[SCSI] bnx2i: Added the use of kthreads to handle SCSI cmd completion

This patch breaks the SCSI cmd completion into two parts:
1. The bh will allocate and queued work to the cmd specific CPU IO
completion kthread.  The CPU for the cmd is from the sc->request->cpu.

2. The CPU specific IO completion kthread will call the scsi_cmd_resp
routine to do the actual cmd completion.

In the normal case, these IO completion kthreads should complete before
the blk IO times out at 60s.  However, in the case when these kthreads
are blocked for whatever reason and exceeded the timeout, the call
to conn_destroy will have to iterate and exhaust all related work in the
percpu work list for all online CPUs.  This will guarantee the protection
of the work->session and conn pointers before they get freed.

Also modified the event coalescing formula to have at least the
event_coal_min outstanding cmds in the pipeline so the SCSI producer
would not get underrun.

Also changed the following SCSI parameters:
- can_queue from 1024 to 2048
- cmds_per_lun from 24 to 128

Signed-off-by: Eddie Wai <eddie.wai@broadcom.com>
Acked-by: Benjamin Li <benli@broadcom.com>
Acked-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

1 files changed, 117 insertions, 1 deletions

diff --git a/drivers/scsi/bnx2i/bnx2i_init.c b/drivers/scsi/bnx2i/bnx2i_init.c
index 6adbdc3..0f7fb14 100644
--- a/drivers/scsi/bnx2i/bnx2i_init.c
+++ b/drivers/scsi/bnx2i/bnx2i_init.c
@@ -40,7 +40,7 @@ unsigned int event_coal_min = 24;
 module_param(event_coal_min, int, 0664);
 MODULE_PARM_DESC(event_coal_min, "Event Coalescing Minimum Commands");
 
-unsigned int event_coal_div = 1;
+unsigned int event_coal_div = 2;
 module_param(event_coal_div, int, 0664);
 MODULE_PARM_DESC(event_coal_div, "Event Coalescing Divide Factor");
 
@@ -66,6 +66,15 @@ MODULE_PARM_DESC(rq_size, "Configure RQ size");
 
 u64 iscsi_error_mask = 0x00;
 
+DEFINE_PER_CPU(struct bnx2i_percpu_s, bnx2i_percpu);
+
+static int bnx2i_cpu_callback(struct notifier_block *nfb,
+			      unsigned long action, void *hcpu);
+/* notification function for CPU hotplug events */
+static struct notifier_block bnx2i_cpu_notifier = {
+	.notifier_call = bnx2i_cpu_callback,
+};
+
 
 /**
  * bnx2i_identify_device - identifies NetXtreme II device type
@@ -362,6 +371,91 @@ void bnx2i_ulp_exit(struct cnic_dev *dev)
 
 
 /**
+ * bnx2i_percpu_thread_create - Create a receive thread for an
+ *				online CPU
+ *
+ * @cpu:	cpu index for the online cpu
+ */
+static void bnx2i_percpu_thread_create(unsigned int cpu)
+{
+	struct bnx2i_percpu_s *p;
+	struct task_struct *thread;
+
+	p = &per_cpu(bnx2i_percpu, cpu);
+
+	thread = kthread_create(bnx2i_percpu_io_thread, (void *)p,
+				"bnx2i_thread/%d", cpu);
+	/* bind thread to the cpu */
+	if (likely(!IS_ERR(thread))) {
+		kthread_bind(thread, cpu);
+		p->iothread = thread;
+		wake_up_process(thread);
+	}
+}
+
+
+static void bnx2i_percpu_thread_destroy(unsigned int cpu)
+{
+	struct bnx2i_percpu_s *p;
+	struct task_struct *thread;
+	struct bnx2i_work *work, *tmp;
+
+	/* Prevent any new work from being queued for this CPU */
+	p = &per_cpu(bnx2i_percpu, cpu);
+	spin_lock_bh(&p->p_work_lock);
+	thread = p->iothread;
+	p->iothread = NULL;
+
+	/* Free all work in the list */
+	list_for_each_entry_safe(work, tmp, &p->work_list, list) {
+		list_del_init(&work->list);
+		bnx2i_process_scsi_cmd_resp(work->session,
+					    work->bnx2i_conn, &work->cqe);
+		kfree(work);
+	}
+
+	spin_unlock_bh(&p->p_work_lock);
+	if (thread)
+		kthread_stop(thread);
+}
+
+
+/**
+ * bnx2i_cpu_callback - Handler for CPU hotplug events
+ *
+ * @nfb:	The callback data block
+ * @action:	The event triggering the callback
+ * @hcpu:	The index of the CPU that the event is for
+ *
+ * This creates or destroys per-CPU data for iSCSI
+ *
+ * Returns NOTIFY_OK always.
+ */
+static int bnx2i_cpu_callback(struct notifier_block *nfb,
+			      unsigned long action, void *hcpu)
+{
+	unsigned cpu = (unsigned long)hcpu;
+
+	switch (action) {
+	case CPU_ONLINE:
+	case CPU_ONLINE_FROZEN:
+		printk(KERN_INFO "bnx2i: CPU %x online: Create Rx thread\n",
+			cpu);
+		bnx2i_percpu_thread_create(cpu);
+		break;
+	case CPU_DEAD:
+	case CPU_DEAD_FROZEN:
+		printk(KERN_INFO "CPU %x offline: Remove Rx thread\n", cpu);
+		bnx2i_percpu_thread_destroy(cpu);
+		break;
+	default:
+		break;
+	}
+	return NOTIFY_OK;
+}
+
+
+/**
  * bnx2i_mod_init - module init entry point
  *
  * initialize any driver wide global data structures such as endpoint pool,
@@ -371,6 +465,8 @@ void bnx2i_ulp_exit(struct cnic_dev *dev)
 static int __init bnx2i_mod_init(void)
 {
 	int err;
+	unsigned cpu = 0;
+	struct bnx2i_percpu_s *p;
 
 	printk(KERN_INFO "%s", version);
 
@@ -393,6 +489,20 @@ static int __init bnx2i_mod_init(void)
 		goto unreg_xport;
 	}
 
+	/* Create percpu kernel threads to handle iSCSI I/O completions */
+	for_each_possible_cpu(cpu) {
+		p = &per_cpu(bnx2i_percpu, cpu);
+		INIT_LIST_HEAD(&p->work_list);
+		spin_lock_init(&p->p_work_lock);
+		p->iothread = NULL;
+	}
+
+	for_each_online_cpu(cpu)
+		bnx2i_percpu_thread_create(cpu);
+
+	/* Initialize per CPU interrupt thread */
+	register_hotcpu_notifier(&bnx2i_cpu_notifier);
+
 	return 0;
 
 unreg_xport:
@@ -413,6 +523,7 @@ out:
 static void __exit bnx2i_mod_exit(void)
 {
 	struct bnx2i_hba *hba;
+	unsigned cpu = 0;
 
 	mutex_lock(&bnx2i_dev_lock);
 	while (!list_empty(&adapter_list)) {
@@ -430,6 +541,11 @@ static void __exit bnx2i_mod_exit(void)
 	}
 	mutex_unlock(&bnx2i_dev_lock);
 
+	unregister_hotcpu_notifier(&bnx2i_cpu_notifier);
+
+	for_each_online_cpu(cpu)
+		bnx2i_percpu_thread_destroy(cpu);
+
 	iscsi_unregister_transport(&bnx2i_iscsi_transport);
 	cnic_unregister_driver(CNIC_ULP_ISCSI);
 }