ipmi: Convert from tasklet to BH workqueue

The only generic interface to execute asynchronously in the BH context is
tasklet; however, it's marked deprecated and has some design flaws. To
replace tasklets, BH workqueue support was recently added. A BH workqueue
behaves similarly to regular workqueues except that the queued work items
are executed in the BH context.

This patch converts drivers/char/ipmi/* from tasklet to BH workqueue.

Based on the work done by Tejun Heo <tj@kernel.org>
Branch: https://git.kernel.org/pub/scm/linux/kernel/git/tj/wq.git for-6.10

Signed-off-by: Allen Pais <allen.lkml@gmail.com>
Message-Id: <20240327160314.9982-7-apais@linux.microsoft.com>
[Removed a duplicate include of workqueue.h]
Signed-off-by: Corey Minyard <minyard@acm.org>

Author: allenpais

drivers/char/ipmi/ipmi_msghandler.c

@@ -41,7 +41,7 @@
 
 static struct ipmi_recv_msg *ipmi_alloc_recv_msg(void);
 static int ipmi_init_msghandler(void);
-static void smi_recv_tasklet(struct tasklet_struct *t);
+static void smi_recv_work(struct work_struct *t);
 static void handle_new_recv_msgs(struct ipmi_smi *intf);
 static void need_waiter(struct ipmi_smi *intf);
 static int handle_one_recv_msg(struct ipmi_smi *intf,
@@ -498,13 +498,13 @@ struct ipmi_smi {
 	/*
 	 * Messages queued for delivery.  If delivery fails (out of memory
 	 * for instance), They will stay in here to be processed later in a
-	 * periodic timer interrupt.  The tasklet is for handling received
+	 * periodic timer interrupt.  The workqueue is for handling received
 	 * messages directly from the handler.
 	 */
 	spinlock_t       waiting_rcv_msgs_lock;
 	struct list_head waiting_rcv_msgs;
 	atomic_t	 watchdog_pretimeouts_to_deliver;
-	struct tasklet_struct recv_tasklet;
+	struct work_struct recv_work;
 
 	spinlock_t             xmit_msgs_lock;
 	struct list_head       xmit_msgs;
@@ -704,7 +704,7 @@ static void clean_up_interface_data(struct ipmi_smi *intf)
 	struct cmd_rcvr  *rcvr, *rcvr2;
 	struct list_head list;
 
-	tasklet_kill(&intf->recv_tasklet);
+	cancel_work_sync(&intf->recv_work);
 
 	free_smi_msg_list(&intf->waiting_rcv_msgs);
 	free_recv_msg_list(&intf->waiting_events);
@@ -1319,7 +1319,7 @@ static void free_user(struct kref *ref)
 {
 	struct ipmi_user *user = container_of(ref, struct ipmi_user, refcount);
 
-	/* SRCU cleanup must happen in task context. */
+	/* SRCU cleanup must happen in workqueue context. */
 	queue_work(remove_work_wq, &user->remove_work);
 }
 
@@ -3605,8 +3605,7 @@ int ipmi_add_smi(struct module         *owner,
 	intf->curr_seq = 0;
 	spin_lock_init(&intf->waiting_rcv_msgs_lock);
 	INIT_LIST_HEAD(&intf->waiting_rcv_msgs);
-	tasklet_setup(&intf->recv_tasklet,
-		     smi_recv_tasklet);
+	INIT_WORK(&intf->recv_work, smi_recv_work);
 	atomic_set(&intf->watchdog_pretimeouts_to_deliver, 0);
 	spin_lock_init(&intf->xmit_msgs_lock);
 	INIT_LIST_HEAD(&intf->xmit_msgs);
@@ -4779,7 +4778,7 @@ static void handle_new_recv_msgs(struct ipmi_smi *intf)
 			 * To preserve message order, quit if we
 			 * can't handle a message.  Add the message
 			 * back at the head, this is safe because this
-			 * tasklet is the only thing that pulls the
+			 * workqueue is the only thing that pulls the
 			 * messages.
 			 */
 			list_add(&smi_msg->link, &intf->waiting_rcv_msgs);
@@ -4812,10 +4811,10 @@ static void handle_new_recv_msgs(struct ipmi_smi *intf)
 	}
 }
 
-static void smi_recv_tasklet(struct tasklet_struct *t)
+static void smi_recv_work(struct work_struct *t)
 {
 	unsigned long flags = 0; /* keep us warning-free. */
-	struct ipmi_smi *intf = from_tasklet(intf, t, recv_tasklet);
+	struct ipmi_smi *intf = from_work(intf, t, recv_work);
 	int run_to_completion = intf->run_to_completion;
 	struct ipmi_smi_msg *newmsg = NULL;
 
@@ -4866,7 +4865,7 @@ void ipmi_smi_msg_received(struct ipmi_smi *intf,
 
 	/*
 	 * To preserve message order, we keep a queue and deliver from
-	 * a tasklet.
+	 * a workqueue.
 	 */
 	if (!run_to_completion)
 		spin_lock_irqsave(&intf->waiting_rcv_msgs_lock, flags);
@@ -4887,9 +4886,9 @@ void ipmi_smi_msg_received(struct ipmi_smi *intf,
 		spin_unlock_irqrestore(&intf->xmit_msgs_lock, flags);
 
 	if (run_to_completion)
-		smi_recv_tasklet(&intf->recv_tasklet);
+		smi_recv_work(&intf->recv_work);
 	else
-		tasklet_schedule(&intf->recv_tasklet);
+		queue_work(system_bh_wq, &intf->recv_work);
 }
 EXPORT_SYMBOL(ipmi_smi_msg_received);
 
@@ -4899,7 +4898,7 @@ void ipmi_smi_watchdog_pretimeout(struct ipmi_smi *intf)
 		return;
 
 	atomic_set(&intf->watchdog_pretimeouts_to_deliver, 1);
-	tasklet_schedule(&intf->recv_tasklet);
+	queue_work(system_bh_wq, &intf->recv_work);
 }
 EXPORT_SYMBOL(ipmi_smi_watchdog_pretimeout);
 
@@ -5068,7 +5067,7 @@ static bool ipmi_timeout_handler(struct ipmi_smi *intf,
 				       flags);
 	}
 
-	tasklet_schedule(&intf->recv_tasklet);
+	queue_work(system_bh_wq, &intf->recv_work);
 
 	return need_timer;
 }