[PATCH v2 04/24] drivers: hv: dxgkrnl: Creation of dxgdevice

From: Iouri Tarassov
Date: Fri Feb 04 2022 - 21:34:47 EST


A dxgdevice object represents a container of GPU allocations,
GPU sync objects, GPU contexts, etc. It belongs to a dxgadapter
object.

Signed-off-by: Iouri Tarassov <iourit@xxxxxxxxxxxxxxxxxxx>
---
drivers/hv/dxgkrnl/dxgadapter.c | 183 ++++++++++++++++++++++++++++++++
drivers/hv/dxgkrnl/dxgkrnl.h | 52 +++++++++
drivers/hv/dxgkrnl/dxgprocess.c | 43 ++++++++
drivers/hv/dxgkrnl/dxgvmbus.c | 54 ++++++++++
drivers/hv/dxgkrnl/ioctl.c | 134 +++++++++++++++++++++++
drivers/hv/dxgkrnl/misc.h | 1 +
6 files changed, 467 insertions(+)

diff --git a/drivers/hv/dxgkrnl/dxgadapter.c b/drivers/hv/dxgkrnl/dxgadapter.c
index 2c7823713547..c7e1dc55de49 100644
--- a/drivers/hv/dxgkrnl/dxgadapter.c
+++ b/drivers/hv/dxgkrnl/dxgadapter.c
@@ -199,6 +199,120 @@ void dxgadapter_release_lock_shared(struct dxgadapter *adapter)
up_read(&adapter->core_lock);
}

+struct dxgdevice *dxgdevice_create(struct dxgadapter *adapter,
+ struct dxgprocess *process)
+{
+ struct dxgdevice *device = vzalloc(sizeof(struct dxgdevice));
+ int ret;
+
+ if (device) {
+ kref_init(&device->device_kref);
+ device->adapter = adapter;
+ device->process = process;
+ kref_get(&adapter->adapter_kref);
+ init_rwsem(&device->device_lock);
+ INIT_LIST_HEAD(&device->pqueue_list_head);
+ device->object_state = DXGOBJECTSTATE_CREATED;
+ device->execution_state = _D3DKMT_DEVICEEXECUTION_ACTIVE;
+
+ ret = dxgprocess_adapter_add_device(process, adapter, device);
+ if (ret < 0) {
+ kref_put(&device->device_kref, dxgdevice_release);
+ device = NULL;
+ }
+ }
+ return device;
+}
+
+void dxgdevice_stop(struct dxgdevice *device)
+{
+}
+
+void dxgdevice_mark_destroyed(struct dxgdevice *device)
+{
+ down_write(&device->device_lock);
+ device->object_state = DXGOBJECTSTATE_DESTROYED;
+ up_write(&device->device_lock);
+}
+
+void dxgdevice_destroy(struct dxgdevice *device)
+{
+ struct dxgprocess *process = device->process;
+ struct dxgadapter *adapter = device->adapter;
+ struct d3dkmthandle device_handle = {};
+
+ pr_debug("%s: %p\n", __func__, device);
+
+ down_write(&device->device_lock);
+
+ if (device->object_state != DXGOBJECTSTATE_ACTIVE)
+ goto cleanup;
+
+ device->object_state = DXGOBJECTSTATE_DESTROYED;
+
+ dxgdevice_stop(device);
+
+ /* Guest handles need to be released before the host handles */
+ hmgrtable_lock(&process->handle_table, DXGLOCK_EXCL);
+ if (device->handle_valid) {
+ hmgrtable_free_handle(&process->handle_table,
+ HMGRENTRY_TYPE_DXGDEVICE, device->handle);
+ device_handle = device->handle;
+ device->handle_valid = 0;
+ }
+ hmgrtable_unlock(&process->handle_table, DXGLOCK_EXCL);
+
+ if (device_handle.v) {
+ up_write(&device->device_lock);
+ if (dxgadapter_acquire_lock_shared(adapter) == 0) {
+ dxgvmb_send_destroy_device(adapter, process,
+ device_handle);
+ dxgadapter_release_lock_shared(adapter);
+ }
+ down_write(&device->device_lock);
+ }
+
+cleanup:
+
+ if (device->adapter) {
+ dxgprocess_adapter_remove_device(device);
+ kref_put(&device->adapter->adapter_kref, dxgadapter_release);
+ }
+
+ up_write(&device->device_lock);
+
+ kref_put(&device->device_kref, dxgdevice_release);
+ pr_debug("dxgdevice_destroy_end\n");
+}
+
+int dxgdevice_acquire_lock_shared(struct dxgdevice *device)
+{
+ down_read(&device->device_lock);
+ if (!dxgdevice_is_active(device)) {
+ up_read(&device->device_lock);
+ return -ENODEV;
+ }
+ return 0;
+}
+
+void dxgdevice_release_lock_shared(struct dxgdevice *device)
+{
+ up_read(&device->device_lock);
+}
+
+bool dxgdevice_is_active(struct dxgdevice *device)
+{
+ return device->object_state == DXGOBJECTSTATE_ACTIVE;
+}
+
+void dxgdevice_release(struct kref *refcount)
+{
+ struct dxgdevice *device;
+
+ device = container_of(refcount, struct dxgdevice, device_kref);
+ vfree(device);
+}
+
struct dxgprocess_adapter *dxgprocess_adapter_create(struct dxgprocess *process,
struct dxgadapter *adapter)
{
@@ -213,6 +327,8 @@ struct dxgprocess_adapter *dxgprocess_adapter_create(struct dxgprocess *process,
adapter_info->adapter = adapter;
adapter_info->process = process;
adapter_info->refcount = 1;
+ mutex_init(&adapter_info->device_list_mutex);
+ INIT_LIST_HEAD(&adapter_info->device_list_head);
list_add_tail(&adapter_info->process_adapter_list_entry,
&process->process_adapter_list_head);
dxgadapter_add_process(adapter, adapter_info);
@@ -226,10 +342,32 @@ struct dxgprocess_adapter *dxgprocess_adapter_create(struct dxgprocess *process,

void dxgprocess_adapter_stop(struct dxgprocess_adapter *adapter_info)
{
+ struct dxgdevice *device;
+
+ mutex_lock(&adapter_info->device_list_mutex);
+ list_for_each_entry(device, &adapter_info->device_list_head,
+ device_list_entry) {
+ dxgdevice_stop(device);
+ }
+ mutex_unlock(&adapter_info->device_list_mutex);
}

void dxgprocess_adapter_destroy(struct dxgprocess_adapter *adapter_info)
{
+ struct dxgdevice *device;
+
+ mutex_lock(&adapter_info->device_list_mutex);
+ while (!list_empty(&adapter_info->device_list_head)) {
+ device = list_first_entry(&adapter_info->device_list_head,
+ struct dxgdevice, device_list_entry);
+ list_del(&device->device_list_entry);
+ device->device_list_entry.next = NULL;
+ mutex_unlock(&adapter_info->device_list_mutex);
+ dxgdevice_destroy(device);
+ mutex_lock(&adapter_info->device_list_mutex);
+ }
+ mutex_unlock(&adapter_info->device_list_mutex);
+
dxgadapter_remove_process(adapter_info);
kref_put(&adapter_info->adapter->adapter_kref, dxgadapter_release);
list_del(&adapter_info->process_adapter_list_entry);
@@ -247,3 +385,48 @@ void dxgprocess_adapter_release(struct dxgprocess_adapter *adapter_info)
if (adapter_info->refcount == 0)
dxgprocess_adapter_destroy(adapter_info);
}
+
+int dxgprocess_adapter_add_device(struct dxgprocess *process,
+ struct dxgadapter *adapter,
+ struct dxgdevice *device)
+{
+ struct dxgprocess_adapter *entry;
+ struct dxgprocess_adapter *adapter_info = NULL;
+ int ret = 0;
+
+ dxgglobal_acquire_process_adapter_lock();
+
+ list_for_each_entry(entry, &process->process_adapter_list_head,
+ process_adapter_list_entry) {
+ if (entry->adapter == adapter) {
+ adapter_info = entry;
+ break;
+ }
+ }
+ if (adapter_info == NULL) {
+ pr_err("failed to find process adapter info\n");
+ ret = -EINVAL;
+ goto cleanup;
+ }
+ mutex_lock(&adapter_info->device_list_mutex);
+ list_add_tail(&device->device_list_entry,
+ &adapter_info->device_list_head);
+ device->adapter_info = adapter_info;
+ mutex_unlock(&adapter_info->device_list_mutex);
+
+cleanup:
+
+ dxgglobal_release_process_adapter_lock();
+ return ret;
+}
+
+void dxgprocess_adapter_remove_device(struct dxgdevice *device)
+{
+ pr_debug("%s %p\n", __func__, device);
+ mutex_lock(&device->adapter_info->device_list_mutex);
+ if (device->device_list_entry.next) {
+ list_del(&device->device_list_entry);
+ device->device_list_entry.next = NULL;
+ }
+ mutex_unlock(&device->adapter_info->device_list_mutex);
+}
diff --git a/drivers/hv/dxgkrnl/dxgkrnl.h b/drivers/hv/dxgkrnl/dxgkrnl.h
index fbc15731cbd5..e0a433c36a06 100644
--- a/drivers/hv/dxgkrnl/dxgkrnl.h
+++ b/drivers/hv/dxgkrnl/dxgkrnl.h
@@ -29,6 +29,7 @@

struct dxgprocess;
struct dxgadapter;
+struct dxgdevice;

#include "misc.h"
#include "hmgr.h"
@@ -152,6 +153,9 @@ struct dxgprocess_adapter {
struct list_head adapter_process_list_entry;
/* Entry in dxgprocess::process_adapter_list_head */
struct list_head process_adapter_list_entry;
+ /* List of all dxgdevice objects created for the process on adapter */
+ struct list_head device_list_head;
+ struct mutex device_list_mutex;
struct dxgadapter *adapter;
struct dxgprocess *process;
int refcount;
@@ -161,6 +165,10 @@ struct dxgprocess_adapter *dxgprocess_adapter_create(struct dxgprocess *process,
struct dxgadapter
*adapter);
void dxgprocess_adapter_release(struct dxgprocess_adapter *adapter);
+int dxgprocess_adapter_add_device(struct dxgprocess *process,
+ struct dxgadapter *adapter,
+ struct dxgdevice *device);
+void dxgprocess_adapter_remove_device(struct dxgdevice *device);
void dxgprocess_adapter_stop(struct dxgprocess_adapter *adapter_info);
void dxgprocess_adapter_destroy(struct dxgprocess_adapter *adapter_info);

@@ -209,6 +217,11 @@ struct dxgadapter *dxgprocess_get_adapter(struct dxgprocess *process,
struct d3dkmthandle handle);
struct dxgadapter *dxgprocess_adapter_by_handle(struct dxgprocess *process,
struct d3dkmthandle handle);
+struct dxgdevice *dxgprocess_device_by_handle(struct dxgprocess *process,
+ struct d3dkmthandle handle);
+struct dxgdevice *dxgprocess_device_by_object_handle(struct dxgprocess *process,
+ enum hmgrentry_type t,
+ struct d3dkmthandle h);
void dxgprocess_ht_lock_shared_down(struct dxgprocess *process);
void dxgprocess_ht_lock_shared_up(struct dxgprocess *process);
void dxgprocess_ht_lock_exclusive_down(struct dxgprocess *process);
@@ -228,6 +241,7 @@ enum dxgadapter_state {
* This object represents the grapchis adapter.
* Objects, which take reference on the adapter:
* - dxgglobal
+ * - dxgdevice
* - adapter handle (struct d3dkmthandle)
*/
struct dxgadapter {
@@ -264,6 +278,38 @@ void dxgadapter_add_process(struct dxgadapter *adapter,
struct dxgprocess_adapter *process_info);
void dxgadapter_remove_process(struct dxgprocess_adapter *process_info);

+/*
+ * The object represent the device object.
+ * The following objects take reference on the device
+ * - device handle (struct d3dkmthandle)
+ */
+struct dxgdevice {
+ enum dxgobjectstate object_state;
+ /* Device takes reference on the adapter */
+ struct dxgadapter *adapter;
+ struct dxgprocess_adapter *adapter_info;
+ struct dxgprocess *process;
+ /* Entry in the DGXPROCESS_ADAPTER device list */
+ struct list_head device_list_entry;
+ struct kref device_kref;
+ /* Protects destcruction of the device object */
+ struct rw_semaphore device_lock;
+ /* List of paging queues. Protected by process handle table lock. */
+ struct list_head pqueue_list_head;
+ struct d3dkmthandle handle;
+ enum d3dkmt_deviceexecution_state execution_state;
+ u32 handle_valid;
+};
+
+struct dxgdevice *dxgdevice_create(struct dxgadapter *a, struct dxgprocess *p);
+void dxgdevice_destroy(struct dxgdevice *device);
+void dxgdevice_stop(struct dxgdevice *device);
+void dxgdevice_mark_destroyed(struct dxgdevice *device);
+int dxgdevice_acquire_lock_shared(struct dxgdevice *dev);
+void dxgdevice_release_lock_shared(struct dxgdevice *dev);
+void dxgdevice_release(struct kref *refcount);
+bool dxgdevice_is_active(struct dxgdevice *dev);
+
void init_ioctls(void);
long dxgk_compat_ioctl(struct file *f, unsigned int p1, unsigned long p2);
long dxgk_unlocked_ioctl(struct file *f, unsigned int p1, unsigned long p2);
@@ -297,6 +343,12 @@ int dxgvmb_send_destroy_process(struct d3dkmthandle process);
int dxgvmb_send_open_adapter(struct dxgadapter *adapter);
int dxgvmb_send_close_adapter(struct dxgadapter *adapter);
int dxgvmb_send_get_internal_adapter_info(struct dxgadapter *adapter);
+struct d3dkmthandle dxgvmb_send_create_device(struct dxgadapter *adapter,
+ struct dxgprocess *process,
+ struct d3dkmt_createdevice *args);
+int dxgvmb_send_destroy_device(struct dxgadapter *adapter,
+ struct dxgprocess *process,
+ struct d3dkmthandle h);
int dxgvmb_send_query_adapter_info(struct dxgprocess *process,
struct dxgadapter *adapter,
struct d3dkmt_queryadapterinfo *args);
diff --git a/drivers/hv/dxgkrnl/dxgprocess.c b/drivers/hv/dxgkrnl/dxgprocess.c
index 1fd7b7659792..734585689213 100644
--- a/drivers/hv/dxgkrnl/dxgprocess.c
+++ b/drivers/hv/dxgkrnl/dxgprocess.c
@@ -242,6 +242,49 @@ struct dxgadapter *dxgprocess_adapter_by_handle(struct dxgprocess *process,
return adapter;
}

+struct dxgdevice *dxgprocess_device_by_object_handle(struct dxgprocess *process,
+ enum hmgrentry_type t,
+ struct d3dkmthandle handle)
+{
+ struct dxgdevice *device = NULL;
+ void *obj;
+
+ hmgrtable_lock(&process->handle_table, DXGLOCK_SHARED);
+ obj = hmgrtable_get_object_by_type(&process->handle_table, t, handle);
+ if (obj) {
+ struct d3dkmthandle device_handle = {};
+
+ switch (t) {
+ case HMGRENTRY_TYPE_DXGDEVICE:
+ device = obj;
+ break;
+ default:
+ pr_err("invalid handle type: %d\n", t);
+ break;
+ }
+ if (device == NULL)
+ device = hmgrtable_get_object_by_type(
+ &process->handle_table,
+ HMGRENTRY_TYPE_DXGDEVICE,
+ device_handle);
+ if (device)
+ if (kref_get_unless_zero(&device->device_kref) == 0)
+ device = NULL;
+ }
+ if (device == NULL)
+ pr_err("device_by_handle failed: %d %x\n", t, handle.v);
+ hmgrtable_unlock(&process->handle_table, DXGLOCK_SHARED);
+ return device;
+}
+
+struct dxgdevice *dxgprocess_device_by_handle(struct dxgprocess *process,
+ struct d3dkmthandle handle)
+{
+ return dxgprocess_device_by_object_handle(process,
+ HMGRENTRY_TYPE_DXGDEVICE,
+ handle);
+}
+
void dxgprocess_ht_lock_shared_down(struct dxgprocess *process)
{
hmgrtable_lock(&process->handle_table, DXGLOCK_SHARED);
diff --git a/drivers/hv/dxgkrnl/dxgvmbus.c b/drivers/hv/dxgkrnl/dxgvmbus.c
index 8b8e0aa0fa5d..5b560754ac0d 100644
--- a/drivers/hv/dxgkrnl/dxgvmbus.c
+++ b/drivers/hv/dxgkrnl/dxgvmbus.c
@@ -656,6 +656,60 @@ int dxgvmb_send_get_internal_adapter_info(struct dxgadapter *adapter)
return ret;
}

+struct d3dkmthandle dxgvmb_send_create_device(struct dxgadapter *adapter,
+ struct dxgprocess *process,
+ struct d3dkmt_createdevice *args)
+{
+ int ret;
+ struct dxgkvmb_command_createdevice *command;
+ struct dxgkvmb_command_createdevice_return result = { };
+ struct dxgvmbusmsg msg;
+
+ ret = init_message(&msg, adapter, process, sizeof(*command));
+ if (ret)
+ goto cleanup;
+ command = (void *)msg.msg;
+
+ command_vgpu_to_host_init2(&command->hdr, DXGK_VMBCOMMAND_CREATEDEVICE,
+ process->host_handle);
+ command->flags = args->flags;
+
+ ret = dxgvmb_send_sync_msg(msg.channel, msg.hdr, msg.size,
+ &result, sizeof(result));
+ if (ret < 0)
+ result.device.v = 0;
+ free_message(&msg, process);
+cleanup:
+ if (ret)
+ pr_debug("err: %s %d", __func__, ret);
+ return result.device;
+}
+
+int dxgvmb_send_destroy_device(struct dxgadapter *adapter,
+ struct dxgprocess *process,
+ struct d3dkmthandle h)
+{
+ int ret;
+ struct dxgkvmb_command_destroydevice *command;
+ struct dxgvmbusmsg msg = {.hdr = NULL};
+
+ ret = init_message(&msg, adapter, process, sizeof(*command));
+ if (ret)
+ goto cleanup;
+ command = (void *)msg.msg;
+
+ command_vgpu_to_host_init2(&command->hdr, DXGK_VMBCOMMAND_DESTROYDEVICE,
+ process->host_handle);
+ command->device = h;
+
+ ret = dxgvmb_send_sync_msg_ntstatus(msg.channel, msg.hdr, msg.size);
+cleanup:
+ free_message(&msg, process);
+ if (ret)
+ pr_debug("err: %s %d", __func__, ret);
+ return ret;
+}
+
int dxgvmb_send_query_adapter_info(struct dxgprocess *process,
struct dxgadapter *adapter,
struct d3dkmt_queryadapterinfo *args)
diff --git a/drivers/hv/dxgkrnl/ioctl.c b/drivers/hv/dxgkrnl/ioctl.c
index 62a958f6f146..a6be88b6c792 100644
--- a/drivers/hv/dxgkrnl/ioctl.c
+++ b/drivers/hv/dxgkrnl/ioctl.c
@@ -437,6 +437,136 @@ dxgk_query_adapter_info(struct dxgprocess *process, void *__user inargs)
return ret;
}

+static int
+dxgk_create_device(struct dxgprocess *process, void *__user inargs)
+{
+ struct d3dkmt_createdevice args;
+ int ret;
+ struct dxgadapter *adapter = NULL;
+ struct dxgdevice *device = NULL;
+ struct d3dkmthandle host_device_handle = {};
+ bool adapter_locked = false;
+
+ pr_debug("ioctl: %s", __func__);
+
+ ret = copy_from_user(&args, inargs, sizeof(args));
+ if (ret) {
+ pr_err("%s failed to copy input args", __func__);
+ ret = -EINVAL;
+ goto cleanup;
+ }
+
+ /* The call acquires reference on the adapter */
+ adapter = dxgprocess_adapter_by_handle(process, args.adapter);
+ if (adapter == NULL) {
+ ret = -EINVAL;
+ goto cleanup;
+ }
+
+ device = dxgdevice_create(adapter, process);
+ if (device == NULL) {
+ ret = -ENOMEM;
+ goto cleanup;
+ }
+
+ ret = dxgadapter_acquire_lock_shared(adapter);
+ if (ret < 0)
+ goto cleanup;
+
+ adapter_locked = true;
+
+ host_device_handle = dxgvmb_send_create_device(adapter, process, &args);
+ if (host_device_handle.v) {
+ ret = copy_to_user(&((struct d3dkmt_createdevice *)inargs)->
+ device, &host_device_handle,
+ sizeof(struct d3dkmthandle));
+ if (ret) {
+ pr_err("%s failed to copy device handle", __func__);
+ ret = -EINVAL;
+ goto cleanup;
+ }
+
+ hmgrtable_lock(&process->handle_table, DXGLOCK_EXCL);
+ ret = hmgrtable_assign_handle(&process->handle_table, device,
+ HMGRENTRY_TYPE_DXGDEVICE,
+ host_device_handle);
+ if (ret >= 0) {
+ device->handle = host_device_handle;
+ device->handle_valid = 1;
+ device->object_state = DXGOBJECTSTATE_ACTIVE;
+ }
+ hmgrtable_unlock(&process->handle_table, DXGLOCK_EXCL);
+ }
+
+cleanup:
+
+ if (ret < 0) {
+ if (host_device_handle.v)
+ dxgvmb_send_destroy_device(adapter, process,
+ host_device_handle);
+ if (device)
+ dxgdevice_destroy(device);
+ }
+
+ if (adapter_locked)
+ dxgadapter_release_lock_shared(adapter);
+
+ if (adapter)
+ kref_put(&adapter->adapter_kref, dxgadapter_release);
+
+ pr_debug("ioctl:%s %s %d", errorstr(ret), __func__, ret);
+ return ret;
+}
+
+static int
+dxgk_destroy_device(struct dxgprocess *process, void *__user inargs)
+{
+ struct d3dkmt_destroydevice args;
+ int ret;
+ struct dxgadapter *adapter = NULL;
+ struct dxgdevice *device = NULL;
+
+ pr_debug("ioctl: %s", __func__);
+
+ ret = copy_from_user(&args, inargs, sizeof(args));
+ if (ret) {
+ pr_err("%s failed to copy input args", __func__);
+ ret = -EINVAL;
+ goto cleanup;
+ }
+
+ hmgrtable_lock(&process->handle_table, DXGLOCK_EXCL);
+ device = hmgrtable_get_object_by_type(&process->handle_table,
+ HMGRENTRY_TYPE_DXGDEVICE,
+ args.device);
+ if (device) {
+ hmgrtable_free_handle(&process->handle_table,
+ HMGRENTRY_TYPE_DXGDEVICE, args.device);
+ device->handle_valid = 0;
+ }
+ hmgrtable_unlock(&process->handle_table, DXGLOCK_EXCL);
+
+ if (device == NULL) {
+ pr_err("invalid device handle: %x", args.device.v);
+ ret = -EINVAL;
+ goto cleanup;
+ }
+
+ adapter = device->adapter;
+
+ dxgdevice_destroy(device);
+
+ if (dxgadapter_acquire_lock_shared(adapter) == 0) {
+ dxgvmb_send_destroy_device(adapter, process, args.device);
+ dxgadapter_release_lock_shared(adapter);
+ }
+
+cleanup:
+
+ pr_debug("ioctl:%s %s %d", errorstr(ret), __func__, ret);
+ return ret;
+}
+
/*
* IOCTL processing
* The driver IOCTLs return
@@ -495,12 +625,16 @@ void init_ioctls(void)
{
SET_IOCTL(/*0x1 */ dxgk_open_adapter_from_luid,
LX_DXOPENADAPTERFROMLUID);
+ SET_IOCTL(/*0x2 */ dxgk_create_device,
+ LX_DXCREATEDEVICE);
SET_IOCTL(/*0x9 */ dxgk_query_adapter_info,
LX_DXQUERYADAPTERINFO);
SET_IOCTL(/*0x14 */ dxgk_enum_adapters,
LX_DXENUMADAPTERS2);
SET_IOCTL(/*0x15 */ dxgk_close_adapter,
LX_DXCLOSEADAPTER);
+ SET_IOCTL(/*0x19 */ dxgk_destroy_device,
+ LX_DXDESTROYDEVICE);
SET_IOCTL(/*0x3e */ dxgk_enum_adapters3,
LX_DXENUMADAPTERS3);
}
diff --git a/drivers/hv/dxgkrnl/misc.h b/drivers/hv/dxgkrnl/misc.h
index d00e7cc00470..8948f48ec9dc 100644
--- a/drivers/hv/dxgkrnl/misc.h
+++ b/drivers/hv/dxgkrnl/misc.h
@@ -25,6 +25,7 @@ extern const struct d3dkmthandle zerohandle;
* The higher enum value, the higher is the lock order.
* When a lower lock ois held, the higher lock should not be acquired.
*
+ * device_list_mutex
* channel_lock
* fd_mutex
* plistmutex
--
2.35.1