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Date: Mon, 17 Sep 2012 16:22:48 -0700 From: Andrew Morton <akpm@...ux-foundation.org> To: Sasha Levin <levinsasha928@...il.com> Cc: axboe@...nel.dk, Tejun Heo <tj@...nel.org>, linux-mm <linux-mm@...ck.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Dave Jones <davej@...hat.com> Subject: Re: blk, mm: lockdep irq lock inversion in linux-next On Sat, 15 Sep 2012 15:50:07 +0200 Sasha Levin <levinsasha928@...il.com> 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@...ux-foundation.org> 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@...il.com> Cc: Mel Gorman <mel@....ul.ie> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org> --- 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; } _ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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