Patch bd36d3bab2 fixed a deadlock in the
failure path of drm_lease_create. This made the partially initialized
lease object visible for a short window of time.
To avoid having the lessee state appear transiently, I've rearranged
the code so that the lessor fields are not filled in until the
parameters are all validated and the function will succeed.
Signed-off-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20171221065424.1304-1-keithp@keithp.com
This case can been seen when creating the lease with the same objects passed.
[ 605.515097] 2 locks held by testapp/3337:
[ 605.519027] #0: (&dev->mode_config.idr_mutex){......}, at: [<ffff0000085f1664>] drm_mode_create_lease_ioctl+0x384/0x858
[ 605.530045] #1: (&dev->mode_config.idr_mutex){......}, at: [<ffff0000085f11bc>] drm_lease_destroy+0x2c/0x110
Which was causing the process to hang:
[ 605.398827] [<ffff0000080856cc>] __switch_to+0x94/0xa8
[ 605.404030] [<ffff000008c05d00>] __schedule+0x1b0/0x698
[ 605.409322] [<ffff000008c06224>] schedule+0x3c/0xa8
[ 605.414260] [<ffff000008c06628>] schedule_preempt_disabled+0x20/0x38
[ 605.420677] [<ffff000008c07370>] mutex_lock_nested+0x158/0x340
[ 605.426572] [<ffff0000085f11bc>] drm_lease_destroy+0x2c/0x110
[ 605.432389] [<ffff0000085cecf0>] drm_master_put+0xc0/0xc8
[ 605.437845] [<ffff0000085f175c>] drm_mode_create_lease_ioctl+0x47c/0x858
[ 605.444612] [<ffff0000085d4460>] drm_ioctl+0x198/0x448
[ 605.449811] [<ffff000008201134>] do_vfs_ioctl+0xa4/0x748
[ 605.455192] [<ffff000008201864>] SyS_ioctl+0x8c/0xa0
[ 605.460216] [<ffff000008082f4c>] __sys_trace_return+0x0/0x4
drm_mode_create_lease_ioctl() calls drm_lease_create() which acquires a lock
on dev->mode_config.idr_mutex. In case of failure, drm_lease_create() calls
drm_master_put() which in turn tries to acquire the same lock when calling
drm_lease_destroy().
v2: - Reverse the order at exit in case of fail, so that unlocking takes place
before dropping the reference.
- Include detail information about deadlock (Daniel Vetter)
Signed-off-by: Marius Vlad <marius-cristian.vlad@nxp.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20171213181048.32719-1-marius-cristian.vlad@nxp.com
drm_mode_create_lease
Creates a lease for a list of drm mode objects, returning an
fd for the new drm_master and a 64-bit identifier for the lessee
drm_mode_list_lesees
List the identifiers of the lessees for a master file
drm_mode_get_lease
List the leased objects for a master file
drm_mode_revoke_lease
Erase the set of objects managed by a lease.
This should suffice to at least create and query leases.
Changes for v2 as suggested by Daniel Vetter <daniel.vetter@ffwll.ch>:
* query ioctls only query the master associated with
the provided file.
* 'mask_lease' value has been removed
* change ioctl has been removed.
Changes for v3 suggested in part by Dave Airlie <airlied@gmail.com>
* Add revoke ioctl.
Changes for v4 suggested by Dave Airlie <airlied@gmail.com>
* Expand on the comment about the magic use of &drm_lease_idr_object
* Pad lease ioctl structures to align on 64-bit boundaries
Changes for v5 suggested by Dave Airlie <airlied@gmail.com>
* Check for non-negative object_id in create_lease to avoid debug
output from the kernel.
Changes for v6 provided by Dave Airlie <airlied@gmail.com>
* For non-universal planes add primary/cursor planes to lease
If we aren't exposing universal planes to this userspace client,
and it requests a lease on a crtc, we should implicitly export the
primary and cursor planes for the crtc.
If the lessee doesn't request universal planes, it will just see
the crtc, but if it does request them it will then see the plane
objects as well.
This also moves the object look ups earlier as a side effect, so
we'd exit the ioctl quicker for non-existant objects.
* Restrict leases to crtc/connector/planes.
This only allows leasing for objects we wish to allow.
Changes for v7 provided by Dave Airlie <airlied@gmail.com>
* Check pad args are 0
* Check create flags and object count are valid.
* Check return from fd allocation
* Refactor lease idr setup and add some simple validation
* Use idr_mutex uniformly (Keith)
Signed-off-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
This provides new data structures to hold "lease" information about
drm mode setting objects, and provides for creating new drm_masters
which have access to a subset of the available drm resources.
An 'owner' is a drm_master which is not leasing the objects from
another drm_master, and hence 'owns' them.
A 'lessee' is a drm_master which is leasing objects from some other
drm_master. Each lessee holds the set of objects which it is leasing
from the lessor.
A 'lessor' is a drm_master which is leasing objects to another
drm_master. This is the same as the owner in the current code.
The set of objects any drm_master 'controls' is limited to the set of
objects it leases (for lessees) or all objects (for owners).
Objects not controlled by a drm_master cannot be modified through the
various state manipulating ioctls, and any state reported back to user
space will be edited to make them appear idle and/or unusable. For
instance, connectors always report 'disconnected', while encoders
report no possible crtcs or clones.
The full list of lessees leasing objects from an owner (either
directly, or indirectly through another lessee), can be searched from
an idr in the drm_master of the owner.
Changes for v2 as suggested by Daniel Vetter <daniel.vetter@ffwll.ch>:
* Sub-leasing has been disabled.
* BUG_ON for lock checking replaced with lockdep_assert_held
* 'change' ioctl has been removed.
* Leased objects can always be controlled by the lessor; the
'mask_lease' flag has been removed
* Checking for leased status has been simplified, replacing
the drm_lease_check function with drm_lease_held.
Changes in v3, some suggested by Dave Airlie <airlied@gmail.com>
* Add revocation. This allows leases to be effectively revoked by
removing all of the objects they have access to. The lease itself
hangs around as it's hanging off a file.
* Free the leases IDR when the master is destroyed
* _drm_lease_held should look at lessees, not lessor
* Allow non-master files to check for lease status
Changes in v4, suggested by Dave Airlie <airlied@gmail.com>
* Formatting and whitespace changes
Changes in v5 (airlied)
* check DRIVER_MODESET before lease destroy call
* check DRIVER_MODESET for lease revoke (Chris)
* Use idr_mutex uniformly for all lease elements of struct drm_master. (Keith)
Signed-off-by: Keith Packard <keithp@keithp.com>
Keith Packard