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drm/i915: Prevent recursive deadlock on releasing a busy userptr 

During release of the GEM object we hold the struct_mutex. As the
object may be holding onto the last reference for the task->mm,
calling mmput() may trigger exit_mmap() which close the vma
which will call drm_gem_vm_close() and attempt to reacquire
the struct_mutex. In order to avoid that recursion, we have
to defer the mmput() until after we drop the struct_mutex,
i.e. we need to schedule a worker to do the clean up. A further issue
spotted by Tvrtko was caused when we took a GTT mmapping of a userptr
buffer object. In that case, we would never call mmput as the object
would be cyclically referenced by the GTT mmapping and not freed upon
process exit - keeping the entire process mm alive after the process
task was reaped. The fix employed is to replace the mm_users/mmput()
reference handling to mm_count/mmdrop() for the shared i915_mm_struct.

   INFO: task test_surfaces:1632 blocked for more than 120 seconds.
         Tainted: GF          O 3.14.5+ #1
   "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
   test_surfaces   D 0000000000000000     0  1632   1590 0x00000082
    ffff88014914baa8 0000000000000046 0000000000000000 ffff88014914a010
    0000000000012c40 0000000000012c40 ffff8800a0058210 ffff88014784b010
    ffff88014914a010 ffff880037b1c820 ffff8800a0058210 ffff880037b1c824
   Call Trace:
    [<ffffffff81582499>] schedule+0x29/0x70
    [<ffffffff815825fe>] schedule_preempt_disabled+0xe/0x10
    [<ffffffff81583b93>] __mutex_lock_slowpath+0x183/0x220
    [<ffffffff81583c53>] mutex_lock+0x23/0x40
    [<ffffffffa005c2a3>] drm_gem_vm_close+0x33/0x70 [drm]
    [<ffffffff8115a483>] remove_vma+0x33/0x70
    [<ffffffff8115a5dc>] exit_mmap+0x11c/0x170
    [<ffffffff8104d6eb>] mmput+0x6b/0x100
    [<ffffffffa00f44b9>] i915_gem_userptr_release+0x89/0xc0 [i915]
    [<ffffffffa00e6706>] i915_gem_free_object+0x126/0x250 [i915]
    [<ffffffffa005c06a>] drm_gem_object_free+0x2a/0x40 [drm]
    [<ffffffffa005cc32>] drm_gem_object_handle_unreference_unlocked+0xe2/0x120 [drm]
    [<ffffffffa005ccd4>] drm_gem_object_release_handle+0x64/0x90 [drm]
    [<ffffffff8127ffeb>] idr_for_each+0xab/0x100
    [<ffffffffa005cc70>] ?  drm_gem_object_handle_unreference_unlocked+0x120/0x120 [drm]
    [<ffffffff81583c46>] ? mutex_lock+0x16/0x40
    [<ffffffffa005c354>] drm_gem_release+0x24/0x40 [drm]
    [<ffffffffa005b82b>] drm_release+0x3fb/0x480 [drm]
    [<ffffffff8118d482>] __fput+0xb2/0x260
    [<ffffffff8118d6de>] ____fput+0xe/0x10
    [<ffffffff8106f27f>] task_work_run+0x8f/0xf0
    [<ffffffff81052228>] do_exit+0x1a8/0x480
    [<ffffffff81052551>] do_group_exit+0x51/0xc0
    [<ffffffff810525d7>] SyS_exit_group+0x17/0x20
    [<ffffffff8158e092>] system_call_fastpath+0x16/0x1b

v2: Incorporate feedback from Tvrtko and remove the unnessary mm
referencing when creating the i915_mm_struct and improve some of the
function names and comments.

Reported-by: Jacek Danecki <jacek.danecki@intel.com>
Test-case: igt/gem_userptr_blits/process-exit*
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Tested-by: "Gong, Zhipeng" <zhipeng.gong@intel.com>
Cc: Jacek Danecki <jacek.danecki@intel.com>
Cc: "Ursulin, Tvrtko" <tvrtko.ursulin@intel.com>
Reviewed-by: "Ursulin, Tvrtko" <tvrtko.ursulin@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: stable@vger.kernel.org # hold off until 3.17 ships for additional testing
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
This commit is contained in:
Chris Wilson 2014-08-07 14:20:40 +01:00 committed by Jani Nikula
parent 2ce7598c9a
commit ad46cb533d
2 changed files with 235 additions and 184 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
drivers/gpu/drm/i915/i915_drv.h
View File

@ -184,6 +184,7 @@ enum hpd_pin {
if ((1 << (domain)) & (mask))
struct drm_i915_private;
struct i915_mm_struct;
struct i915_mmu_object;
enum intel_dpll_id {
@ -1506,9 +1507,8 @@ struct drm_i915_private {
struct i915_gtt gtt; /* VM representing the global address space */
struct i915_gem_mm mm;
#if defined(CONFIG_MMU_NOTIFIER)
DECLARE_HASHTABLE(mmu_notifiers, 7);
#endif
DECLARE_HASHTABLE(mm_structs, 7);
struct mutex mm_lock;
/* Kernel Modesetting */
@ -1814,8 +1814,8 @@ struct drm_i915_gem_object {
unsigned workers :4;
#define I915_GEM_USERPTR_MAX_WORKERS 15
struct mm_struct *mm;
struct i915_mmu_object *mn;
struct i915_mm_struct *mm;
struct i915_mmu_object *mmu_object;
struct work_struct *work;
} userptr;
};

407
drivers/gpu/drm/i915/i915_gem_userptr.c
View File

@ -32,6 +32,15 @@
#include <linux/mempolicy.h>
#include <linux/swap.h>
struct i915_mm_struct {
struct mm_struct *mm;
struct drm_device *dev;
struct i915_mmu_notifier *mn;
struct hlist_node node;
struct kref kref;
struct work_struct work;
};
#if defined(CONFIG_MMU_NOTIFIER)
#include <linux/interval_tree.h>
@ -41,16 +50,12 @@ struct i915_mmu_notifier {
struct mmu_notifier mn;
struct rb_root objects;
struct list_head linear;
struct drm_device *dev;
struct mm_struct *mm;
struct work_struct work;
unsigned long count;
unsigned long serial;
bool has_linear;
};
struct i915_mmu_object {
struct i915_mmu_notifier *mmu;
struct i915_mmu_notifier *mn;
struct interval_tree_node it;
struct list_head link;
struct drm_i915_gem_object *obj;
@ -96,18 +101,18 @@ static void *invalidate_range__linear(struct i915_mmu_notifier *mn,
unsigned long start,
unsigned long end)
{
struct i915_mmu_object *mmu;
struct i915_mmu_object *mo;
unsigned long serial;
restart:
serial = mn->serial;
list_for_each_entry(mmu, &mn->linear, link) {
list_for_each_entry(mo, &mn->linear, link) {
struct drm_i915_gem_object *obj;
if (mmu->it.last < start || mmu->it.start > end)
if (mo->it.last < start || mo->it.start > end)
continue;
obj = mmu->obj;
obj = mo->obj;
drm_gem_object_reference(&obj->base);
spin_unlock(&mn->lock);
@ -160,130 +165,47 @@ static const struct mmu_notifier_ops i915_gem_userptr_notifier = {
};
static struct i915_mmu_notifier *
__i915_mmu_notifier_lookup(struct drm_device *dev, struct mm_struct *mm)
i915_mmu_notifier_create(struct mm_struct *mm)
{
struct drm_i915_private *dev_priv = to_i915(dev);
struct i915_mmu_notifier *mmu;
/* Protected by dev->struct_mutex */
hash_for_each_possible(dev_priv->mmu_notifiers, mmu, node, (unsigned long)mm)
if (mmu->mm == mm)
return mmu;
return NULL;
}
static struct i915_mmu_notifier *
i915_mmu_notifier_get(struct drm_device *dev, struct mm_struct *mm)
{
struct drm_i915_private *dev_priv = to_i915(dev);
struct i915_mmu_notifier *mmu;
struct i915_mmu_notifier *mn;
int ret;
lockdep_assert_held(&dev->struct_mutex);
mmu = __i915_mmu_notifier_lookup(dev, mm);
if (mmu)
return mmu;
mmu = kmalloc(sizeof(*mmu), GFP_KERNEL);
if (mmu == NULL)
mn = kmalloc(sizeof(*mn), GFP_KERNEL);
if (mn == NULL)
return ERR_PTR(-ENOMEM);
spin_lock_init(&mmu->lock);
mmu->dev = dev;
mmu->mn.ops = &i915_gem_userptr_notifier;
mmu->mm = mm;
mmu->objects = RB_ROOT;
mmu->count = 0;
mmu->serial = 1;
INIT_LIST_HEAD(&mmu->linear);
mmu->has_linear = false;
spin_lock_init(&mn->lock);
mn->mn.ops = &i915_gem_userptr_notifier;
mn->objects = RB_ROOT;
mn->serial = 1;
INIT_LIST_HEAD(&mn->linear);
mn->has_linear = false;
/* Protected by mmap_sem (write-lock) */
ret = __mmu_notifier_register(&mmu->mn, mm);
ret = __mmu_notifier_register(&mn->mn, mm);
if (ret) {
kfree(mmu);
kfree(mn);
return ERR_PTR(ret);
}
/* Protected by dev->struct_mutex */
hash_add(dev_priv->mmu_notifiers, &mmu->node, (unsigned long)mm);
return mmu;
return mn;
}
static void
__i915_mmu_notifier_destroy_worker(struct work_struct *work)
static void __i915_mmu_notifier_update_serial(struct i915_mmu_notifier *mn)
{
struct i915_mmu_notifier *mmu = container_of(work, typeof(*mmu), work);
mmu_notifier_unregister(&mmu->mn, mmu->mm);
kfree(mmu);
}
static void
__i915_mmu_notifier_destroy(struct i915_mmu_notifier *mmu)
{
lockdep_assert_held(&mmu->dev->struct_mutex);
/* Protected by dev->struct_mutex */
hash_del(&mmu->node);
/* Our lock ordering is: mmap_sem, mmu_notifier_scru, struct_mutex.
* We enter the function holding struct_mutex, therefore we need
* to drop our mutex prior to calling mmu_notifier_unregister in
* order to prevent lock inversion (and system-wide deadlock)
* between the mmap_sem and struct-mutex. Hence we defer the
* unregistration to a workqueue where we hold no locks.
*/
INIT_WORK(&mmu->work, __i915_mmu_notifier_destroy_worker);
schedule_work(&mmu->work);
}
static void __i915_mmu_notifier_update_serial(struct i915_mmu_notifier *mmu)
{
if (++mmu->serial == 0)
mmu->serial = 1;
}
static bool i915_mmu_notifier_has_linear(struct i915_mmu_notifier *mmu)
{
struct i915_mmu_object *mn;
list_for_each_entry(mn, &mmu->linear, link)
if (mn->is_linear)
return true;
return false;
}
static void
i915_mmu_notifier_del(struct i915_mmu_notifier *mmu,
struct i915_mmu_object *mn)
{
lockdep_assert_held(&mmu->dev->struct_mutex);
spin_lock(&mmu->lock);
list_del(&mn->link);
if (mn->is_linear)
mmu->has_linear = i915_mmu_notifier_has_linear(mmu);
else
interval_tree_remove(&mn->it, &mmu->objects);
__i915_mmu_notifier_update_serial(mmu);
spin_unlock(&mmu->lock);
/* Protected against _add() by dev->struct_mutex */
if (--mmu->count == 0)
__i915_mmu_notifier_destroy(mmu);
if (++mn->serial == 0)
mn->serial = 1;
}
static int
i915_mmu_notifier_add(struct i915_mmu_notifier *mmu,
struct i915_mmu_object *mn)
i915_mmu_notifier_add(struct drm_device *dev,
struct i915_mmu_notifier *mn,
struct i915_mmu_object *mo)
{
struct interval_tree_node *it;
int ret;
ret = i915_mutex_lock_interruptible(mmu->dev);
ret = i915_mutex_lock_interruptible(dev);
if (ret)
return ret;
@ -291,11 +213,11 @@ i915_mmu_notifier_add(struct i915_mmu_notifier *mmu,
* remove the objects from the interval tree) before we do
* the check for overlapping objects.
*/
i915_gem_retire_requests(mmu->dev);
i915_gem_retire_requests(dev);
spin_lock(&mmu->lock);
it = interval_tree_iter_first(&mmu->objects,
mn->it.start, mn->it.last);
spin_lock(&mn->lock);
it = interval_tree_iter_first(&mn->objects,
mo->it.start, mo->it.last);
if (it) {
struct drm_i915_gem_object *obj;
@ -312,86 +234,122 @@ i915_mmu_notifier_add(struct i915_mmu_notifier *mmu,
obj = container_of(it, struct i915_mmu_object, it)->obj;
if (!obj->userptr.workers)
mmu->has_linear = mn->is_linear = true;
mn->has_linear = mo->is_linear = true;
else
ret = -EAGAIN;
} else
interval_tree_insert(&mn->it, &mmu->objects);
interval_tree_insert(&mo->it, &mn->objects);
if (ret == 0) {
list_add(&mn->link, &mmu->linear);
__i915_mmu_notifier_update_serial(mmu);
list_add(&mo->link, &mn->linear);
__i915_mmu_notifier_update_serial(mn);
}
spin_unlock(&mmu->lock);
mutex_unlock(&mmu->dev->struct_mutex);
spin_unlock(&mn->lock);
mutex_unlock(&dev->struct_mutex);
return ret;
}
static bool i915_mmu_notifier_has_linear(struct i915_mmu_notifier *mn)
{
struct i915_mmu_object *mo;
list_for_each_entry(mo, &mn->linear, link)
if (mo->is_linear)
return true;
return false;
}
static void
i915_mmu_notifier_del(struct i915_mmu_notifier *mn,
struct i915_mmu_object *mo)
{
spin_lock(&mn->lock);
list_del(&mo->link);
if (mo->is_linear)
mn->has_linear = i915_mmu_notifier_has_linear(mn);
else
interval_tree_remove(&mo->it, &mn->objects);
__i915_mmu_notifier_update_serial(mn);
spin_unlock(&mn->lock);
}
static void
i915_gem_userptr_release__mmu_notifier(struct drm_i915_gem_object *obj)
{
struct i915_mmu_object *mn;
struct i915_mmu_object *mo;
mn = obj->userptr.mn;
if (mn == NULL)
mo = obj->userptr.mmu_object;
if (mo == NULL)
return;
i915_mmu_notifier_del(mn->mmu, mn);
obj->userptr.mn = NULL;
i915_mmu_notifier_del(mo->mn, mo);
kfree(mo);
obj->userptr.mmu_object = NULL;
}
static struct i915_mmu_notifier *
i915_mmu_notifier_find(struct i915_mm_struct *mm)
{
if (mm->mn == NULL) {
down_write(&mm->mm->mmap_sem);
mutex_lock(&to_i915(mm->dev)->mm_lock);
if (mm->mn == NULL)
mm->mn = i915_mmu_notifier_create(mm->mm);
mutex_unlock(&to_i915(mm->dev)->mm_lock);
up_write(&mm->mm->mmap_sem);
}
return mm->mn;
}
static int
i915_gem_userptr_init__mmu_notifier(struct drm_i915_gem_object *obj,
unsigned flags)
{
struct i915_mmu_notifier *mmu;
struct i915_mmu_object *mn;
struct i915_mmu_notifier *mn;
struct i915_mmu_object *mo;
int ret;
if (flags & I915_USERPTR_UNSYNCHRONIZED)
return capable(CAP_SYS_ADMIN) ? 0 : -EPERM;
down_write(&obj->userptr.mm->mmap_sem);
ret = i915_mutex_lock_interruptible(obj->base.dev);
if (ret == 0) {
mmu = i915_mmu_notifier_get(obj->base.dev, obj->userptr.mm);
if (!IS_ERR(mmu))
mmu->count++; /* preemptive add to act as a refcount */
else
ret = PTR_ERR(mmu);
mutex_unlock(&obj->base.dev->struct_mutex);
}
up_write(&obj->userptr.mm->mmap_sem);
if (ret)
if (WARN_ON(obj->userptr.mm == NULL))
return -EINVAL;
mn = i915_mmu_notifier_find(obj->userptr.mm);
if (IS_ERR(mn))
return PTR_ERR(mn);
mo = kzalloc(sizeof(*mo), GFP_KERNEL);
if (mo == NULL)
return -ENOMEM;
mo->mn = mn;
mo->it.start = obj->userptr.ptr;
mo->it.last = mo->it.start + obj->base.size - 1;
mo->obj = obj;
ret = i915_mmu_notifier_add(obj->base.dev, mn, mo);
if (ret) {
kfree(mo);
return ret;
mn = kzalloc(sizeof(*mn), GFP_KERNEL);
if (mn == NULL) {
ret = -ENOMEM;
goto destroy_mmu;
}
mn->mmu = mmu;
mn->it.start = obj->userptr.ptr;
mn->it.last = mn->it.start + obj->base.size - 1;
mn->obj = obj;
ret = i915_mmu_notifier_add(mmu, mn);
if (ret)
goto free_mn;
obj->userptr.mn = mn;
obj->userptr.mmu_object = mo;
return 0;
}
free_mn:
static void
i915_mmu_notifier_free(struct i915_mmu_notifier *mn,
struct mm_struct *mm)
{
if (mn == NULL)
return;
mmu_notifier_unregister(&mn->mn, mm);
kfree(mn);
destroy_mmu:
mutex_lock(&obj->base.dev->struct_mutex);
if (--mmu->count == 0)
__i915_mmu_notifier_destroy(mmu);
mutex_unlock(&obj->base.dev->struct_mutex);
return ret;
}
#else
@ -413,15 +371,114 @@ i915_gem_userptr_init__mmu_notifier(struct drm_i915_gem_object *obj,
return 0;
}
static void
i915_mmu_notifier_free(struct i915_mmu_notifier *mn,
struct mm_struct *mm)
{
}
#endif
static struct i915_mm_struct *
__i915_mm_struct_find(struct drm_i915_private *dev_priv, struct mm_struct *real)
{
struct i915_mm_struct *mm;
/* Protected by dev_priv->mm_lock */
hash_for_each_possible(dev_priv->mm_structs, mm, node, (unsigned long)real)
if (mm->mm == real)
return mm;
return NULL;
}
static int
i915_gem_userptr_init__mm_struct(struct drm_i915_gem_object *obj)
{
struct drm_i915_private *dev_priv = to_i915(obj->base.dev);
struct i915_mm_struct *mm;
int ret = 0;
/* During release of the GEM object we hold the struct_mutex. This
* precludes us from calling mmput() at that time as that may be
* the last reference and so call exit_mmap(). exit_mmap() will
* attempt to reap the vma, and if we were holding a GTT mmap
* would then call drm_gem_vm_close() and attempt to reacquire
* the struct mutex. So in order to avoid that recursion, we have
* to defer releasing the mm reference until after we drop the
* struct_mutex, i.e. we need to schedule a worker to do the clean
* up.
*/
mutex_lock(&dev_priv->mm_lock);
mm = __i915_mm_struct_find(dev_priv, current->mm);
if (mm == NULL) {
mm = kmalloc(sizeof(*mm), GFP_KERNEL);
if (mm == NULL) {
ret = -ENOMEM;
goto out;
}
kref_init(&mm->kref);
mm->dev = obj->base.dev;
mm->mm = current->mm;
atomic_inc(&current->mm->mm_count);
mm->mn = NULL;
/* Protected by dev_priv->mm_lock */
hash_add(dev_priv->mm_structs,
&mm->node, (unsigned long)mm->mm);
} else
kref_get(&mm->kref);
obj->userptr.mm = mm;
out:
mutex_unlock(&dev_priv->mm_lock);
return ret;
}
static void
__i915_mm_struct_free__worker(struct work_struct *work)
{
struct i915_mm_struct *mm = container_of(work, typeof(*mm), work);
i915_mmu_notifier_free(mm->mn, mm->mm);
mmdrop(mm->mm);
kfree(mm);
}
static void
__i915_mm_struct_free(struct kref *kref)
{
struct i915_mm_struct *mm = container_of(kref, typeof(*mm), kref);
/* Protected by dev_priv->mm_lock */
hash_del(&mm->node);
mutex_unlock(&to_i915(mm->dev)->mm_lock);
INIT_WORK(&mm->work, __i915_mm_struct_free__worker);
schedule_work(&mm->work);
}
static void
i915_gem_userptr_release__mm_struct(struct drm_i915_gem_object *obj)
{
if (obj->userptr.mm == NULL)
return;
kref_put_mutex(&obj->userptr.mm->kref,
__i915_mm_struct_free,
&to_i915(obj->base.dev)->mm_lock);
obj->userptr.mm = NULL;
}
struct get_pages_work {
struct work_struct work;
struct drm_i915_gem_object *obj;
struct task_struct *task;
};
#if IS_ENABLED(CONFIG_SWIOTLB)
#define swiotlb_active() swiotlb_nr_tbl()
#else
@ -479,7 +536,7 @@ __i915_gem_userptr_get_pages_worker(struct work_struct *_work)
if (pvec == NULL)
pvec = drm_malloc_ab(num_pages, sizeof(struct page *));
if (pvec != NULL) {
struct mm_struct *mm = obj->userptr.mm;
struct mm_struct *mm = obj->userptr.mm->mm;
down_read(&mm->mmap_sem);
while (pinned < num_pages) {
@ -545,7 +602,7 @@ i915_gem_userptr_get_pages(struct drm_i915_gem_object *obj)
pvec = NULL;
pinned = 0;
if (obj->userptr.mm == current->mm) {
if (obj->userptr.mm->mm == current->mm) {
pvec = kmalloc(num_pages*sizeof(struct page *),
GFP_TEMPORARY | __GFP_NOWARN | __GFP_NORETRY);
if (pvec == NULL) {
@ -651,17 +708,13 @@ static void
i915_gem_userptr_release(struct drm_i915_gem_object *obj)
{
i915_gem_userptr_release__mmu_notifier(obj);
if (obj->userptr.mm) {
mmput(obj->userptr.mm);
obj->userptr.mm = NULL;
}
i915_gem_userptr_release__mm_struct(obj);
}
static int
i915_gem_userptr_dmabuf_export(struct drm_i915_gem_object *obj)
{
if (obj->userptr.mn)
if (obj->userptr.mmu_object)
return 0;
return i915_gem_userptr_init__mmu_notifier(obj, 0);
@ -736,7 +789,6 @@ i915_gem_userptr_ioctl(struct drm_device *dev, void *data, struct drm_file *file
return -ENODEV;
}
/* Allocate the new object */
obj = i915_gem_object_alloc(dev);
if (obj == NULL)
return -ENOMEM;
@ -754,8 +806,8 @@ i915_gem_userptr_ioctl(struct drm_device *dev, void *data, struct drm_file *file
* at binding. This means that we need to hook into the mmu_notifier
* in order to detect if the mmu is destroyed.
*/
ret = -ENOMEM;
if ((obj->userptr.mm = get_task_mm(current)))
ret = i915_gem_userptr_init__mm_struct(obj);
if (ret == 0)
ret = i915_gem_userptr_init__mmu_notifier(obj, args->flags);
if (ret == 0)
ret = drm_gem_handle_create(file, &obj->base, &handle);
@ -772,9 +824,8 @@ i915_gem_userptr_ioctl(struct drm_device *dev, void *data, struct drm_file *file
int
i915_gem_init_userptr(struct drm_device *dev)
{
#if defined(CONFIG_MMU_NOTIFIER)
struct drm_i915_private *dev_priv = to_i915(dev);
hash_init(dev_priv->mmu_notifiers);
#endif
mutex_init(&dev_priv->mm_lock);
hash_init(dev_priv->mm_structs);
return 0;
}