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Daniel Vetter uncovered a nasty cycle in using the mmu-notifiers to
invalidate userptr objects which also happen to be pulled into GGTT
mmaps. That is when we unbind the userptr object (on mmu invalidation),
we revoke all CPU mmaps, which may then recurse into mmu invalidation.
We looked for ways of breaking the cycle, but the revocation on
invalidation is required and cannot be avoided. The only solution we
could see was to not allow such GGTT bindings of userptr objects in the
first place. In practice, no one really wants to use a GGTT mmapping of
a CPU pointer...
Just before Daniel's explosive lockdep patches land in v5.4-rc1, we got
a genuine blip from CI:
<4>[ 246.793958] ======================================================
<4>[ 246.793972] WARNING: possible circular locking dependency detected
<4>[ 246.793989] 5.3.0-gbd6c56f50d15-drmtip_372+ #1 Tainted: G U
<4>[ 246.794003] ------------------------------------------------------
<4>[ 246.794017] kswapd0/145 is trying to acquire lock:
<4>[ 246.794030] 000000003f565be6 (&dev->struct_mutex/1){+.+.}, at: userptr_mn_invalidate_range_start+0x18f/0x220 [i915]
<4>[ 246.794250]
but task is already holding lock:
<4>[ 246.794263] 000000001799cef9 (&anon_vma->rwsem){++++}, at: page_lock_anon_vma_read+0xe6/0x2a0
<4>[ 246.794291]
which lock already depends on the new lock.
<4>[ 246.794307]
the existing dependency chain (in reverse order) is:
<4>[ 246.794322]
-> #3 (&anon_vma->rwsem){++++}:
<4>[ 246.794344] down_write+0x33/0x70
<4>[ 246.794357] __vma_adjust+0x3d9/0x7b0
<4>[ 246.794370] __split_vma+0x16a/0x180
<4>[ 246.794385] mprotect_fixup+0x2a5/0x320
<4>[ 246.794399] do_mprotect_pkey+0x208/0x2e0
<4>[ 246.794413] __x64_sys_mprotect+0x16/0x20
<4>[ 246.794429] do_syscall_64+0x55/0x1c0
<4>[ 246.794443] entry_SYSCALL_64_after_hwframe+0x49/0xbe
<4>[ 246.794456]
-> #2 (&mapping->i_mmap_rwsem){++++}:
<4>[ 246.794478] down_write+0x33/0x70
<4>[ 246.794493] unmap_mapping_pages+0x48/0x130
<4>[ 246.794519] i915_vma_revoke_mmap+0x81/0x1b0 [i915]
<4>[ 246.794519] i915_vma_unbind+0x11d/0x4a0 [i915]
<4>[ 246.794519] i915_vma_destroy+0x31/0x300 [i915]
<4>[ 246.794519] __i915_gem_free_objects+0xb8/0x4b0 [i915]
<4>[ 246.794519] drm_file_free.part.0+0x1e6/0x290
<4>[ 246.794519] drm_release+0xa6/0xe0
<4>[ 246.794519] __fput+0xc2/0x250
<4>[ 246.794519] task_work_run+0x82/0xb0
<4>[ 246.794519] do_exit+0x35b/0xdb0
<4>[ 246.794519] do_group_exit+0x34/0xb0
<4>[ 246.794519] __x64_sys_exit_group+0xf/0x10
<4>[ 246.794519] do_syscall_64+0x55/0x1c0
<4>[ 246.794519] entry_SYSCALL_64_after_hwframe+0x49/0xbe
<4>[ 246.794519]
-> #1 (&vm->mutex){+.+.}:
<4>[ 246.794519] i915_gem_shrinker_taints_mutex+0x6d/0xe0 [i915]
<4>[ 246.794519] i915_address_space_init+0x9f/0x160 [i915]
<4>[ 246.794519] i915_ggtt_init_hw+0x55/0x170 [i915]
<4>[ 246.794519] i915_driver_probe+0xc9f/0x1620 [i915]
<4>[ 246.794519] i915_pci_probe+0x43/0x1b0 [i915]
<4>[ 246.794519] pci_device_probe+0x9e/0x120
<4>[ 246.794519] really_probe+0xea/0x3d0
<4>[ 246.794519] driver_probe_device+0x10b/0x120
<4>[ 246.794519] device_driver_attach+0x4a/0x50
<4>[ 246.794519] __driver_attach+0x97/0x130
<4>[ 246.794519] bus_for_each_dev+0x74/0xc0
<4>[ 246.794519] bus_add_driver+0x13f/0x210
<4>[ 246.794519] driver_register+0x56/0xe0
<4>[ 246.794519] do_one_initcall+0x58/0x300
<4>[ 246.794519] do_init_module+0x56/0x1f6
<4>[ 246.794519] load_module+0x25bd/0x2a40
<4>[ 246.794519] __se_sys_finit_module+0xd3/0xf0
<4>[ 246.794519] do_syscall_64+0x55/0x1c0
<4>[ 246.794519] entry_SYSCALL_64_after_hwframe+0x49/0xbe
<4>[ 246.794519]
-> #0 (&dev->struct_mutex/1){+.+.}:
<4>[ 246.794519] __lock_acquire+0x15d8/0x1e90
<4>[ 246.794519] lock_acquire+0xa6/0x1c0
<4>[ 246.794519] __mutex_lock+0x9d/0x9b0
<4>[ 246.794519] userptr_mn_invalidate_range_start+0x18f/0x220 [i915]
<4>[ 246.794519] __mmu_notifier_invalidate_range_start+0x85/0x110
<4>[ 246.794519] try_to_unmap_one+0x76b/0x860
<4>[ 246.794519] rmap_walk_anon+0x104/0x280
<4>[ 246.794519] try_to_unmap+0xc0/0xf0
<4>[ 246.794519] shrink_page_list+0x561/0xc10
<4>[ 246.794519] shrink_inactive_list+0x220/0x440
<4>[ 246.794519] shrink_node_memcg+0x36e/0x740
<4>[ 246.794519] shrink_node+0xcb/0x490
<4>[ 246.794519] balance_pgdat+0x241/0x580
<4>[ 246.794519] kswapd+0x16c/0x530
<4>[ 246.794519] kthread+0x119/0x130
<4>[ 246.794519] ret_from_fork+0x24/0x50
<4>[ 246.794519]
other info that might help us debug this:
<4>[ 246.794519] Chain exists of:
&dev->struct_mutex/1 --> &mapping->i_mmap_rwsem --> &anon_vma->rwsem
<4>[ 246.794519] Possible unsafe locking scenario:
<4>[ 246.794519] CPU0 CPU1
<4>[ 246.794519] ---- ----
<4>[ 246.794519] lock(&anon_vma->rwsem);
<4>[ 246.794519] lock(&mapping->i_mmap_rwsem);
<4>[ 246.794519] lock(&anon_vma->rwsem);
<4>[ 246.794519] lock(&dev->struct_mutex/1);
<4>[ 246.794519]
*** DEADLOCK ***
v2: Say no to mmap_ioctl
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=111744
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=111870
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: stable@vger.kernel.org
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190928082546.3473-1-chris@chris-wilson.co.uk
(cherry picked from commit a4311745bba9763e3c965643d4531bd5765b0513)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
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Move the active tracking for the frontbuffer operations out of the
i915_gem_object and into its own first class (refcounted) object. In the
process of detangling, we switch from low level request tracking to the
easier i915_active -- with the plan that this avoids any potential
atomic callbacks as the frontbuffer tracking wishes to sleep as it
flushes.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190816074635.26062-1-chris@chris-wilson.co.uk
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Switch to tracking activity via i915_active on individual nodes, only
keeping a list of retired objects in the cache, and reaping the cache
when the engine itself idles.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190804124826.30272-2-chris@chris-wilson.co.uk
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Remove the accumulated optimisations that we have for i915_vma_retire
and reduce it to the bare essential of tracking the active object
reference. This allows us to only use atomic operations, and so will be
able to avoid the struct_mutex requirement.
The principal loss here is the shrinker MRU bumping, so now if we have
to shrink, we will do so in much more random order and more likely to
try and shrink recently used objects. That is a nuisance, but shrinking
active objects is a second step we try to avoid and will always be a
system-wide performance issue.
The other loss is here is in the automatic pruning of the
reservation_object when idling. This is not as large an issue as upon
reservation_object introduction as now adding new fences into the object
replaces already signaled fences, keeping the array compact. But we do
lose the auto-expiration of stale fences and unused arrays. That may be
a noticeable problem for which we need to re-implement autopruning.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190621183801.23252-3-chris@chris-wilson.co.uk
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Since commit 1ba627148ef5 ("drm: Add reservation_object to
drm_gem_object"), struct drm_gem_object grew its own builtin
reservation_object rendering our own private one bloat. Remove our
redundant reservation_object and point into obj->base.resv instead.
References: 1ba627148ef5 ("drm: Add reservation_object to drm_gem_object")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190618125858.7295-1-chris@chris-wilson.co.uk
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With async binding, we don't want to manage a bound/unbound list as we
may end up running before we even acquire the pages. All that is
required is keeping track of shrinkable objects, so reduce it to the
minimum list.
Fixes: 6951e5893b48 ("drm/i915: Move GEM object domain management from struct_mutex to local")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Matthew Auld <matthew.william.auld@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190612105720.30310-1-chris@chris-wilson.co.uk
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Use i915_gem_object_lock() to guard the LUT and active reference to
allow us to break free of struct_mutex for handling GEM_CLOSE.
Testcase: igt/gem_close_race
Testcase: igt/gem_exec_parallel
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190606112320.9704-1-chris@chris-wilson.co.uk
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An old optimisation to reduce the number of atomics per batch sadly
relies on struct_mutex for coordination. In order to remove struct_mutex
from serialising object/context closing, always taking and releasing an
active reference on first use / last use greatly simplifies the locking.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190528092956.14910-15-chris@chris-wilson.co.uk
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Continuing the decluttering of i915_gem.c, this time the legacy physical
object.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190528092956.14910-5-chris@chris-wilson.co.uk
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For convenience in avoiding inline spaghetti, keep the type definition
as a separate header.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Acked-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190528092956.14910-1-chris@chris-wilson.co.uk
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