[patch] highmem-2.4.2-A0

[Ingo Molnar]

On Mon, 26 Feb 2001, Andrea Arcangeli wrote:

> The highmem changes in 2.4.2ac3 has a couple of bugs, one relevant
> that can generate deadlocks (re-enable interrupts with io_request_lock
> acquired).

oops, right, the emergency-pool patch was just a quick hack to check
whether this is the final problem affecting RL highmem systems.

the attached highmem-2.4.2-A0 patch does the jist of your fixes, against
-ac4. Differences: no need to complicate highmem.c with pool-fillup on
bootup. It will get refilled after the first disk-accesses anyway.

i'm unsure about the other changes done by your patch, could you explain
them? Notably the pgalloc-3level.h and fault.c changes. Thanks,

        Ingo

--- linux/mm/highmem.c.orig     Mon Feb 26 23:33:17 2001
+++ linux/mm/highmem.c  Mon Feb 26 23:37:02 2001
@@ -217,6 +217,7 @@
 static inline void bounce_end_io (struct buffer_head *bh, int uptodate)
 {
        struct page *page;
+       unsigned long flags;
        struct list_head *tmp;
        struct buffer_head *bh_orig = (struct buffer_head *)(bh->b_private);
 
@@ -231,27 +232,27 @@
                __free_page(page);
        else {
                tmp = &emergency_pages;
-               spin_lock_irq(&emergency_lock);
+               spin_lock_irqsave(&emergency_lock, flags);
                /*
                 * We are abusing page->list to manage
                 * the highmem emergency pool:
                 */
                list_add(&page->list, &emergency_pages);
                nr_emergency_pages++;
-               spin_unlock_irq(&emergency_lock);
+               spin_unlock_irqrestore(&emergency_lock, flags);
        }
        
        if (nr_emergency_pages >= POOL_SIZE)
                kmem_cache_free(bh_cachep, bh);
        else {
                tmp = &emergency_bhs;
-               spin_lock_irq(&emergency_lock);
+               spin_lock_irqsave(&emergency_lock, flags);
                /*
                 * Ditto in the bh case, here we abuse b_inode_buffers:
                 */
                list_add(&bh->b_inode_buffers, &emergency_bhs);
                nr_emergency_bhs++;
-               spin_unlock_irq(&emergency_lock);
+               spin_unlock_irqrestore(&emergency_lock, flags);
        }
 }
 
@@ -297,6 +298,12 @@
        spin_unlock_irq(&emergency_lock);
        if (page)
                return page;
+
+       run_task_queue(&tq_disk);
+
+       current->policy |= SCHED_YIELD;
+       __set_current_state(TASK_RUNNING);
+       schedule();
        goto repeat_alloc;
 }
 
@@ -328,6 +335,12 @@
        spin_unlock_irq(&emergency_lock);
        if (bh)
                return bh;
+
+       run_task_queue(&tq_disk);
+
+       current->policy |= SCHED_YIELD;
+       __set_current_state(TASK_RUNNING);
+       schedule();
        goto repeat_alloc;
 }