BSW GEN9: Few tests - WARNING: possible circular locking dependency detected is trying to acquire lock:. at: stop_machine. but task is already holding lock at: do_page_fault

https://intel-gfx-ci.01.org/tree/drm-tip/drmtip_465/fi-apl-guc/igt@kms_plane@pixel-format-pipe-a-planes.html

4> [70.541024] ======================================================
<4> [70.541028] WARNING: possible circular locking dependency detected
<4> [70.541035] 5.6.0-rc7-g68b152390f91-drmtip_465+ #1 Tainted: G     U           
<4> [70.541038] ------------------------------------------------------
<4> [70.541043] kms_plane/2040 is trying to acquire lock:
<4> [70.541048] ffffffff8543dc10 (cpu_hotplug_lock.rw_sem){++++}, at: stop_machine+0x12/0x30
<4> [70.541062] 
but task is already holding lock:
<4> [70.541066] ffff9fe6365626d8 (&mm->mmap_sem#2){++++}, at: do_page_fault+0x13a/0x6f0
<4> [70.541077] 
which lock already depends on the new lock.
<4> [70.541081] 
the existing dependency chain (in reverse order) is:
<4> [70.541085] 
-> #3 (&mm->mmap_sem#2){++++}:
<4> [70.541097]        __might_fault+0x63/0x90
<4> [70.541104]        _copy_to_user+0x1e/0x80
<4> [70.541110]        perf_read+0x200/0x2b0
<4> [70.541116]        vfs_read+0x96/0x160
<4> [70.541121]        ksys_read+0x9f/0xe0
<4> [70.541127]        do_syscall_64+0x4f/0x240
<4> [70.541136]        entry_SYSCALL_64_after_hwframe+0x49/0xbe
<4> [70.541139] 
-> #2 (&cpuctx_mutex){+.+.}:
<4> [70.541149]        __mutex_lock+0x9a/0x9c0
<4> [70.541155]        perf_event_init_cpu+0xa4/0x140
<4> [70.541162]        perf_event_init+0x1c9/0x1f9
<4> [70.541168]        start_kernel+0x362/0x4eb
<4> [70.541173]        secondary_startup_64+0xb6/0xc0
<4> [70.541177] 
-> #1 (pmus_lock){+.+.}:
<4> [70.541185]        __mutex_lock+0x9a/0x9c0
<4> [70.541191]        perf_event_init_cpu+0x6b/0x140
<4> [70.541198]        cpuhp_invoke_callback+0x9b/0x9d0
<4> [70.541203]        _cpu_up+0xa2/0x140
<4> [70.541208]        do_cpu_up+0x61/0xa0
<4> [70.541215]        smp_init+0x57/0x96
<4> [70.541220]        kernel_init_freeable+0x87/0x1dc
<4> [70.541225]        kernel_init+0x5/0x100
<4> [70.541231]        ret_from_fork+0x3a/0x50
<4> [70.541234] 
-> #0 (cpu_hotplug_lock.rw_sem){++++}:
<4> [70.541245]        __lock_acquire+0x1328/0x15d0
<4> [70.541250]        lock_acquire+0xa7/0x1c0
<4> [70.541255]        cpus_read_lock+0x34/0xd0
<4> [70.541260]        stop_machine+0x12/0x30
<4> [70.541460]        bxt_vtd_ggtt_insert_entries__BKL+0x36/0x50 [i915]
<4> [70.541634]        ggtt_bind_vma+0x31/0x50 [i915]
<4> [70.541835]        __vma_bind+0x26/0x40 [i915]
<4> [70.542001]        fence_work+0x1c/0x88 [i915]
<4> [70.542166]        fence_notify+0x78/0xf8 [i915]
<4> [70.542331]        __i915_sw_fence_complete+0x81/0x250 [i915]
<4> [70.542530]        i915_vma_pin+0x21e/0x1190 [i915]
<4> [70.542727]        i915_gem_object_ggtt_pin+0xb0/0x270 [i915]
<4> [70.542920]        vm_fault_gtt+0x12f/0x990 [i915]
<4> [70.542927]        __do_fault+0x45/0xf8
<4> [70.542934]        __handle_mm_fault+0xba9/0x10c0
<4> [70.542940]        handle_mm_fault+0x154/0x340
<4> [70.542946]        do_page_fault+0x3ca/0x6f0
<4> [70.542951]        page_fault+0x34/0x40
<4> [70.542954] 
other info that might help us debug this:
<4> [70.542958] Chain exists of:
  cpu_hotplug_lock.rw_sem --> &cpuctx_mutex --> &mm->mmap_sem#2
<4> [70.542966]  Possible unsafe locking scenario:
<4> [70.542970]        CPU0                    CPU1
<4> [70.542973]        ----                    ----
<4> [70.542976]   lock(&mm->mmap_sem#2);
<4> [70.542981]                                lock(&cpuctx_mutex);
<4> [70.542985]                                lock(&mm->mmap_sem#2);
<4> [70.542990]   lock(cpu_hotplug_lock.rw_sem);
<4> [70.542995] 
 *** DEADLOCK ***
````