGHUP));	allow_signal(SIGKILL);	allow_signal(SIGSTOP);	allow_signal(SIGHUP); 	c->gc_task = current;	complete(&c->gc_thread_start); 	set_user_nice(current, 10); 	set_freezable();	for (;;) {		sigprocmask(SIG_UNBLOCK, &hupmask, NULL);	again:		spin_lock(&c->erase_completion_lock);		if (!jffs2_thread_should_wake(c)) {			set_current_state (TASK_INTERRUPTIBLE);			spin_unlock(&c->erase_completion_lock);			jffs2_dbg(1, "%s(): sleeping...\n", __func__);			schedule();		} else {			spin_unlock(&c->erase_completion_lock);		}		/* Problem - immediately after bootup, the GCD spends a lot		 * of time in places like jffs2_kill_fragtree(); so much so		 * that userspace processes (like gdm and X) are starved		 * despite plenty of cond_resched()s and renicing.  Yield()		 * doesn't help, either (presumably because userspace and GCD		 * are generally competing for a higher latency resource -		 * disk).		 * This forces the GCD to slow the hell down.   Pulling an		 * inode in with read_inode() is much preferable to having		 * the GC thread get there first. */		schedule_timeout_interruptible(msecs_to_jiffies(50)); 		if (kthread_should_stop()) {			jffs2_dbg(1, "%s(): kthread_stop() called\n", __func__);			goto die;		} 		/* Put_super will send a SIGKILL and then wait on the sem.		 */		while (signal_pending(current) || freezing(current)) {			unsigned long signr; 			if (try_to_freeze())				goto again; 			signr = kernel_dequeue_signal(); 			switch(signr) {			case SIGSTOP:				jffs2_dbg(1, "%s(): SIGSTOP received\n",					  __func__);				kernel_signal_stop();				break; 			case SIGKILL:				jffs2_dbg(1, "%s(): SIGKILL received\n",					  __func__);				goto die; 			case SIGHUP:				jffs2_dbg(1, "%s(): SIGHUP received\n",					  __func__);				break;			default:				jffs2_dbg(1, "%s(): signal %ld received\n",					  __func__, signr);			}		}		/* We don't want SIGHUP to interrupt us. STOP and KILL are OK though. */		sigprocmask(SIG_BLOCK, &hupmask, NULL); 		jffs2_dbg(1, "%s(): pass\n", __func__);		if (jffs2_garbage_collect_pass(c) == -ENOSPC) {			pr_notice("No space for garbage collection. Aborting GC thread\n");			goto die;		}	} die:	spin_lock(&c->erase_completion_lock);	c->gc_task = NULL;	spin_unlock(&c->erase_completion_lock);	kthread_complete_and_exit(&c->gc_thread_exit, 0);}