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IRQ Lock Inversion dependency detected?

To: xfs@xxxxxxxxxxx
Subject: IRQ Lock Inversion dependency detected?
From: Andrew Ryder <tireman@xxxxxxx>
Date: Sat, 20 Aug 2016 00:09:24 -0400
Delivered-to: xfs@xxxxxxxxxxx
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Had this pop up sometime in the last 24 hours but it didn't seem to cause me any problems? Thought I'd pass it along if its of use or ignore them in the future? I've attached the full dmesg output also.

[20653.098044] =========================================================
[20653.098044] [ INFO: possible irq lock inversion dependency detected ]
[20653.098044] 3.19.8 #6 Tainted: G           O
[20653.098044] ---------------------------------------------------------
[20653.098044] kswapd0/513 just changed the state of lock:
[20653.098044] (&xfs_dir_ilock_class){++++-+}, at: [<ffffffff812f4360>] xfs_ilock+0xb0/0x130 [20653.098044] but this lock took another, RECLAIM_FS-unsafe lock in the past:
[20653.098044]  (&mm->mmap_sem){++++++}

and interrupts could create inverse lock ordering between them.

[20653.098044]
               other info that might help us debug this:
[20653.098044]  Possible interrupt unsafe locking scenario:

[20653.098044]        CPU0                    CPU1
[20653.098044]        ----                    ----
[20653.098044]   lock(&mm->mmap_sem);
[20653.098044]                                local_irq_disable();
[20653.098044]                                lock(&xfs_dir_ilock_class);
[20653.098044]                                lock(&mm->mmap_sem);
[20653.098044]   <Interrupt>
[20653.098044]     lock(&xfs_dir_ilock_class);
[20653.098044]
                *** DEADLOCK ***

[20653.098044] 3 locks held by kswapd0/513:
[20653.098044] #0: (shrinker_rwsem){++++..}, at: [<ffffffff811303d3>] shrink_node_slabs+0x43/0x3b0 [20653.098044] #1: (&type->s_umount_key#36){.+.+.+}, at: [<ffffffff8117b98f>] grab_super_passive+0x3f/0x90 [20653.098044] #2: (&pag->pag_ici_reclaim_lock){+.+...}, at: [<ffffffff812eca52>] xfs_reclaim_inodes_ag+0xa2/0x3c0
[20653.214021]
               the shortest dependencies between 2nd lock and 1st lock:
[20653.214021]  -> (&mm->mmap_sem){++++++} ops: 1132789158 {
[20653.214021]     HARDIRQ-ON-W at:
[20653.214021] [<ffffffff81092c43>] __lock_acquire+0x9a3/0x2090 [20653.214021] [<ffffffff81095323>] lock_acquire+0xc3/0x170 [20653.214021] [<ffffffff816d98c5>] down_write+0x55/0xc0 [20653.214021] [<ffffffff8117fb50>] do_execveat_common.isra.33+0x2e0/0x7a0

Attachment: aug20_dmes_xfs_irq
Description: Text document

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