1 /* 2 * JFFS2 -- Journalling Flash File System, Version 2. 3 * 4 * Copyright © 2001-2007 Red Hat, Inc. 5 * 6 * Created by David Woodhouse <dwmw2@infradead.org> 7 * 8 * For licensing information, see the file 'LICENCE' in this directory. 9 * 10 */ 11 12 #include <linux/kernel.h> 13 #include <linux/jffs2.h> 14 #include <linux/mtd/mtd.h> 15 #include <linux/completion.h> 16 #include <linux/sched.h> 17 #include <linux/freezer.h> 18 #include <linux/kthread.h> 19 #include "nodelist.h" 20 21 22 static int jffs2_garbage_collect_thread(void *); 23 24 void jffs2_garbage_collect_trigger(struct jffs2_sb_info *c) 25 { 26 assert_spin_locked(&c->erase_completion_lock); 27 if (c->gc_task && jffs2_thread_should_wake(c)) 28 send_sig(SIGHUP, c->gc_task, 1); 29 } 30 31 /* This must only ever be called when no GC thread is currently running */ 32 int jffs2_start_garbage_collect_thread(struct jffs2_sb_info *c) 33 { 34 struct task_struct *tsk; 35 int ret = 0; 36 37 BUG_ON(c->gc_task); 38 39 init_completion(&c->gc_thread_start); 40 init_completion(&c->gc_thread_exit); 41 42 tsk = kthread_run(jffs2_garbage_collect_thread, c, "jffs2_gcd_mtd%d", c->mtd->index); 43 if (IS_ERR(tsk)) { 44 printk(KERN_WARNING "fork failed for JFFS2 garbage collect thread: %ld\n", -PTR_ERR(tsk)); 45 complete(&c->gc_thread_exit); 46 ret = PTR_ERR(tsk); 47 } else { 48 /* Wait for it... */ 49 D1(printk(KERN_DEBUG "JFFS2: Garbage collect thread is pid %d\n", tsk->pid)); 50 wait_for_completion(&c->gc_thread_start); 51 ret = tsk->pid; 52 } 53 54 return ret; 55 } 56 57 void jffs2_stop_garbage_collect_thread(struct jffs2_sb_info *c) 58 { 59 int wait = 0; 60 spin_lock(&c->erase_completion_lock); 61 if (c->gc_task) { 62 D1(printk(KERN_DEBUG "jffs2: Killing GC task %d\n", c->gc_task->pid)); 63 send_sig(SIGKILL, c->gc_task, 1); 64 wait = 1; 65 } 66 spin_unlock(&c->erase_completion_lock); 67 if (wait) 68 wait_for_completion(&c->gc_thread_exit); 69 } 70 71 static int jffs2_garbage_collect_thread(void *_c) 72 { 73 struct jffs2_sb_info *c = _c; 74 75 allow_signal(SIGKILL); 76 allow_signal(SIGSTOP); 77 allow_signal(SIGCONT); 78 79 c->gc_task = current; 80 complete(&c->gc_thread_start); 81 82 set_user_nice(current, 10); 83 84 set_freezable(); 85 for (;;) { 86 allow_signal(SIGHUP); 87 again: 88 spin_lock(&c->erase_completion_lock); 89 if (!jffs2_thread_should_wake(c)) { 90 set_current_state (TASK_INTERRUPTIBLE); 91 spin_unlock(&c->erase_completion_lock); 92 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread sleeping...\n")); 93 schedule(); 94 } else 95 spin_unlock(&c->erase_completion_lock); 96 97 98 /* Problem - immediately after bootup, the GCD spends a lot 99 * of time in places like jffs2_kill_fragtree(); so much so 100 * that userspace processes (like gdm and X) are starved 101 * despite plenty of cond_resched()s and renicing. Yield() 102 * doesn't help, either (presumably because userspace and GCD 103 * are generally competing for a higher latency resource - 104 * disk). 105 * This forces the GCD to slow the hell down. Pulling an 106 * inode in with read_inode() is much preferable to having 107 * the GC thread get there first. */ 108 schedule_timeout_interruptible(msecs_to_jiffies(50)); 109 110 if (kthread_should_stop()) { 111 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): kthread_stop() called.\n")); 112 goto die; 113 } 114 115 /* Put_super will send a SIGKILL and then wait on the sem. 116 */ 117 while (signal_pending(current) || freezing(current)) { 118 siginfo_t info; 119 unsigned long signr; 120 121 if (try_to_freeze()) 122 goto again; 123 124 signr = dequeue_signal_lock(current, ¤t->blocked, &info); 125 126 switch(signr) { 127 case SIGSTOP: 128 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): SIGSTOP received.\n")); 129 set_current_state(TASK_STOPPED); 130 schedule(); 131 break; 132 133 case SIGKILL: 134 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): SIGKILL received.\n")); 135 goto die; 136 137 case SIGHUP: 138 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): SIGHUP received.\n")); 139 break; 140 default: 141 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): signal %ld received\n", signr)); 142 } 143 } 144 /* We don't want SIGHUP to interrupt us. STOP and KILL are OK though. */ 145 disallow_signal(SIGHUP); 146 147 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): pass\n")); 148 if (jffs2_garbage_collect_pass(c) == -ENOSPC) { 149 printk(KERN_NOTICE "No space for garbage collection. Aborting GC thread\n"); 150 goto die; 151 } 152 } 153 die: 154 spin_lock(&c->erase_completion_lock); 155 c->gc_task = NULL; 156 spin_unlock(&c->erase_completion_lock); 157 complete_and_exit(&c->gc_thread_exit, 0); 158 } 159