linux/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
Boris Brezillon 7d2d6d0129 drm/panfrost: Fix a deadlock between the shrinker and madvise path
panfrost_ioctl_madvise() and panfrost_gem_purge() acquire the mappings
and shmem locks in different orders, thus leading to a potential
the mappings lock first.

Fixes: bdefca2d8d ("drm/panfrost: Add the panfrost_gem_mapping concept")
Cc: <stable@vger.kernel.org>
Cc: Christian Hewitt <christianshewitt@gmail.com>
Reported-by: Christian Hewitt <christianshewitt@gmail.com>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201101174016.839110-1-boris.brezillon@collabora.com
2020-11-03 09:21:52 +01:00

123 lines
3.0 KiB
C

/* SPDX-License-Identifier: GPL-2.0 */
/* Copyright (C) 2019 Arm Ltd.
*
* Based on msm_gem_freedreno.c:
* Copyright (C) 2016 Red Hat
* Author: Rob Clark <robdclark@gmail.com>
*/
#include <linux/list.h>
#include <drm/drm_device.h>
#include <drm/drm_gem_shmem_helper.h>
#include "panfrost_device.h"
#include "panfrost_gem.h"
#include "panfrost_mmu.h"
static unsigned long
panfrost_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc)
{
struct panfrost_device *pfdev =
container_of(shrinker, struct panfrost_device, shrinker);
struct drm_gem_shmem_object *shmem;
unsigned long count = 0;
if (!mutex_trylock(&pfdev->shrinker_lock))
return 0;
list_for_each_entry(shmem, &pfdev->shrinker_list, madv_list) {
if (drm_gem_shmem_is_purgeable(shmem))
count += shmem->base.size >> PAGE_SHIFT;
}
mutex_unlock(&pfdev->shrinker_lock);
return count;
}
static bool panfrost_gem_purge(struct drm_gem_object *obj)
{
struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
struct panfrost_gem_object *bo = to_panfrost_bo(obj);
bool ret = false;
if (atomic_read(&bo->gpu_usecount))
return false;
if (!mutex_trylock(&bo->mappings.lock))
return false;
if (!mutex_trylock(&shmem->pages_lock))
goto unlock_mappings;
panfrost_gem_teardown_mappings_locked(bo);
drm_gem_shmem_purge_locked(obj);
ret = true;
mutex_unlock(&shmem->pages_lock);
unlock_mappings:
mutex_unlock(&bo->mappings.lock);
return ret;
}
static unsigned long
panfrost_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc)
{
struct panfrost_device *pfdev =
container_of(shrinker, struct panfrost_device, shrinker);
struct drm_gem_shmem_object *shmem, *tmp;
unsigned long freed = 0;
if (!mutex_trylock(&pfdev->shrinker_lock))
return SHRINK_STOP;
list_for_each_entry_safe(shmem, tmp, &pfdev->shrinker_list, madv_list) {
if (freed >= sc->nr_to_scan)
break;
if (drm_gem_shmem_is_purgeable(shmem) &&
panfrost_gem_purge(&shmem->base)) {
freed += shmem->base.size >> PAGE_SHIFT;
list_del_init(&shmem->madv_list);
}
}
mutex_unlock(&pfdev->shrinker_lock);
if (freed > 0)
pr_info_ratelimited("Purging %lu bytes\n", freed << PAGE_SHIFT);
return freed;
}
/**
* panfrost_gem_shrinker_init - Initialize panfrost shrinker
* @dev: DRM device
*
* This function registers and sets up the panfrost shrinker.
*/
void panfrost_gem_shrinker_init(struct drm_device *dev)
{
struct panfrost_device *pfdev = dev->dev_private;
pfdev->shrinker.count_objects = panfrost_gem_shrinker_count;
pfdev->shrinker.scan_objects = panfrost_gem_shrinker_scan;
pfdev->shrinker.seeks = DEFAULT_SEEKS;
WARN_ON(register_shrinker(&pfdev->shrinker));
}
/**
* panfrost_gem_shrinker_cleanup - Clean up panfrost shrinker
* @dev: DRM device
*
* This function unregisters the panfrost shrinker.
*/
void panfrost_gem_shrinker_cleanup(struct drm_device *dev)
{
struct panfrost_device *pfdev = dev->dev_private;
if (pfdev->shrinker.nr_deferred) {
unregister_shrinker(&pfdev->shrinker);
}
}