Bluetooth: Add helper for serialized HCI command execution

The usage of __hci_cmd_sync() within the hdev->setup() callback allows for
a nice and simple serialized execution of HCI commands. More importantly
it allows for result processing before issueing the next command.

With the current usage of hci_req_run() it is possible to batch up
commands and execute them, but it is impossible to react to their
results or errors.

This is an attempt to generalize the hdev->setup() handling and provide
a simple way of running multiple HCI commands from a single function
context.

There are multiple struct work that are decdicated to certain tasks
already used right now. It is add a lot of bloat to hci_dev struct and
extra handling code. So it might be possible to put all of these behind
a common HCI command infrastructure and just execute the HCI commands
from the same work context in a serialized fashion.

For example updating the white list and resolving list can be done now
without having to know the list size ahead of time. Also preparing for
suspend or resume shouldn't require a state machine anymore. There are
other tasks that should be simplified as well.

Signed-off-by: Marcel Holtmann <[email protected]>
Signed-off-by: Luiz Augusto von Dentz <[email protected]>
Signed-off-by: Marcel Holtmann <[email protected]>

Author: holtmann

include/net/bluetooth/hci_core.h

@@ -30,6 +30,7 @@
 #include <linux/rculist.h>
 
 #include <net/bluetooth/hci.h>
+#include <net/bluetooth/hci_sync.h>
 #include <net/bluetooth/hci_sock.h>
 
 /* HCI priority */
@@ -475,6 +476,9 @@ struct hci_dev {
 	struct work_struct	power_on;
 	struct delayed_work	power_off;
 	struct work_struct	error_reset;
+	struct work_struct	cmd_sync_work;
+	struct list_head	cmd_sync_work_list;
+	struct mutex		cmd_sync_work_lock;
 
 	__u16			discov_timeout;
 	struct delayed_work	discov_off;
@@ -1690,10 +1694,6 @@ static inline int hci_check_conn_params(u16 min, u16 max, u16 latency,
 int hci_register_cb(struct hci_cb *hcb);
 int hci_unregister_cb(struct hci_cb *hcb);
 
-struct sk_buff *__hci_cmd_sync(struct hci_dev *hdev, u16 opcode, u32 plen,
-			       const void *param, u32 timeout);
-struct sk_buff *__hci_cmd_sync_ev(struct hci_dev *hdev, u16 opcode, u32 plen,
-				  const void *param, u8 event, u32 timeout);
 int __hci_cmd_send(struct hci_dev *hdev, u16 opcode, u32 plen,
 		   const void *param);
 
@@ -1704,9 +1704,6 @@ void hci_send_sco(struct hci_conn *conn, struct sk_buff *skb);
 
 void *hci_sent_cmd_data(struct hci_dev *hdev, __u16 opcode);
 
-struct sk_buff *hci_cmd_sync(struct hci_dev *hdev, u16 opcode, u32 plen,
-			     const void *param, u32 timeout);
-
 u32 hci_conn_get_phy(struct hci_conn *conn);
 
 /* ----- HCI Sockets ----- */

include/net/bluetooth/hci_sync.h

@@ -0,0 +1,42 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * BlueZ - Bluetooth protocol stack for Linux
+ *
+ * Copyright (C) 2021 Intel Corporation
+ */
+
+typedef int (*hci_cmd_sync_work_func_t)(struct hci_dev *hdev, void *data);
+typedef void (*hci_cmd_sync_work_destroy_t)(struct hci_dev *hdev, void *data,
+					    int err);
+
+struct hci_cmd_sync_work_entry {
+	struct list_head list;
+	hci_cmd_sync_work_func_t func;
+	void *data;
+	hci_cmd_sync_work_destroy_t destroy;
+};
+
+/* Function with sync suffix shall not be called with hdev->lock held as they
+ * wait the command to complete and in the meantime an event could be received
+ * which could attempt to acquire hdev->lock causing a deadlock.
+ */
+struct sk_buff *__hci_cmd_sync(struct hci_dev *hdev, u16 opcode, u32 plen,
+			       const void *param, u32 timeout);
+struct sk_buff *hci_cmd_sync(struct hci_dev *hdev, u16 opcode, u32 plen,
+			     const void *param, u32 timeout);
+struct sk_buff *__hci_cmd_sync_ev(struct hci_dev *hdev, u16 opcode, u32 plen,
+				  const void *param, u8 event, u32 timeout);
+struct sk_buff *__hci_cmd_sync_sk(struct hci_dev *hdev, u16 opcode, u32 plen,
+				  const void *param, u8 event, u32 timeout,
+				  struct sock *sk);
+int __hci_cmd_sync_status(struct hci_dev *hdev, u16 opcode, u32 plen,
+			  const void *param, u32 timeout);
+int __hci_cmd_sync_status_sk(struct hci_dev *hdev, u16 opcode, u32 plen,
+			     const void *param, u8 event, u32 timeout,
+			     struct sock *sk);
+
+void hci_cmd_sync_init(struct hci_dev *hdev);
+void hci_cmd_sync_clear(struct hci_dev *hdev);
+
+int hci_cmd_sync_queue(struct hci_dev *hdev, hci_cmd_sync_work_func_t func,
+		       void *data, hci_cmd_sync_work_destroy_t destroy);

net/bluetooth/Makefile

@@ -15,7 +15,7 @@ bluetooth_6lowpan-y := 6lowpan.o
 bluetooth-y := af_bluetooth.o hci_core.o hci_conn.o hci_event.o mgmt.o \
 	hci_sock.o hci_sysfs.o l2cap_core.o l2cap_sock.o smp.o lib.o \
 	ecdh_helper.o hci_request.o mgmt_util.o mgmt_config.o hci_codec.o \
-	eir.o
+	eir.o hci_sync.o
 
 bluetooth-$(CONFIG_BT_BREDR) += sco.o
 bluetooth-$(CONFIG_BT_HS) += a2mp.o amp.o

net/bluetooth/hci_core.c

@@ -3747,6 +3747,8 @@ struct hci_dev *hci_alloc_dev_priv(int sizeof_priv)
 	INIT_WORK(&hdev->error_reset, hci_error_reset);
 	INIT_WORK(&hdev->suspend_prepare, hci_prepare_suspend);
 
+	hci_cmd_sync_init(hdev);
+
 	INIT_DELAYED_WORK(&hdev->power_off, hci_power_off);
 
 	skb_queue_head_init(&hdev->rx_q);
@@ -3905,6 +3907,8 @@ void hci_unregister_dev(struct hci_dev *hdev)
 
 	cancel_work_sync(&hdev->power_on);
 
+	hci_cmd_sync_clear(hdev);
+
 	if (!test_bit(HCI_QUIRK_NO_SUSPEND_NOTIFIER, &hdev->quirks)) {
 		hci_suspend_clear_tasks(hdev);
 		unregister_pm_notifier(&hdev->suspend_notifier);
@@ -4271,25 +4275,6 @@ void *hci_sent_cmd_data(struct hci_dev *hdev, __u16 opcode)
 	return hdev->sent_cmd->data + HCI_COMMAND_HDR_SIZE;
 }
 
-/* Send HCI command and wait for command complete event */
-struct sk_buff *hci_cmd_sync(struct hci_dev *hdev, u16 opcode, u32 plen,
-			     const void *param, u32 timeout)
-{
-	struct sk_buff *skb;
-
-	if (!test_bit(HCI_UP, &hdev->flags))
-		return ERR_PTR(-ENETDOWN);
-
-	bt_dev_dbg(hdev, "opcode 0x%4.4x plen %d", opcode, plen);
-
-	hci_req_sync_lock(hdev);
-	skb = __hci_cmd_sync(hdev, opcode, plen, param, timeout);
-	hci_req_sync_unlock(hdev);
-
-	return skb;
-}
-EXPORT_SYMBOL(hci_cmd_sync);
-
 /* Send ACL data */
 static void hci_add_acl_hdr(struct sk_buff *skb, __u16 handle, __u16 flags)
 {

net/bluetooth/hci_request.c

@@ -32,10 +32,6 @@
 #include "msft.h"
 #include "eir.h"
 
-#define HCI_REQ_DONE	  0
-#define HCI_REQ_PEND	  1
-#define HCI_REQ_CANCELED  2
-
 void hci_req_init(struct hci_request *req, struct hci_dev *hdev)
 {
 	skb_queue_head_init(&req->cmd_q);
@@ -126,70 +122,6 @@ void hci_req_sync_cancel(struct hci_dev *hdev, int err)
 	}
 }
 
-struct sk_buff *__hci_cmd_sync_ev(struct hci_dev *hdev, u16 opcode, u32 plen,
-				  const void *param, u8 event, u32 timeout)
-{
-	struct hci_request req;
-	struct sk_buff *skb;
-	int err = 0;
-
-	bt_dev_dbg(hdev, "");
-
-	hci_req_init(&req, hdev);
-
-	hci_req_add_ev(&req, opcode, plen, param, event);
-
-	hdev->req_status = HCI_REQ_PEND;
-
-	err = hci_req_run_skb(&req, hci_req_sync_complete);
-	if (err < 0)
-		return ERR_PTR(err);
-
-	err = wait_event_interruptible_timeout(hdev->req_wait_q,
-			hdev->req_status != HCI_REQ_PEND, timeout);
-
-	if (err == -ERESTARTSYS)
-		return ERR_PTR(-EINTR);
-
-	switch (hdev->req_status) {
-	case HCI_REQ_DONE:
-		err = -bt_to_errno(hdev->req_result);
-		break;
-
-	case HCI_REQ_CANCELED:
-		err = -hdev->req_result;
-		break;
-
-	default:
-		err = -ETIMEDOUT;
-		break;
-	}
-
-	hdev->req_status = hdev->req_result = 0;
-	skb = hdev->req_skb;
-	hdev->req_skb = NULL;
-
-	bt_dev_dbg(hdev, "end: err %d", err);
-
-	if (err < 0) {
-		kfree_skb(skb);
-		return ERR_PTR(err);
-	}
-
-	if (!skb)
-		return ERR_PTR(-ENODATA);
-
-	return skb;
-}
-EXPORT_SYMBOL(__hci_cmd_sync_ev);
-
-struct sk_buff *__hci_cmd_sync(struct hci_dev *hdev, u16 opcode, u32 plen,
-			       const void *param, u32 timeout)
-{
-	return __hci_cmd_sync_ev(hdev, opcode, plen, param, 0, timeout);
-}
-EXPORT_SYMBOL(__hci_cmd_sync);
-
 /* Execute request and wait for completion. */
 int __hci_req_sync(struct hci_dev *hdev, int (*func)(struct hci_request *req,
 						     unsigned long opt),

net/bluetooth/hci_request.h

@@ -25,6 +25,10 @@
 #define hci_req_sync_lock(hdev)   mutex_lock(&hdev->req_lock)
 #define hci_req_sync_unlock(hdev) mutex_unlock(&hdev->req_lock)
 
+#define HCI_REQ_DONE	  0
+#define HCI_REQ_PEND	  1
+#define HCI_REQ_CANCELED  2
+
 struct hci_request {
 	struct hci_dev		*hdev;
 	struct sk_buff_head	cmd_q;