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   1 /*
   2  * JFFS2 -- Journalling Flash File System, Version 2.
   3  *
   4  * Copyright (C) 2001-2003 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  * $Id: background.c,v 1.54 2005/05/20 21:37:12 gleixner Exp $
  11  *
  12  */
  13
  14 #include <linux/kernel.h>
  15 #include <linux/jffs2.h>
  16 #include <linux/mtd/mtd.h>
  17 #include <linux/completion.h>
  18 #include <linux/sched.h>
  19 #include <linux/freezer.h>
  20 #include "nodelist.h"
  21
  22
  23 static int jffs2_garbage_collect_thread(void *);
  24
  25 void jffs2_garbage_collect_trigger(struct jffs2_sb_info *c)
  26 {
  27         spin_lock(&c->erase_completion_lock);
  28         if (c->gc_task && jffs2_thread_should_wake(c))
  29                 send_sig(SIGHUP, c->gc_task, 1);
  30         spin_unlock(&c->erase_completion_lock);
  31 }
  32
  33 /* This must only ever be called when no GC thread is currently running */
  34 int jffs2_start_garbage_collect_thread(struct jffs2_sb_info *c)
  35 {
  36         pid_t pid;
  37         int ret = 0;
  38
  39         BUG_ON(c->gc_task);
  40
  41         init_completion(&c->gc_thread_start);
  42         init_completion(&c->gc_thread_exit);
  43
  44         pid = kernel_thread(jffs2_garbage_collect_thread, c, CLONE_FS|CLONE_FILES);
  45         if (pid < 0) {
  46                 printk(KERN_WARNING "fork failed for JFFS2 garbage collect thread: %d\n", -pid);
  47                 complete(&c->gc_thread_exit);
  48                 ret = pid;
  49         } else {
  50                 /* Wait for it... */
  51                 D1(printk(KERN_DEBUG "JFFS2: Garbage collect thread is pid %d\n", pid));
  52                 wait_for_completion(&c->gc_thread_start);
  53         }
  54
  55         return ret;
  56 }
  57
  58 void jffs2_stop_garbage_collect_thread(struct jffs2_sb_info *c)
  59 {
  60         int wait = 0;
  61         spin_lock(&c->erase_completion_lock);
  62         if (c->gc_task) {
  63                 D1(printk(KERN_DEBUG "jffs2: Killing GC task %d\n", c->gc_task->pid));
  64                 send_sig(SIGKILL, c->gc_task, 1);
  65                 wait = 1;
  66         }
  67         spin_unlock(&c->erase_completion_lock);
  68         if (wait)
  69                 wait_for_completion(&c->gc_thread_exit);
  70 }
  71
  72 static int jffs2_garbage_collect_thread(void *_c)
  73 {
  74         struct jffs2_sb_info *c = _c;
  75
  76         daemonize("jffs2_gcd_mtd%d", c->mtd->index);
  77         allow_signal(SIGKILL);
  78         allow_signal(SIGSTOP);
  79         allow_signal(SIGCONT);
  80
  81         c->gc_task = current;
  82         complete(&c->gc_thread_start);
  83
  84         set_user_nice(current, 10);
  85
  86         for (;;) {
  87                 allow_signal(SIGHUP);
  88
  89                 if (!jffs2_thread_should_wake(c)) {
  90                         set_current_state (TASK_INTERRUPTIBLE);
  91                         D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread sleeping...\n"));
  92                         /* Yes, there's a race here; we checked jffs2_thread_should_wake()
  93                            before setting current->state to TASK_INTERRUPTIBLE. But it doesn't
  94                            matter - We don't care if we miss a wakeup, because the GC thread
  95                            is only an optimisation anyway. */
  96                         schedule();
  97                 }
  98
  99                 if (try_to_freeze())
 100                         continue;
 101
 102                 /* This thread is purely an optimisation. But if it runs when
 103                    other things could be running, it actually makes things a
 104                    lot worse. Use yield() and put it at the back of the runqueue
 105                    every time. Especially during boot, pulling an inode in
 106                    with read_inode() is much preferable to having the GC thread
 107                    get there first. */
 108                 yield();
 109
 110                 /* Put_super will send a SIGKILL and then wait on the sem.
 111                  */
 112                 while (signal_pending(current)) {
 113                         siginfo_t info;
 114                         unsigned long signr;
 115
 116                         signr = dequeue_signal_lock(current, &current->blocked, &info);
 117
 118                         switch(signr) {
 119                         case SIGSTOP:
 120                                 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): SIGSTOP received.\n"));
 121                                 set_current_state(TASK_STOPPED);
 122                                 schedule();
 123                                 break;
 124
 125                         case SIGKILL:
 126                                 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): SIGKILL received.\n"));
 127                                 goto die;
 128
 129                         case SIGHUP:
 130                                 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): SIGHUP received.\n"));
 131                                 break;
 132                         default:
 133                                 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): signal %ld received\n", signr));
 134                         }
 135                 }
 136                 /* We don't want SIGHUP to interrupt us. STOP and KILL are OK though. */
 137                 disallow_signal(SIGHUP);
 138
 139                 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): pass\n"));
 140                 if (jffs2_garbage_collect_pass(c) == -ENOSPC) {
 141                         printk(KERN_NOTICE "No space for garbage collection. Aborting GC thread\n");
 142                         goto die;
 143                 }
 144         }
 145  die:
 146         spin_lock(&c->erase_completion_lock);
 147         c->gc_task = NULL;
 148         spin_unlock(&c->erase_completion_lock);
 149         complete_and_exit(&c->gc_thread_exit, 0);
 150 }