[linux-mmotm] i915_gem_userptr_get_pages: possible circular locking dependency detected

[Sergey Senozhatsky]

Hello,

[  530.698622] ======================================================
[  530.698623] WARNING: possible circular locking dependency detected
[  530.698626] 4.11.0-rc2-mm1-dbg-00167-gdb8a9941614c-dirty #222 Not tainted
[  530.698627] ------------------------------------------------------
[  530.698628] Xorg/343 is trying to acquire lock:
[  530.698630]  (&mm->mmap_sem){++++++}, at: [<ffffffffa057e085>] i915_gem_userptr_get_pages+0x60/0x29c [i915]
[  530.698702] 
               but task is already holding lock:
[  530.698703]  (&obj->mm.lock){+.+.+.}, at: [<ffffffffa0572d78>] __i915_gem_object_get_pages+0x21/0x62 [i915]
[  530.698763] 
               which lock already depends on the new lock.

[  530.698764] 
               the existing dependency chain (in reverse order) is:
[  530.698766] 
               -> #1 (&obj->mm.lock){+.+.+.}:
[  530.698779]        lock_acquire+0x130/0x1c4
[  530.698822]        i915_gem_fault+0x138/0x531 [i915]
[  530.698826]        __do_fault+0x1e/0xb4
[  530.698831]        __handle_mm_fault+0x897/0xe37
[  530.698834]        handle_mm_fault+0x93/0xd2
[  530.698839]        __do_page_fault+0x20c/0x3db
[  530.698843]        do_page_fault+0xc/0xe
[  530.698848]        page_fault+0x22/0x30
[  530.698849] 
               -> #0 (&mm->mmap_sem){++++++}:
[  530.698858]        __lock_acquire+0xf49/0x1548
[  530.698861]        lock_acquire+0x130/0x1c4
[  530.698866]        down_read+0x3e/0x62
[  530.698910]        i915_gem_userptr_get_pages+0x60/0x29c [i915]
[  530.698951]        ____i915_gem_object_get_pages+0x3f/0x57 [i915]
[  530.698993]        __i915_gem_object_get_pages+0x41/0x62 [i915]
[  530.699035]        i915_gem_set_domain_ioctl+0x1f6/0x2b0 [i915]
[  530.699057]        drm_ioctl+0x248/0x363 [drm]
[  530.699061]        vfs_ioctl+0x18/0x34
[  530.699064]        do_vfs_ioctl+0x5a2/0x64d
[  530.699067]        SyS_ioctl+0x43/0x61
[  530.699070]        entry_SYSCALL_64_fastpath+0x18/0xad
[  530.699072] 
               other info that might help us debug this:

[  530.699073]  Possible unsafe locking scenario:

[  530.699075]        CPU0                    CPU1
[  530.699076]        ----                    ----
[  530.699077]   lock(&obj->mm.lock);
[  530.699081]                                lock(&mm->mmap_sem);
[  530.699084]                                lock(&obj->mm.lock);
[  530.699087]   lock(&mm->mmap_sem);
[  530.699090] 
                *** DEADLOCK ***

[  530.699092] 1 lock held by Xorg/343:
[  530.699094]  #0:  (&obj->mm.lock){+.+.+.}, at: [<ffffffffa0572d78>] __i915_gem_object_get_pages+0x21/0x62 [i915]
[  530.699141] 
               stack backtrace:
[  530.699144] CPU: 6 PID: 343 Comm: Xorg Not tainted 4.11.0-rc2-mm1-dbg-00167-gdb8a9941614c-dirty #222
[  530.699146] Call Trace:
[  530.699152]  dump_stack+0x68/0x92
[  530.699158]  print_circular_bug+0x286/0x294
[  530.699163]  __lock_acquire+0xf49/0x1548
[  530.699168]  ? lock_acquire+0x130/0x1c4
[  530.699173]  lock_acquire+0x130/0x1c4
[  530.699177]  ? lock_acquire+0x130/0x1c4
[  530.699223]  ? i915_gem_userptr_get_pages+0x60/0x29c [i915]
[  530.699228]  down_read+0x3e/0x62
[  530.699273]  ? i915_gem_userptr_get_pages+0x60/0x29c [i915]
[  530.699318]  i915_gem_userptr_get_pages+0x60/0x29c [i915]
[  530.699361]  ____i915_gem_object_get_pages+0x3f/0x57 [i915]
[  530.699403]  __i915_gem_object_get_pages+0x41/0x62 [i915]
[  530.699446]  i915_gem_set_domain_ioctl+0x1f6/0x2b0 [i915]
[  530.699463]  drm_ioctl+0x248/0x363 [drm]
[  530.699506]  ? i915_gem_obj_prepare_shmem_write+0x1ba/0x1ba [i915]
[  530.699511]  vfs_ioctl+0x18/0x34
[  530.699514]  do_vfs_ioctl+0x5a2/0x64d
[  530.699517]  ? __fget+0x182/0x194
[  530.699521]  SyS_ioctl+0x43/0x61
[  530.699524]  entry_SYSCALL_64_fastpath+0x18/0xad
[  530.699527] RIP: 0033:0x7fa1bb3150d7
[  530.699529] RSP: 002b:00007ffe1f1fbc48 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
[  530.699534] RAX: ffffffffffffffda RBX: 00000000e0000000 RCX: 00007fa1bb3150d7
[  530.699536] RDX: 00007ffe1f1fbc70 RSI: 00000000400c645f RDI: 000000000000000b
[  530.699538] RBP: 00000000a1fcd537 R08: 00000000000000ff R09: 0000000001c564d8
[  530.699540] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000015
[  530.699542] R13: 0000000001c474b0 R14: 00000000000001f2 R15: 0000000001c43488


	-ss