Messages in this thread Patch in this message | | | Date | Tue, 12 May 2009 17:13:56 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | [PATCH][BUGFIX] memcg: fix for deadlock between lock_page_cgroup and mapping tree_lock |
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On Tue, 12 May 2009 17:00:07 +0900 Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote: > hmm, I see. > cache_charge is outside of tree_lock, so moving uncharge would make sense. > IMHO, we should make the period of spinlock as small as possible, > and charge/uncharge of pagecache/swapcache is protected by page lock, not tree_lock. > How about this ? == From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
As Nishimura pointed out, mapping->tree_lock can be aquired from interrupt context. Then, following dead lock can occur. Assume "A" as a page.
CPU0: lock_page_cgroup(A) interrupted -> take mapping->tree_lock. CPU1: take mapping->tree_lock -> lock_page_cgroup(A)
This patch tries to fix above deadlock by moving memcg's hook to out of mapping->tree_lock.
After this patch, lock_page_cgroup() is not called under mapping->tree_lock.
Making Nishimura's first fix more fundamanetal for avoiding to add special case.
Reported-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
--- mm/filemap.c | 6 +++--- mm/swap_state.c | 2 +- mm/truncate.c | 1 + mm/vmscan.c | 2 ++ 4 files changed, 7 insertions(+), 4 deletions(-)
Index: mmotm-2.6.30-May07/mm/filemap.c =================================================================== --- mmotm-2.6.30-May07.orig/mm/filemap.c +++ mmotm-2.6.30-May07/mm/filemap.c @@ -121,7 +121,6 @@ void __remove_from_page_cache(struct pag mapping->nrpages--; __dec_zone_page_state(page, NR_FILE_PAGES); BUG_ON(page_mapped(page)); - mem_cgroup_uncharge_cache_page(page); /* * Some filesystems seem to re-dirty the page even after @@ -145,6 +144,7 @@ void remove_from_page_cache(struct page spin_lock_irq(&mapping->tree_lock); __remove_from_page_cache(page); spin_unlock_irq(&mapping->tree_lock); + mem_cgroup_uncharge_cache_page(page); } static int sync_page(void *word) @@ -476,13 +476,13 @@ int add_to_page_cache_locked(struct page if (likely(!error)) { mapping->nrpages++; __inc_zone_page_state(page, NR_FILE_PAGES); + spin_unlock_irq(&mapping->tree_lock); } else { page->mapping = NULL; + spin_unlock_irq(&mapping->tree_lock); mem_cgroup_uncharge_cache_page(page); page_cache_release(page); } - - spin_unlock_irq(&mapping->tree_lock); radix_tree_preload_end(); } else mem_cgroup_uncharge_cache_page(page); Index: mmotm-2.6.30-May07/mm/swap_state.c =================================================================== --- mmotm-2.6.30-May07.orig/mm/swap_state.c +++ mmotm-2.6.30-May07/mm/swap_state.c @@ -121,7 +121,6 @@ void __delete_from_swap_cache(struct pag total_swapcache_pages--; __dec_zone_page_state(page, NR_FILE_PAGES); INC_CACHE_INFO(del_total); - mem_cgroup_uncharge_swapcache(page, ent); } /** @@ -191,6 +190,7 @@ void delete_from_swap_cache(struct page __delete_from_swap_cache(page); spin_unlock_irq(&swapper_space.tree_lock); + mem_cgroup_uncharge_swapcache(page, ent); swap_free(entry); page_cache_release(page); } Index: mmotm-2.6.30-May07/mm/truncate.c =================================================================== --- mmotm-2.6.30-May07.orig/mm/truncate.c +++ mmotm-2.6.30-May07/mm/truncate.c @@ -359,6 +359,7 @@ invalidate_complete_page2(struct address BUG_ON(page_has_private(page)); __remove_from_page_cache(page); spin_unlock_irq(&mapping->tree_lock); + mem_cgroup_uncharge_cache_page(page); page_cache_release(page); /* pagecache ref */ return 1; failed: Index: mmotm-2.6.30-May07/mm/vmscan.c =================================================================== --- mmotm-2.6.30-May07.orig/mm/vmscan.c +++ mmotm-2.6.30-May07/mm/vmscan.c @@ -477,10 +477,12 @@ static int __remove_mapping(struct addre swp_entry_t swap = { .val = page_private(page) }; __delete_from_swap_cache(page); spin_unlock_irq(&mapping->tree_lock); + mem_cgroup_uncharge_swapcache(page); swap_free(swap); } else { __remove_from_page_cache(page); spin_unlock_irq(&mapping->tree_lock); + mem_cgroup_uncharge_cache_page(page); } return 1;
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