| Message ID | 20190823021216.5862-6-robh@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2,1/8] drm/panfrost: Fix possible suspend in panfrost_remove | expand |
On 23/08/2019 03:12, Rob Herring wrote: > Lockdep reports a circular locking dependency with pages_lock taken in > the shrinker callback. The deadlock can't actually happen with current > users at least as a BO will never be purgeable when pages_lock is held. > To be safe, let's use mutex_trylock() instead and bail if a BO is locked > already. > > WARNING: possible circular locking dependency detected > 5.3.0-rc1+ #100 Tainted: G L > ------------------------------------------------------ > kswapd0/171 is trying to acquire lock: > 000000009b9823fd (&shmem->pages_lock){+.+.}, at: drm_gem_shmem_purge+0x20/0x40 > > but task is already holding lock: > 00000000f82369b6 (fs_reclaim){+.+.}, at: __fs_reclaim_acquire+0x0/0x40 > > which lock already depends on the new lock. > > the existing dependency chain (in reverse order) is: > > -> #1 (fs_reclaim){+.+.}: > fs_reclaim_acquire.part.18+0x34/0x40 > fs_reclaim_acquire+0x20/0x28 > __kmalloc_node+0x6c/0x4c0 > kvmalloc_node+0x38/0xa8 > drm_gem_get_pages+0x80/0x1d0 > drm_gem_shmem_get_pages+0x58/0xa0 > drm_gem_shmem_get_pages_sgt+0x48/0xd0 > panfrost_mmu_map+0x38/0xf8 [panfrost] > panfrost_gem_open+0xc0/0xe8 [panfrost] > drm_gem_handle_create_tail+0xe8/0x198 > drm_gem_handle_create+0x3c/0x50 > panfrost_gem_create_with_handle+0x70/0xa0 [panfrost] > panfrost_ioctl_create_bo+0x48/0x80 [panfrost] > drm_ioctl_kernel+0xb8/0x110 > drm_ioctl+0x244/0x3f0 > do_vfs_ioctl+0xbc/0x910 > ksys_ioctl+0x78/0xa8 > __arm64_sys_ioctl+0x1c/0x28 > el0_svc_common.constprop.0+0x90/0x168 > el0_svc_handler+0x28/0x78 > el0_svc+0x8/0xc > > -> #0 (&shmem->pages_lock){+.+.}: > __lock_acquire+0xa2c/0x1d70 > lock_acquire+0xdc/0x228 > __mutex_lock+0x8c/0x800 > mutex_lock_nested+0x1c/0x28 > drm_gem_shmem_purge+0x20/0x40 > panfrost_gem_shrinker_scan+0xc0/0x180 [panfrost] > do_shrink_slab+0x208/0x500 > shrink_slab+0x10c/0x2c0 > shrink_node+0x28c/0x4d8 > balance_pgdat+0x2c8/0x570 > kswapd+0x22c/0x638 > kthread+0x128/0x130 > ret_from_fork+0x10/0x18 > > other info that might help us debug this: > > Possible unsafe locking scenario: > > CPU0 CPU1 > ---- ---- > lock(fs_reclaim); > lock(&shmem->pages_lock); > lock(fs_reclaim); > lock(&shmem->pages_lock); > > *** DEADLOCK *** > > 3 locks held by kswapd0/171: > #0: 00000000f82369b6 (fs_reclaim){+.+.}, at: __fs_reclaim_acquire+0x0/0x40 > #1: 00000000ceb37808 (shrinker_rwsem){++++}, at: shrink_slab+0xbc/0x2c0 > #2: 00000000f31efa81 (&pfdev->shrinker_lock){+.+.}, at: panfrost_gem_shrinker_scan+0x34/0x180 [panfrost] > > Fixes: 17acb9f35ed7 ("drm/shmem: Add madvise state and purge helpers") > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> > Cc: Maxime Ripard <maxime.ripard@bootlin.com> > Cc: Sean Paul <sean@poorly.run> > Cc: David Airlie <airlied@linux.ie> > Cc: Daniel Vetter <daniel@ffwll.ch> > Signed-off-by: Rob Herring <robh@kernel.org> I thought I'd already given my R-b for this one, but just in case: Reviewed-by: Steven Price <steven.price@arm.com> Steve > --- > drivers/gpu/drm/drm_gem_shmem_helper.c | 7 +++++-- > include/drm/drm_gem_shmem_helper.h | 2 +- > 2 files changed, 6 insertions(+), 3 deletions(-) > > diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c > index 5423ec56b535..f5918707672f 100644 > --- a/drivers/gpu/drm/drm_gem_shmem_helper.c > +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c > @@ -415,13 +415,16 @@ void drm_gem_shmem_purge_locked(struct drm_gem_object *obj) > } > EXPORT_SYMBOL(drm_gem_shmem_purge_locked); > > -void drm_gem_shmem_purge(struct drm_gem_object *obj) > +bool drm_gem_shmem_purge(struct drm_gem_object *obj) > { > struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj); > > - mutex_lock(&shmem->pages_lock); > + if (!mutex_trylock(&shmem->pages_lock)) > + return false; > drm_gem_shmem_purge_locked(obj); > mutex_unlock(&shmem->pages_lock); > + > + return true; > } > EXPORT_SYMBOL(drm_gem_shmem_purge); > > diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h > index ce1600fdfc3e..01f514521687 100644 > --- a/include/drm/drm_gem_shmem_helper.h > +++ b/include/drm/drm_gem_shmem_helper.h > @@ -134,7 +134,7 @@ static inline bool drm_gem_shmem_is_purgeable(struct drm_gem_shmem_object *shmem > } > > void drm_gem_shmem_purge_locked(struct drm_gem_object *obj); > -void drm_gem_shmem_purge(struct drm_gem_object *obj); > +bool drm_gem_shmem_purge(struct drm_gem_object *obj); > > struct drm_gem_shmem_object * > drm_gem_shmem_create_with_handle(struct drm_file *file_priv, >
diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c index 5423ec56b535..f5918707672f 100644 --- a/drivers/gpu/drm/drm_gem_shmem_helper.c +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c @@ -415,13 +415,16 @@ void drm_gem_shmem_purge_locked(struct drm_gem_object *obj) } EXPORT_SYMBOL(drm_gem_shmem_purge_locked); -void drm_gem_shmem_purge(struct drm_gem_object *obj) +bool drm_gem_shmem_purge(struct drm_gem_object *obj) { struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj); - mutex_lock(&shmem->pages_lock); + if (!mutex_trylock(&shmem->pages_lock)) + return false; drm_gem_shmem_purge_locked(obj); mutex_unlock(&shmem->pages_lock); + + return true; } EXPORT_SYMBOL(drm_gem_shmem_purge); diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h index ce1600fdfc3e..01f514521687 100644 --- a/include/drm/drm_gem_shmem_helper.h +++ b/include/drm/drm_gem_shmem_helper.h @@ -134,7 +134,7 @@ static inline bool drm_gem_shmem_is_purgeable(struct drm_gem_shmem_object *shmem } void drm_gem_shmem_purge_locked(struct drm_gem_object *obj); -void drm_gem_shmem_purge(struct drm_gem_object *obj); +bool drm_gem_shmem_purge(struct drm_gem_object *obj); struct drm_gem_shmem_object * drm_gem_shmem_create_with_handle(struct drm_file *file_priv,
Lockdep reports a circular locking dependency with pages_lock taken in the shrinker callback. The deadlock can't actually happen with current users at least as a BO will never be purgeable when pages_lock is held. To be safe, let's use mutex_trylock() instead and bail if a BO is locked already. WARNING: possible circular locking dependency detected 5.3.0-rc1+ #100 Tainted: G L ------------------------------------------------------ kswapd0/171 is trying to acquire lock: 000000009b9823fd (&shmem->pages_lock){+.+.}, at: drm_gem_shmem_purge+0x20/0x40 but task is already holding lock: 00000000f82369b6 (fs_reclaim){+.+.}, at: __fs_reclaim_acquire+0x0/0x40 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (fs_reclaim){+.+.}: fs_reclaim_acquire.part.18+0x34/0x40 fs_reclaim_acquire+0x20/0x28 __kmalloc_node+0x6c/0x4c0 kvmalloc_node+0x38/0xa8 drm_gem_get_pages+0x80/0x1d0 drm_gem_shmem_get_pages+0x58/0xa0 drm_gem_shmem_get_pages_sgt+0x48/0xd0 panfrost_mmu_map+0x38/0xf8 [panfrost] panfrost_gem_open+0xc0/0xe8 [panfrost] drm_gem_handle_create_tail+0xe8/0x198 drm_gem_handle_create+0x3c/0x50 panfrost_gem_create_with_handle+0x70/0xa0 [panfrost] panfrost_ioctl_create_bo+0x48/0x80 [panfrost] drm_ioctl_kernel+0xb8/0x110 drm_ioctl+0x244/0x3f0 do_vfs_ioctl+0xbc/0x910 ksys_ioctl+0x78/0xa8 __arm64_sys_ioctl+0x1c/0x28 el0_svc_common.constprop.0+0x90/0x168 el0_svc_handler+0x28/0x78 el0_svc+0x8/0xc -> #0 (&shmem->pages_lock){+.+.}: __lock_acquire+0xa2c/0x1d70 lock_acquire+0xdc/0x228 __mutex_lock+0x8c/0x800 mutex_lock_nested+0x1c/0x28 drm_gem_shmem_purge+0x20/0x40 panfrost_gem_shrinker_scan+0xc0/0x180 [panfrost] do_shrink_slab+0x208/0x500 shrink_slab+0x10c/0x2c0 shrink_node+0x28c/0x4d8 balance_pgdat+0x2c8/0x570 kswapd+0x22c/0x638 kthread+0x128/0x130 ret_from_fork+0x10/0x18 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(fs_reclaim); lock(&shmem->pages_lock); lock(fs_reclaim); lock(&shmem->pages_lock); *** DEADLOCK *** 3 locks held by kswapd0/171: #0: 00000000f82369b6 (fs_reclaim){+.+.}, at: __fs_reclaim_acquire+0x0/0x40 #1: 00000000ceb37808 (shrinker_rwsem){++++}, at: shrink_slab+0xbc/0x2c0 #2: 00000000f31efa81 (&pfdev->shrinker_lock){+.+.}, at: panfrost_gem_shrinker_scan+0x34/0x180 [panfrost] Fixes: 17acb9f35ed7 ("drm/shmem: Add madvise state and purge helpers") Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Maxime Ripard <maxime.ripard@bootlin.com> Cc: Sean Paul <sean@poorly.run> Cc: David Airlie <airlied@linux.ie> Cc: Daniel Vetter <daniel@ffwll.ch> Signed-off-by: Rob Herring <robh@kernel.org> --- drivers/gpu/drm/drm_gem_shmem_helper.c | 7 +++++-- include/drm/drm_gem_shmem_helper.h | 2 +- 2 files changed, 6 insertions(+), 3 deletions(-)