Messages in this thread Patch in this message | | | Subject | [PATCH] mm, memory-failure: Fix spinlock vs mutex order | From | Peter Zijlstra <> | Date | Fri, 17 Jun 2011 21:53:05 +0200 |
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On Fri, 2011-06-17 at 20:32 +0200, Peter Zijlstra wrote: > Aside from the THP thing there's a user in memory-failure.c, which looks > to be broken as it is because its calling things under tasklist_lock > which isn't preemptible, but it looks like we can simply swap the > tasklist_lock vs page_lock_anon_vma. >
I thought about maybe using rcu, but then thought the thing is probably wanting to exclude new tasks as it wants to kill all mm users.
--- Subject: mm, memory-failure: Fix spinlock vs mutex order
We cannot take a mutex while holding a spinlock, so flip the order as its documented to be random.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> --- mm/memory-failure.c | 21 ++++++--------------- mm/rmap.c | 5 ++--- 2 files changed, 8 insertions(+), 18 deletions(-)
diff --git a/mm/memory-failure.c b/mm/memory-failure.c index eac0ba5..740c4f5 100644 --- a/mm/memory-failure.c +++ b/mm/memory-failure.c @@ -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); } /* diff --git a/mm/rmap.c b/mm/rmap.c index 0eb463e..5e51855 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -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) - * ->tasklist_lock - * anon_vma->mutex (memory_failure, collect_procs_anon) + * anon_vma->mutex,mapping->i_mutex (memory_failure, collect_procs_anon) + * ->tasklist_lock * pte map lock */
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