Bug 110528

https://intel-gfx-ci.01.org/tree/drm-tip/drmtip_261/fi-pnv-d510/igt@gem_userptr_blits@coherency-sync.html

	
<6> [138.626463] Console: switching to colour dummy device 80x25
<6> [138.626818] [IGT] gem_userptr_blits: executing
<6> [138.696844] [IGT] gem_userptr_blits: starting subtest coherency-sync
<6> [138.698192] gem_userptr_bli (2136): drop_caches: 4
<4> [162.324467] 
<4> [162.324494] ======================================================
<4> [162.324509] WARNING: possible circular locking dependency detected
<4> [162.324527] 5.1.0-rc5-g9b6a59cae931-drmtip_261+ #1 Tainted: G     U           
<4> [162.324543] ------------------------------------------------------
<4> [162.324557] kswapd0/50 is trying to acquire lock:
<4> [162.324572] 00000000cdcc63cb (&dev->struct_mutex/1){+.+.}, at: userptr_mn_invalidate_range_start+0x173/0x270 [i915]
<4> [162.324779] 
but task is already holding lock:
<4> [162.324794] 000000005d3bddaa (&anon_vma->rwsem){++++}, at: page_lock_anon_vma_read+0xe6/0x2a0
<4> [162.324822] 
which lock already depends on the new lock.

<4> [162.324839] 
the existing dependency chain (in reverse order) is:
<4> [162.324854] 
-> #2 (&anon_vma->rwsem){++++}:
<4> [162.324875]        down_write+0x33/0x60
<4> [162.324888]        __vma_adjust+0x390/0x6c0
<4> [162.324904]        __split_vma+0x16a/0x180
<4> [162.324918]        mprotect_fixup+0x2a5/0x320
<4> [162.324932]        do_mprotect_pkey+0x208/0x2e0
<4> [162.324947]        __x64_sys_mprotect+0x16/0x20
<4> [162.324962]        do_syscall_64+0x55/0x190
<4> [162.324977]        entry_SYSCALL_64_after_hwframe+0x49/0xbe
<4> [162.324991] 
-> #1 (&mapping->i_mmap_rwsem){++++}:
<4> [162.325012]        down_write+0x33/0x60
<4> [162.325027]        unmap_mapping_pages+0x48/0x130
<4> [162.325215]        i915_vma_revoke_mmap+0x7e/0x1c0 [i915]
<4> [162.325237]        i915_vma_unbind+0xbb/0x550 [i915]
<4> [162.325237]        i915_gem_object_unbind+0xfa/0x190 [i915]
<4> [162.325237]        i915_gem_shrink+0x2dc/0x590 [i915]
<4> [162.325237]        i915_gem_shrink_all+0x2c/0x50 [i915]
<4> [162.325237]        i915_drop_caches_set+0x1b6/0x270 [i915]
<4> [162.325237]        simple_attr_write+0xb0/0xd0
<4> [162.325237]        full_proxy_write+0x51/0x80
<4> [162.325237]        vfs_write+0xbd/0x1b0
<4> [162.325237]        ksys_write+0x55/0xe0
<4> [162.325237]        do_syscall_64+0x55/0x190
<4> [162.325237]        entry_SYSCALL_64_after_hwframe+0x49/0xbe
<4> [162.325237] 
-> #0 (&dev->struct_mutex/1){+.+.}:
<4> [162.325237]        lock_acquire+0xa6/0x1c0
<4> [162.325237]        __mutex_lock+0x8c/0x960
<4> [162.325237]        userptr_mn_invalidate_range_start+0x173/0x270 [i915]
<4> [162.325237]        __mmu_notifier_invalidate_range_start+0x84/0x110
<4> [162.325237]        try_to_unmap_one+0x747/0x840
<4> [162.325237]        rmap_walk_anon+0x104/0x280
<4> [162.325237]        try_to_unmap+0xc0/0xf0
<4> [162.325237]        shrink_page_list+0x5ce/0xcb0
<4> [162.325237]        shrink_inactive_list+0x331/0x710
<4> [162.325237]        shrink_node_memcg+0x37b/0x770
<4> [162.325237]        shrink_node+0xc9/0x460
<4> [162.325237]        balance_pgdat+0x239/0x580
<4> [162.325237]        kswapd+0x186/0x570
<4> [162.325237]        kthread+0x119/0x130
<4> [162.325237]        ret_from_fork+0x24/0x50
<4> [162.325237] 
other info that might help us debug this:

<4> [162.325237] Chain exists of:
  &dev->struct_mutex/1 --> &mapping->i_mmap_rwsem --> &anon_vma->rwsem

<4> [162.325237]  Possible unsafe locking scenario:

<4> [162.325237]        CPU0                    CPU1
<4> [162.325237]        ----                    ----
<4> [162.325237]   lock(&anon_vma->rwsem);
<4> [162.325237]                                lock(&mapping->i_mmap_rwsem);
<4> [162.325237]                                lock(&anon_vma->rwsem);
<4> [162.325237]   lock(&dev->struct_mutex/1);
<4> [162.325237] 
 *** DEADLOCK ***