On Sat, 15 Sep 2012 15:50:07 +0200
Sasha Levin <levinsasha928@xxxxxxxxx> wrote:
> Hi all,
>
> While fuzzing with trinity within a KVM tools guest on a linux-next kernel, I
> got the lockdep warning at the bottom of this mail.
>
> I've tried figuring out where it was introduced, but haven't found any sign that
> any of the code in that area changed recently, so I'm probably missing something...
>
>
> [ 157.966399] =========================================================
> [ 157.968523] [ INFO: possible irq lock inversion dependency detected ]
> [ 157.970029] 3.6.0-rc5-next-20120914-sasha-00001-g802bf6c-dirty #340 Tainted: G W
> [ 157.970029] ---------------------------------------------------------
> [ 157.970029] trinity-child38/6642 just changed the state of lock:
> [ 157.970029] (&(&mapping->tree_lock)->rlock){+.+...}, at: [<ffffffff8120cafc>]
> invalidate_inode_pages2_range+0x20c/0x3c0
> [ 157.970029] but this lock was taken by another, SOFTIRQ-safe lock in the past:
> [ 157.970029] (&(&new->queue_lock)->rlock){..-...}
>
> [snippage]
gack, what a mess. Thanks for the report. AFAICT, what has happened is:
invalidate_complete_page2()
->spin_lock_irq(&mapping->tree_lock)
->clear_page_mlock()
__clear_page_mlock()
->isolate_lru_page()
->spin_lock_irq(&zone->lru_lock)
->spin_unlock_irq(&zone->lru_lock)
whoops. isolate_lru_page() just enabled local interrupts while we're
holding ->tree_lock, which is supposed to be an irq-save lock. And in
a rather obscure way, lockdep caught it.
Problem is, I cannot find any recent change which might have triggered
this.
I don't know how repeatable this is for you (not very at all, I
suspect). This?
From: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Subject: mm: isolate_lru_page(): don't enable local interrupts
isolate_lru_page() is called with local interrupts disabled, via
invalidate_complete_page2()
->spin_lock_irq(&mapping->tree_lock)
->clear_page_mlock()
__clear_page_mlock()
->isolate_lru_page()
so it should not unconditionally enable local interrupts.
Sasha hit a lockdep warning when running Trinity as a result of this.
Reported-by: Sasha Levin <levinsasha928@xxxxxxxxx>
Cc: Mel Gorman <mel@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/vmscan.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff -puN mm/vmscan.c~mm-isolate_lru_page-dont-enable-local-interrupts mm/vmscan.c
--- a/mm/vmscan.c~mm-isolate_lru_page-dont-enable-local-interrupts
+++ a/mm/vmscan.c
@@ -1161,8 +1161,9 @@ int isolate_lru_page(struct page *page)
if (PageLRU(page)) {
struct zone *zone = page_zone(page);
struct lruvec *lruvec;
+ unsigned long flags;
- spin_lock_irq(&zone->lru_lock);
+ spin_lock_irqsave(&zone->lru_lock, flags);
lruvec = mem_cgroup_page_lruvec(page, zone);
if (PageLRU(page)) {
int lru = page_lru(page);
@@ -1171,7 +1172,7 @@ int isolate_lru_page(struct page *page)
del_page_from_lru_list(page, lruvec, lru);
ret = 0;
}
- spin_unlock_irq(&zone->lru_lock);
+ spin_unlock_irqrestore(&zone->lru_lock, flags);
}
return ret;
}
_
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