zram: lockdep spew for zram->init_lock

From: Sasha Levin
Date: Thu Feb 27 2014 - 09:48:57 EST

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Hi all,

I've stumbled on the following spew while fuzzing with trinity inside a KVM tools guest running latest -next. It looks like a false positive (we only set size for uninitialized devices, so we can't deadlock on them being in-use) but I'd really like someone to confirm it before I write it down as such.

[ 2655.365684] =================================
[ 2655.368278] [ INFO: inconsistent lock state ]
[ 2655.370163] 3.14.0-rc4-next-20140226-sasha-00013-g082bdac-dirty #4 Tainted: G W
[ 2655.371972] ---------------------------------
[ 2655.371972] inconsistent {RECLAIM_FS-ON-W} -> {IN-RECLAIM_FS-R} usage.
[ 2655.371972] kswapd30/5352 [HC0[0]:SC0[0]:HE1:SE1] takes:
[ 2655.371972] (&zram->init_lock){+++++-}, at: [<drivers/block/zram/zram_drv.c:663>] zram_make_request+0x2a/0xc0
[ 2655.371972] {RECLAIM_FS-ON-W} state was registered at:
[ 2655.371972] [<kernel/locking/lockdep.c:2523>] mark_held_locks+0x6c/0x90
[ 2655.371972] [<kernel/locking/lockdep.c:2745 kernel/locking/lockdep.c:2760>] lockdep_trace_alloc+0xfd/0x140
[ 2655.371972] [<mm/slub.c:965 mm/slub.c:2402 mm/slub.c:2475 mm/slub.c:2492>] kmem_cache_alloc_trace+0x32/0x2e0
[ 2655.371972] [<include/linux/slab.h:453 drivers/block/zram/zram_drv.c:172>] zram_meta_alloc+0x20/0x150
[ 2655.371972] [<drivers/block/zram/zram_drv.c:554>] disksize_store+0x8e/0xf0
[ 2655.371972] [<drivers/base/core.c:139>] dev_attr_store+0x1b/0x20
[ 2655.371972] [<fs/sysfs/file.c:114>] sysfs_kf_write+0x4a/0x60
[ 2655.371972] [<fs/kernfs/file.c:299>] kernfs_fop_write+0x110/0x190
[ 2655.371972] [<fs/read_write.c:473>] vfs_write+0xe3/0x1d0
[ 2655.371972] [<fs/read_write.c:523 fs/read_write.c:515>] SyS_write+0x5d/0xa0
[ 2655.371972] [<arch/x86/kernel/entry_64.S:749>] tracesys+0xdd/0xe2
[ 2655.371972] irq event stamp: 10207
[ 2655.371972] hardirqs last enabled at (10207): [<arch/x86/include/asm/paravirt.h:809 block/blk-throttle.c:982>] throtl_update_dispatch_stats+0x15d/0x1a0
[ 2655.371972] hardirqs last disabled at (10206): [<block/blk-throttle.c:977>] throtl_update_dispatch_stats+0xa4/0x1a0
[ 2655.371972] softirqs last enabled at (10172): [<arch/x86/include/asm/preempt.h:22 kernel/softirq.c:297>] __do_softirq+0x447/0x4f0
[ 2655.371972] softirqs last disabled at (10165): [<kernel/softirq.c:347 kernel/softirq.c:388>] irq_exit+0x83/0x160
[ 2655.371972]
[ 2655.371972] other info that might help us debug this:
[ 2655.371972] Possible unsafe locking scenario:
[ 2655.371972]
[ 2655.371972] CPU0
[ 2655.371972] ----
[ 2655.371972] lock(&zram->init_lock);
[ 2655.371972] <Interrupt>
[ 2655.371972] lock(&zram->init_lock);
[ 2655.371972]
[ 2655.371972] *** DEADLOCK ***
[ 2655.371972]
[ 2655.371972] no locks held by kswapd30/5352.
[ 2655.371972]
[ 2655.371972] stack backtrace:
[ 2655.371972] CPU: 78 PID: 5352 Comm: kswapd30 Tainted: G W 3.14.0-rc4-next-20140226-sasha-00013-g082bdac-dirty #4
[ 2655.371972] ffff880636f98cc0 ffff880636f8d3f8 ffffffff843882e5 0000000000000000
[ 2655.371972] ffff880636f98000 ffff880636f8d458 ffffffff811a09f7 0000000000000000
[ 2655.371972] 0000000000000001 ffff880600000001 ffffffff876c2060 0000000000000009
[ 2655.371972] Call Trace:
[ 2655.371972] [<lib/dump_stack.c:52>] dump_stack+0x52/0x7f
[ 2655.371972] [<kernel/locking/lockdep.c:2254>] print_usage_bug+0x1a7/0x1e0
[ 2655.371972] [<kernel/locking/lockdep.c:2347>] ? print_usage_bug+0x1e0/0x1e0
[ 2655.371972] [<kernel/locking/lockdep.c:2465>] mark_lock_irq+0xd9/0x2a0
[ 2655.371972] [<kernel/locking/lockdep.c:2920>] mark_lock+0x128/0x210
[ 2655.371972] [<kernel/locking/lockdep.c:2821>] mark_irqflags+0x144/0x170
[ 2655.371972] [<kernel/locking/lockdep.c:3138>] __lock_acquire+0x2de/0x5a0
[ 2655.371972] [<arch/x86/include/asm/current.h:14 kernel/locking/lockdep.c:3602>] lock_acquire+0x182/0x1d0
[ 2655.371972] [<drivers/block/zram/zram_drv.c:663>] ? zram_make_request+0x2a/0xc0
[ 2655.371972] [<arch/x86/include/asm/rwsem.h:83 kernel/locking/rwsem.c:23>] down_read+0x47/0xa0
[ 2655.371972] [<drivers/block/zram/zram_drv.c:663>] ? zram_make_request+0x2a/0xc0
[ 2655.371972] [<arch/x86/include/asm/current.h:14 kernel/sched/core.c:2508>] ? preempt_count_add+0x96/0xc0
[ 2655.371972] [<drivers/block/zram/zram_drv.c:663>] zram_make_request+0x2a/0xc0
[ 2655.371972] [<block/blk-core.c:1862>] generic_make_request+0xb6/0x110
[ 2655.371972] [<block/blk-core.c:1913>] submit_bio+0x148/0x170
[ 2655.371972] [<include/linux/rcupdate.h:800 include/linux/memcontrol.h:180 mm/page-writeback.c:2408>] ? test_set_page_writeback+0x24e/0x2a0
[ 2655.371972] [<mm/page_io.c:315>] __swap_writepage+0x1fc/0x220
[ 2655.371972] [<arch/x86/include/asm/preempt.h:98 include/linux/spinlock_api_smp.h:152 kernel/locking/spinlock.c:183>] ? _raw_spin_unlock+0x30/0x50
[ 2655.371972] [<mm/swapfile.c:898>] ? page_swapcount+0x4e/0x60
[ 2655.371972] [<mm/page_io.c:249>] swap_writepage+0x72/0x80
[ 2655.371972] [<mm/vmscan.c:502>] pageout+0x167/0x2e0
[ 2655.371972] [<mm/vmscan.c:1015>] shrink_page_list+0x4f4/0x7c0
[ 2655.371972] [<include/linux/spinlock.h:328 mm/vmscan.c:1503>] shrink_inactive_list+0x31c/0x570
[ 2655.371972] [<mm/vmscan.c:1744>] ? shrink_active_list+0x30b/0x320
[ 2655.371972] [<mm/vmscan.c:1830 mm/vmscan.c:2054>] shrink_lruvec+0x124/0x300
[ 2655.371972] [<arch/x86/include/asm/paravirt.h:192 arch/x86/kernel/tsc.c:305>] ? sched_clock+0x1d/0x30
[ 2655.371972] [<mm/vmscan.c:2235>] shrink_zone+0x8e/0x1d0
[ 2655.371972] [<include/linux/bitmap.h:165 include/linux/nodemask.h:131 mm/vmscan.c:2904>] kswapd_shrink_zone+0xf1/0x1b0
[ 2655.371972] [<mm/vmscan.c:3088>] balance_pgdat+0x363/0x540
[ 2655.371972] [<kernel/sched/wait.c:254>] ? finish_wait+0x70/0x90
[ 2655.371972] [<mm/vmscan.c:3296>] kswapd+0x2eb/0x350
[ 2655.371972] [<mm/vmscan.c:3213>] ? ftrace_raw_event_mm_vmscan_writepage+0x180/0x180
[ 2655.371972] [<kernel/kthread.c:216>] kthread+0x105/0x110
[ 2655.371972] [<kernel/locking/lockdep.c:3506>] ? __lock_release+0x1e2/0x200
[ 2655.371972] [<kernel/kthread.c:185>] ? set_kthreadd_affinity+0x30/0x30
[ 2655.371972] [<arch/x86/kernel/entry_64.S:555>] ret_from_fork+0x7c/0xb0
[ 2655.371972] [<kernel/kthread.c:185>] ? set_kthreadd_affinity+0x30/0x30

Thanks,
Sasha
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Next message: David Herrmann: "[PATCH 3/4] ath6kl: set NET_NAME_USER for P2P ifs"
Previous message: Guillaume Morin: "Re: + exitc-call-proc_exit_connector-after-exit_state-is-set.patch added to -mm tree"
Next in thread: Minchan Kim: "Re: zram: lockdep spew for zram->init_lock"
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