Messages in this thread Patch in this message | | | Date | Tue, 2 May 2006 15:59:20 +0200 | From | Ingo Molnar <> | Subject | [patch, 2.6.17-rc3-mm1] swap-prefetch-fix.patch |
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From: Ingo Molnar <mingo@elte.hu>
fix potential swap-prefetch deadlock: swapped.lock must be taken in an irq-safe manner, because it can be taken while holding an irq-safe lock in the following code sequence:
[<c014646e>] lockdep_acquire+0x69/0x82 [<c10c4fc1>] _spin_lock+0x21/0x2f [<c0175e7d>] add_to_swapped_list+0x1f/0x13b [<c016780d>] remove_mapping+0x84/0xc3 [<c0167c47>] shrink_inactive_list+0x3fb/0x705 [<c016800a>] shrink_zone+0xb9/0xd8 [<c01682bc>] kswapd+0x293/0x38a [<c013f271>] kthread+0xa6/0xd3
found by the locking correctness validator. The full validator output is:
====================================================== [ BUG: hard-safe -> hard-unsafe lock order detected! ] ------------------------------------------------------ kswapd0/1173 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire: (swapped.lock){--..}, at: [<c0175e7d>] add_to_swapped_list+0x1f/0x13b
and this task is already holding: (swapper_space.tree_lock){+...}, at: [<c01677a5>] remove_mapping+0x1c/0xc3 which would create a new lock dependency: (swapper_space.tree_lock){+...} -> (swapped.lock){--..}
but this new dependency connects a hard-irq-safe lock: (swapper_space.tree_lock){+...} ... which became hard-irq-safe at: [<c014646e>] lockdep_acquire+0x69/0x82 [<c10c52a2>] _write_lock_irqsave+0x2a/0x3a [<c0164c6f>] test_clear_page_writeback+0x48/0xbc [<c0165a57>] rotate_reclaimable_page+0x8b/0xb4 [<c015e2c3>] end_page_writeback+0x18/0x45 [<c0173153>] end_swap_bio_write+0x28/0x36 [<c018549a>] bio_endio+0x66/0x6e [<c0532613>] __end_that_request_first+0x23c/0x559 [<c0532945>] end_that_request_first+0xb/0xd [<c09cae20>] ide_end_request+0xa8/0xf1 [<c09d1c44>] ide_dma_intr+0x54/0x8f [<c09cc011>] ide_intr+0x147/0x1a7 [<c015adc7>] handle_IRQ_event+0x1f/0x4f [<c015ae9d>] __do_IRQ+0xa6/0x111 [<c0106287>] do_IRQ+0x8c/0xad
to a hard-irq-unsafe lock: (swapped.lock){--..} ... which became hard-irq-unsafe at: ... [<c014646e>] lockdep_acquire+0x69/0x82 [<c10c4fc1>] _spin_lock+0x21/0x2f [<c01763fc>] kprefetchd+0x3eb/0x40b [<c013f271>] kthread+0xa6/0xd3 [<c0102005>] kernel_thread_helper+0x5/0xb
which could potentially lead to deadlocks!
other info that might help us debug this:
1 locks held by kswapd0/1173: #0: (swapper_space.tree_lock){+...}, at: [<c01677a5>] remove_mapping+0x1c/0xc3
the hard-irq-safe lock's dependencies: -> (swapper_space.tree_lock){+...} ops: 121 { initial-use at: [<c014646e>] lockdep_acquire+0x69/0x82 [<c10c505e>] _write_lock_irq+0x27/0x35 [<c017341a>] __add_to_swap_cache+0x65/0x149 [<c0173512>] move_to_swap_cache+0x14/0x62 [<c0178af8>] shmem_writepage+0x10c/0x1b5 [<c01672e9>] pageout+0x119/0x1cc [<c0167b73>] shrink_inactive_list+0x327/0x705 [<c016800a>] shrink_zone+0xb9/0xd8 [<c01684f5>] try_to_free_pages+0x142/0x221 [<c0163e36>] __alloc_pages+0x1d9/0x325 [<c015f919>] generic_file_buffered_write+0x189/0x5cd [<c0160f8d>] __generic_file_aio_write_nolock+0x450/0x48d [<c01611fa>] generic_file_aio_write+0x6e/0xc1 [<c02ab0c2>] ext3_file_write+0x1a/0x8b [<c017fe22>] do_sync_write+0xb1/0xe6 [<c01807da>] vfs_write+0xcd/0x176 [<c0180e7d>] sys_write+0x3b/0x71 [<c10c5abb>] syscall_call+0x7/0xb in-hardirq-W at: [<c014646e>] lockdep_acquire+0x69/0x82 [<c10c52a2>] _write_lock_irqsave+0x2a/0x3a [<c0164c6f>] test_clear_page_writeback+0x48/0xbc [<c0165a57>] rotate_reclaimable_page+0x8b/0xb4 [<c015e2c3>] end_page_writeback+0x18/0x45 [<c0173153>] end_swap_bio_write+0x28/0x36 [<c018549a>] bio_endio+0x66/0x6e [<c0532613>] __end_that_request_first+0x23c/0x559 [<c0532945>] end_that_request_first+0xb/0xd [<c09cae20>] ide_end_request+0xa8/0xf1 [<c09d1c44>] ide_dma_intr+0x54/0x8f [<c09cc011>] ide_intr+0x147/0x1a7 [<c015adc7>] handle_IRQ_event+0x1f/0x4f [<c015ae9d>] __do_IRQ+0xa6/0x111 [<c0106287>] do_IRQ+0x8c/0xad } ... key at: [<c14d4e64>] swapper_space+0x24/0xfc
the hard-irq-unsafe lock's dependencies: -> (swapped.lock){--..} ops: 2 { initial-use at: [<c014646e>] lockdep_acquire+0x69/0x82 [<c10c4fc1>] _spin_lock+0x21/0x2f [<c01763fc>] kprefetchd+0x3eb/0x40b [<c013f271>] kthread+0xa6/0xd3 [<c0102005>] kernel_thread_helper+0x5/0xb softirq-on-W at: [<c014646e>] lockdep_acquire+0x69/0x82 [<c10c4fc1>] _spin_lock+0x21/0x2f [<c01763fc>] kprefetchd+0x3eb/0x40b [<c013f271>] kthread+0xa6/0xd3 [<c0102005>] kernel_thread_helper+0x5/0xb hardirq-on-W at: [<c014646e>] lockdep_acquire+0x69/0x82 [<c10c4fc1>] _spin_lock+0x21/0x2f [<c01763fc>] kprefetchd+0x3eb/0x40b [<c013f271>] kthread+0xa6/0xd3 [<c0102005>] kernel_thread_helper+0x5/0xb } ... key at: [<c14d5658>] swapped+0x18/0x60
stack backtrace: [<c0104e7f>] show_trace+0xd/0xf [<c0104e96>] dump_stack+0x15/0x17 [<c0144cd3>] check_usage+0x1f4/0x201 [<c0146238>] __lockdep_acquire+0x873/0xa40 [<c014646e>] lockdep_acquire+0x69/0x82 [<c10c4fc1>] _spin_lock+0x21/0x2f [<c0175e7d>] add_to_swapped_list+0x1f/0x13b [<c016780d>] remove_mapping+0x84/0xc3 [<c0167c47>] shrink_inactive_list+0x3fb/0x705 [<c016800a>] shrink_zone+0xb9/0xd8 [<c01682bc>] kswapd+0x293/0x38a [<c013f271>] kthread+0xa6/0xd3 [<c0102005>] kernel_thread_helper+0x5/0xb
Signed-off-by: Ingo Molnar <mingo@elte.hu>
----
--- mm/swap_prefetch.c | 17 +++++++++-------- 1 files changed, 9 insertions(+), 8 deletions(-)
Index: linux/mm/swap_prefetch.c =================================================================== --- linux.orig/mm/swap_prefetch.c +++ linux/mm/swap_prefetch.c @@ -65,7 +65,7 @@ inline void delay_swap_prefetch(void) void add_to_swapped_list(struct page *page) { struct swapped_entry *entry; - unsigned long index; + unsigned long index, flags; int wakeup; if (!swap_prefetch) @@ -73,7 +73,7 @@ void add_to_swapped_list(struct page *pa wakeup = 0; - spin_lock(&swapped.lock); + spin_lock_irqsave(&swapped.lock, flags); if (swapped.count >= swapped.maxcount) { /* * We limit the number of entries to 2/3 of physical ram. @@ -112,7 +112,7 @@ void add_to_swapped_list(struct page *pa } out_locked: - spin_unlock(&swapped.lock); + spin_unlock_irqrestore(&swapped.lock, flags); /* Do the wakeup outside the lock to shorten lock hold time. */ if (wakeup) @@ -433,6 +433,7 @@ static enum trickle_return trickle_swap( { enum trickle_return ret = TRICKLE_DELAY; struct swapped_entry *entry; + unsigned long flags; /* * If laptop_mode is enabled don't prefetch to avoid hard drives @@ -451,10 +452,10 @@ static enum trickle_return trickle_swap( if (!prefetch_suitable()) break; - spin_lock(&swapped.lock); + spin_lock_irqsave(&swapped.lock, flags); if (list_empty(&swapped.list)) { ret = TRICKLE_FAILED; - spin_unlock(&swapped.lock); + spin_unlock_irqrestore(&swapped.lock, flags); break; } @@ -473,7 +474,7 @@ static enum trickle_return trickle_swap( * be a reason we could not swap them back in so * delay attempting further prefetching. */ - spin_unlock(&swapped.lock); + spin_unlock_irqrestore(&swapped.lock, flags); break; } @@ -484,12 +485,12 @@ static enum trickle_return trickle_swap( * not suitable for prefetching so skip it. */ entry = prev_swapped_entry(entry); - spin_unlock(&swapped.lock); + spin_unlock_irqrestore(&swapped.lock, flags); continue; } swp_entry = entry->swp_entry; entry = prev_swapped_entry(entry); - spin_unlock(&swapped.lock); + spin_unlock_irqrestore(&swapped.lock, flags); if (trickle_swap_cache_async(swp_entry, node) == TRICKLE_DELAY) break; - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.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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