Hi Daniel,
On 2017-12-13 11:45, Daniel Vetter wrote:
PROBE_DEFER also uses system_wq to reprobe drivers, which means when
that again fails, and we try to flush the overall system_wq (to get
all the delayed connectore cleanup work_struct completed), we
deadlock.
Fix this by using just a single cleanup work, so that we can only
flush that one and don't block on anything else. That means a free
list plus locking, a standard pattern.
Fixes: a703c55004e1 ("drm: safely free connectors from connector_iter")
Fixes: 613051dac40d ("drm: locking&new iterators for connector_list")
Cc: Ben Widawsky <ben@xxxxxxxxxxxx>
Cc: Dave Airlie <airlied@xxxxxxxxx>
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Sean Paul <seanpaul@xxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # v4.11+: 613051dac40d ("drm: locking&new iterators for connector_list"
Cc: <stable@xxxxxxxxxxxxxxx> # v4.11+
Cc: Daniel Vetter <daniel.vetter@xxxxxxxxx>
Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>
Cc: Gustavo Padovan <gustavo@xxxxxxxxxxx>
Cc: David Airlie <airlied@xxxxxxxx>
Cc: Javier Martinez Canillas <javier@xxxxxxxxxxxx>
Cc: Shuah Khan <shuahkh@xxxxxxxxxxxxxxx>
Cc: Guillaume Tucker <guillaume.tucker@xxxxxxxxxxxxx>
Cc: Mark Brown <broonie@xxxxxxxxxx>
Cc: Kevin Hilman <khilman@xxxxxxxxxxxx>
Cc: Matt Hart <matthew.hart@xxxxxxxxxx>
Cc: Thierry Escande <thierry.escande@xxxxxxxxxxxxxxx>
Cc: Tomeu Vizoso <tomeu.vizoso@xxxxxxxxxxxxx>
Cc: Enric Balletbo i Serra <enric.balletbo@xxxxxxxxxxxxx>
Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx>
Sadly, this patch doesn't work in my test environment (Samsung Snow
Chromebook with modified DTS), which reproduces the problem discussed
inhttps://www.spinics.net/lists/arm-kernel/msg622332.html
[ 4.925178] exynos-drm exynos-drm: failed to bind 14530000.hdmi (ops
hdmi_component_ops): -19
[ 4.936167] Unable to handle kernel paging request at virtual address
fffffcac
[ 4.942004] pgd = ad8213ad
[ 4.944654] [fffffcac] *pgd=6fffd861, *pte=00000000, *ppte=00000000
[ 4.950944] Internal error: Oops: 37 [#1] PREEMPT SMP ARM
[ 4.956284] Modules linked in:
[ 4.959324] CPU: 1 PID: 80 Comm: kworker/1:3 Not tainted
4.15.0-rc3-next-20171212-00004-g879e6206b6fb-dirty #56
[ 4.969391] Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
[ 4.975472] Workqueue: events drm_connector_free_work_fn
[ 4.980765] PC is at drm_mode_object_unregister+0x1c/0x48
[ 4.986146] LR is at __mutex_lock+0x3ec/0xa0c
[ 4.990483] pc : [<c050e744>] lr : [<c0a0465c>] psr: 60000113
[ 4.996731] sp : ed27dec0 ip : ed27c000 fp : ed25042c
[ 5.001940] r10: 00000000 r9 : c1008c6c r8 : c10ae6d4
[ 5.007148] r7 : ed2503ec r6 : ed250000 r5 : fffffcac r4 : ed250330
[ 5.013659] r3 : 00000000 r2 : 00000001 r1 : ed27de50 r0 : 00000000
[ 5.020170] Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM
Segment none
[ 5.027286] Control: 10c5387d Table: 4000406a DAC: 00000051
[ 5.033016] Process kworker/1:3 (pid: 80, stack limit = 0x37cd389f)
[ 5.039265] Stack: (0xed27dec0 to 0xed27e000)
[ 5.043607] dec0: fffffc98 ed27ded0 ed250000 c050d374 ed242f78
ed242f78 00000001 ed22e200
[ 5.051766] dee0: eefc91c0 eefcc500 c10ad21d c0143438 00000001
00000000 c0143384 c0143534
[ 5.059925] df00: 00000001 00000000 c0143384 00000000 edd0ce00
c181658c c1214a78 00000000
[ 5.068084] df20: c0d7c514 00000000 c120f048 ed22e200 ed22e218
eefc91f8 c0143ae8 c10ae166
[ 5.076243] df40: 00000008 ed22e218 c1005d00 c0143a2c eefcc5f5
ed22e200 eefc91c0 c0143c4c
[ 5.084402] df60: c0a09894 ed709100 00000000 ed709100 00000000
ed25e000 ed709180 ed22e200
[ 5.092561] df80: edfdfe68 c0143a3c 00000000 c014a1c4 ed25e000
c014a074 00000000 00000000
[ 5.100720] dfa0: 00000000 00000000 00000000 c01010b4 00000000
00000000 00000000 00000000
[ 5.108879] dfc0: 00000000 00000000 00000000 00000000 00000000
00000000 00000000 00000000
[ 5.117039] dfe0: 00000000 00000000 00000000 00000000 00000013
00000000 00000000 00000000
[ 5.125202] [<c050e744>] (drm_mode_object_unregister) from
[<c050d374>] (drm_connector_free_work_fn+0x80/0xa8)
[ 5.135185] [<c050d374>] (drm_connector_free_work_fn) from
[<c0143438>] (process_one_work+0x1dc/0x7a8)
[ 5.144472] [<c0143438>] (process_one_work) from [<c0143a2c>]
(process_scheduled_works+0x28/0x38)
[ 5.153324] [<c0143a2c>] (process_scheduled_works) from [<c0143c4c>]
(worker_thread+0x210/0x4dc)
[ 5.162092] [<c0143c4c>] (worker_thread) from [<c014a1c4>]
(kthread+0x150/0x19c)
[ 5.169469] [<c014a1c4>] (kthread) from [<c01010b4>]
(ret_from_fork+0x14/0x20)
[ 5.176669] Exception stack(0xed27dfb0 to 0xed27dff8)
[ 5.181704] dfa0: 00000000
00000000 00000000 00000000
[ 5.189864] dfc0: 00000000 00000000 00000000 00000000 00000000
00000000 00000000 00000000
[ 5.198023] dfe0: 00000000 00000000 00000000 00000000 00000013 00000000
[ 5.204622] Code: e1a06000 e3a01000 e1a00004 eb13d968 (e5951000)
[ 5.210731] ---[ end trace 55b8b9b30581db4f ]---
I will try to provide a bit more details soon.
---
drivers/gpu/drm/drm_connector.c | 46 ++++++++++++++++++++++++++-----------
drivers/gpu/drm/drm_crtc_internal.h | 1 +
drivers/gpu/drm/drm_mode_config.c | 5 +++-
include/drm/drm_connector.h | 4 ++--
include/drm/drm_mode_config.h | 17 +++++++++++++-
5 files changed, 55 insertions(+), 18 deletions(-)
diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
index 0b7e0974e6da..2f43dc217936 100644
--- a/drivers/gpu/drm/drm_connector.c
+++ b/drivers/gpu/drm/drm_connector.c
@@ -153,14 +153,23 @@ static void drm_connector_free(struct kref *kref)
connector->funcs->destroy(connector);
}
-static void drm_connector_free_work_fn(struct work_struct *work)
+void drm_connector_free_work_fn(struct work_struct *work)
{
- struct drm_connector *connector =
- container_of(work, struct drm_connector, free_work);
- struct drm_device *dev = connector->dev;
+ struct drm_connector *connector;
+ struct drm_device *dev =
+ container_of(work, struct drm_device, mode_config.connector_free_work);
+ struct drm_mode_config *config = &dev->mode_config;
+ unsigned long flags;
+ LIST_HEAD(list_head);
- drm_mode_object_unregister(dev, &connector->base);
- connector->funcs->destroy(connector);
+ spin_lock_irqsave(&config->connector_list_lock, flags);
+ list_splice(&config->connector_free_list, &list_head);
+ spin_unlock_irqrestore(&config->connector_list_lock, flags);
+
+ list_for_each_entry(connector, &list_head, free_head) {
+ drm_mode_object_unregister(dev, &connector->base);
+ connector->funcs->destroy(connector);
+ }
}
/**
@@ -192,8 +201,6 @@ int drm_connector_init(struct drm_device *dev,
if (ret)
return ret;
- INIT_WORK(&connector->free_work, drm_connector_free_work_fn);
-
connector->base.properties = &connector->properties;
connector->dev = dev;
connector->funcs = funcs;
@@ -550,10 +557,15 @@ EXPORT_SYMBOL(drm_connector_list_iter_begin);
* actually release the connector when dropping our final reference.
*/
static void
-drm_connector_put_safe(struct drm_connector *conn)
+__drm_connector_put_safe(struct drm_connector *conn)
{
+ struct drm_mode_config *config = &conn->dev->mode_config;
+
+ lockdep_assert_held(&config->connector_list_lock);
+ list_add(&conn->free_head, &config->connector_free_list);
+
if (refcount_dec_and_test(&conn->base.refcount.refcount))
- schedule_work(&conn->free_work);
+ schedule_work(&config->connector_free_work);
}
/**
@@ -585,10 +597,10 @@ drm_connector_list_iter_next(struct drm_connector_list_iter *iter)
/* loop until it's not a zombie connector */
} while (!kref_get_unless_zero(&iter->conn->base.refcount));
- spin_unlock_irqrestore(&config->connector_list_lock, flags);
if (old_conn)
- drm_connector_put_safe(old_conn);
+ __drm_connector_put_safe(old_conn);
+ spin_unlock_irqrestore(&config->connector_list_lock, flags);
return iter->conn;
}
@@ -605,9 +617,15 @@ EXPORT_SYMBOL(drm_connector_list_iter_next);
*/
void drm_connector_list_iter_end(struct drm_connector_list_iter *iter)
{
+ struct drm_mode_config *config = &iter->dev->mode_config;
+ unsigned long flags;
+
iter->dev = NULL;
- if (iter->conn)
- drm_connector_put_safe(iter->conn);
+ if (iter->conn) {
+ spin_lock_irqsave(&config->connector_list_lock, flags);
+ __drm_connector_put_safe(iter->conn);
+ spin_unlock_irqrestore(&config->connector_list_lock, flags);
+ }
lock_release(&connector_list_iter_dep_map, 0, _RET_IP_);
}
EXPORT_SYMBOL(drm_connector_list_iter_end);
diff --git a/drivers/gpu/drm/drm_crtc_internal.h b/drivers/gpu/drm/drm_crtc_internal.h
index 9ebb8841778c..af00f42ba269 100644
--- a/drivers/gpu/drm/drm_crtc_internal.h
+++ b/drivers/gpu/drm/drm_crtc_internal.h
@@ -142,6 +142,7 @@ int drm_mode_connector_set_obj_prop(struct drm_mode_object *obj,
uint64_t value);
int drm_connector_create_standard_properties(struct drm_device *dev);
const char *drm_get_connector_force_name(enum drm_connector_force force);
+void drm_connector_free_work_fn(struct work_struct *work);
/* IOCTL */
int drm_mode_connector_property_set_ioctl(struct drm_device *dev,
diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c
index 6ffe952142e6..025fc23cf7c6 100644
--- a/drivers/gpu/drm/drm_mode_config.c
+++ b/drivers/gpu/drm/drm_mode_config.c
@@ -373,6 +373,7 @@ void drm_mode_config_init(struct drm_device *dev)
INIT_LIST_HEAD(&dev->mode_config.fb_list);
INIT_LIST_HEAD(&dev->mode_config.crtc_list);
INIT_LIST_HEAD(&dev->mode_config.connector_list);
+ INIT_LIST_HEAD(&dev->mode_config.connector_free_list);
INIT_LIST_HEAD(&dev->mode_config.encoder_list);
INIT_LIST_HEAD(&dev->mode_config.property_list);
INIT_LIST_HEAD(&dev->mode_config.property_blob_list);
@@ -382,6 +383,8 @@ void drm_mode_config_init(struct drm_device *dev)
ida_init(&dev->mode_config.connector_ida);
spin_lock_init(&dev->mode_config.connector_list_lock);
+ INIT_WORK(&dev->mode_config.connector_free_work, drm_connector_free_work_fn);
+
drm_mode_create_standard_properties(dev);
/* Just to be sure */
@@ -432,7 +435,7 @@ void drm_mode_config_cleanup(struct drm_device *dev)
}
drm_connector_list_iter_end(&conn_iter);
/* connector_iter drops references in a work item. */
- flush_scheduled_work();
+ flush_work(&dev->mode_config.connector_free_work);
if (WARN_ON(!list_empty(&dev->mode_config.connector_list))) {
drm_connector_list_iter_begin(dev, &conn_iter);
drm_for_each_connector_iter(connector, &conn_iter)
diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index ee3155391243..50bc21050fbf 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -966,12 +966,12 @@ struct drm_connector {
uint16_t tile_h_size, tile_v_size;
/**
- * @free_work:
+ * @free_head:
*
* Work used only by &drm_connector_iter to be able to clean up a
* connector from any context.
*/
- struct work_struct free_work;
+ struct list_head free_head;
};
#define obj_to_connector(x) container_of(x, struct drm_connector, base)
diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
index e5f3b43014e1..5e62e52a2c58 100644
--- a/include/drm/drm_mode_config.h
+++ b/include/drm/drm_mode_config.h
@@ -402,7 +402,7 @@ struct drm_mode_config {
/**
* @connector_list_lock: Protects @num_connector and
- * @connector_list.
+ * @connector_list and @connector_free_list.
*/
spinlock_t connector_list_lock;
/**
@@ -422,6 +422,21 @@ struct drm_mode_config {
* &struct drm_connector_list_iter to walk this list.
*/
struct list_head connector_list;
+ /**
+ * @connector_free_list:
+ *
+ * List of connector objects linked with &drm_connector.free_head.
+ * Protected by @connector_list_lock. Used by
+ * drm_for_each_connector_iter() and
+ * &struct drm_connector_list_iter to savely free connectors using
+ * @connector_free_work.
+ */
+ struct list_head connector_free_list;
+ /**
+ * @connector_free_work: Work to clean up @connector_free_list.
+ */
+ struct work_struct connector_free_work;
+
/**
* @num_encoder:
*
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
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