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Commit 9b679320 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Linus Torvalds
Browse files

mm/memory-failure.c: fix spinlock vs mutex order 



We cannot take a mutex while holding a spinlock, so flip the order and
fix the locking documentation.

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: default avatarAndi Kleen <ak@linux.intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent aa2c96d6

mm/memory-failure.c

+6 −15
Original line number Diff line number Diff line
@@ -391,10 +391,11 @@ static void collect_procs_anon(struct page *page, struct list_head *to_kill, 
	struct task_struct *tsk;

	struct anon_vma *av;



	read_lock(&tasklist_lock);

	av = page_lock_anon_vma(page);

	if (av == NULL)	/* Not actually mapped anymore */

		goto out;

		return;



	read_lock(&tasklist_lock);

	for_each_process (tsk) {

		struct anon_vma_chain *vmac;
@@ -408,9 +409,8 @@ static void collect_procs_anon(struct page *page, struct list_head *to_kill, 
				add_to_kill(tsk, page, vma, to_kill, tkc);

		}

	}

	page_unlock_anon_vma(av);

out:

	read_unlock(&tasklist_lock);

	page_unlock_anon_vma(av);

}



/*
@@ -424,17 +424,8 @@ static void collect_procs_file(struct page *page, struct list_head *to_kill, 
	struct prio_tree_iter iter;

	struct address_space *mapping = page->mapping;



	/*

	 * A note on the locking order between the two locks.

	 * We don't rely on this particular order.

	 * If you have some other code that needs a different order

	 * feel free to switch them around. Or add a reverse link

	 * from mm_struct to task_struct, then this could be all

	 * done without taking tasklist_lock and looping over all tasks.

	 */



	read_lock(&tasklist_lock);

	mutex_lock(&mapping->i_mmap_mutex);

	read_lock(&tasklist_lock);

	for_each_process(tsk) {

		pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
@@ -454,8 +445,8 @@ static void collect_procs_file(struct page *page, struct list_head *to_kill, 
				add_to_kill(tsk, page, vma, to_kill, tkc);

		}

	}

	mutex_unlock(&mapping->i_mmap_mutex);

	read_unlock(&tasklist_lock);

	mutex_unlock(&mapping->i_mmap_mutex);

}



/*

mm/rmap.c

+2 −3
Original line number Diff line number Diff line
@@ -38,9 +38,8 @@ 
 *                           in arch-dependent flush_dcache_mmap_lock,

 *                           within inode_wb_list_lock in __sync_single_inode)

 *

 * (code doesn't rely on that order so it could be switched around)

 * anon_vma->mutex,mapping->i_mutex      (memory_failure, collect_procs_anon)

 *   ->tasklist_lock

 *   anon_vma->mutex      (memory_failure, collect_procs_anon)

 *     pte map lock

 */