Commit 4ab1a3e6 authored by Andrew Morton's avatar Andrew Morton Committed by Linus Torvalds

[PATCH] tighter locking in pdflush

Had a weird oops from Bill Irwin - the pdflush_list was corrupt.

The only thing I can think of is that something sprayed out a wakeup
when it shouldn't.  So tighten things up against that, and add some
printks to catch it if it happens again.
parent 57eb0613
......@@ -79,9 +79,9 @@ static unsigned long last_empty_jifs;
*/
struct pdflush_work {
struct task_struct *who; /* The thread */
void (*fn)(unsigned long); /* A callback function for pdflush to work on */
unsigned long arg0; /* An argument to the callback function */
struct list_head list; /* On pdflush_list, when the thread is idle */
void (*fn)(unsigned long); /* A callback function */
unsigned long arg0; /* An argument to the callback */
struct list_head list; /* On pdflush_list, when idle */
unsigned long when_i_went_to_sleep;
};
......@@ -99,23 +99,34 @@ static int __pdflush(struct pdflush_work *my_work)
current->flags |= PF_FLUSHER;
my_work->fn = NULL;
my_work->who = current;
INIT_LIST_HEAD(&my_work->list);
spin_lock_irq(&pdflush_lock);
nr_pdflush_threads++;
// printk("pdflush %d [%d] starts\n", nr_pdflush_threads, current->pid);
for ( ; ; ) {
struct pdflush_work *pdf;
list_add(&my_work->list, &pdflush_list);
my_work->when_i_went_to_sleep = jiffies;
set_current_state(TASK_INTERRUPTIBLE);
list_move(&my_work->list, &pdflush_list);
my_work->when_i_went_to_sleep = jiffies;
spin_unlock_irq(&pdflush_lock);
if (current->flags & PF_FREEZE)
refrigerator(PF_IOTHREAD);
schedule();
if (my_work->fn)
spin_lock_irq(&pdflush_lock);
if (!list_empty(&my_work->list)) {
printk("pdflush: bogus wakeup!\n");
my_work->fn = NULL;
continue;
}
if (my_work->fn == NULL) {
printk("pdflush: NULL work function\n");
continue;
}
spin_unlock_irq(&pdflush_lock);
(*my_work->fn)(my_work->arg0);
/*
......@@ -132,6 +143,7 @@ static int __pdflush(struct pdflush_work *my_work)
}
spin_lock_irq(&pdflush_lock);
my_work->fn = NULL;
/*
* Thread destruction: For how long has the sleepiest
......@@ -143,13 +155,12 @@ static int __pdflush(struct pdflush_work *my_work)
continue;
pdf = list_entry(pdflush_list.prev, struct pdflush_work, list);
if (jiffies - pdf->when_i_went_to_sleep > 1 * HZ) {
pdf->when_i_went_to_sleep = jiffies; /* Limit exit rate */
/* Limit exit rate */
pdf->when_i_went_to_sleep = jiffies;
break; /* exeunt */
}
my_work->fn = NULL;
}
nr_pdflush_threads--;
// printk("pdflush %d [%d] ends\n", nr_pdflush_threads, current->pid);
spin_unlock_irq(&pdflush_lock);
return 0;
}
......@@ -191,11 +202,10 @@ int pdflush_operation(void (*fn)(unsigned long), unsigned long arg0)
list_del_init(&pdf->list);
if (list_empty(&pdflush_list))
last_empty_jifs = jiffies;
spin_unlock_irqrestore(&pdflush_lock, flags);
pdf->fn = fn;
pdf->arg0 = arg0;
wmb(); /* ? */
wake_up_process(pdf->who);
spin_unlock_irqrestore(&pdflush_lock, flags);
}
return ret;
}
......
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