[patch v2 17/37] add rxe_task.c

[rpearson-klaOcWyJdxkshyMvu7JE4pqQE7yCjDx5@public.gmane.org]

[-- Attachment #1: add-rxe_task.c --]
[-- Type: text/plain, Size: 5072 bytes --]

Tasklet handling details.

Signed-off-by: Bob Pearson <rpearson-klaOcWyJdxkshyMvu7JE4pqQE7yCjDx5@public.gmane.org>

---
 drivers/infiniband/hw/rxe/rxe_task.c |  169 +++++++++++++++++++++++++++++++++++
 1 file changed, 169 insertions(+)

Index: infiniband/drivers/infiniband/hw/rxe/rxe_task.c
===================================================================
--- /dev/null
+++ infiniband/drivers/infiniband/hw/rxe/rxe_task.c
@@ -0,0 +1,169 @@
+/*
+ * Copyright (c) 2009-2011 Mellanox Technologies Ltd. All rights reserved.
+ * Copyright (c) 2009-2011 System Fabric Works, Inc. All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *	   Redistribution and use in source and binary forms, with or
+ *	   without modification, are permitted provided that the following
+ *	   conditions are met:
+ *
+ *	- Redistributions of source code must retain the above
+ *	  copyright notice, this list of conditions and the following
+ *	  disclaimer.
+ *
+ *	- Redistributions in binary form must reproduce the above
+ *	  copyright notice, this list of conditions and the following
+ *	  disclaimer in the documentation and/or other materials
+ *	  provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include <linux/kernel.h>
+#include <linux/interrupt.h>
+#include <linux/hardirq.h>
+
+#include "rxe_task.h"
+
+int __rxe_do_task(struct rxe_task *task)
+
+{
+	int ret;
+
+	while ((ret = task->func(task->arg)) == 0)
+		;
+
+	task->ret = ret;
+
+	return ret;
+}
+
+/*
+ * this locking is due to a potential race where
+ * a second caller finds the task already running
+ * but looks just after the last call to func
+ */
+void rxe_do_task(unsigned long data)
+{
+	int cont;
+	int ret;
+	unsigned long flags;
+	struct rxe_task *task = (struct rxe_task *)data;
+
+	spin_lock_irqsave(&task->state_lock, flags);
+	switch (task->state) {
+	case TASK_STATE_START:
+		task->state = TASK_STATE_BUSY;
+		spin_unlock_irqrestore(&task->state_lock, flags);
+		break;
+
+	case TASK_STATE_BUSY:
+		task->state = TASK_STATE_ARMED;
+		/* fall through to */
+	case TASK_STATE_ARMED:
+		spin_unlock_irqrestore(&task->state_lock, flags);
+		return;
+
+	default:
+		spin_unlock_irqrestore(&task->state_lock, flags);
+		pr_warn("bad state = %d in rxe_do_task\n", task->state);
+		return;
+	}
+
+	do {
+		cont = 0;
+		ret = task->func(task->arg);
+
+		spin_lock_irqsave(&task->state_lock, flags);
+		switch (task->state) {
+		case TASK_STATE_BUSY:
+			if (ret)
+				task->state = TASK_STATE_START;
+			else
+				cont = 1;
+			break;
+
+		/* soneone tried to run the task since the
+		   last time we called func, so we will call
+		   one more time regardless of the return value */
+		case TASK_STATE_ARMED:
+			task->state = TASK_STATE_BUSY;
+			cont = 1;
+			break;
+
+		default:
+			pr_warn("bad state = %d in rxe_do_task\n",
+				task->state);
+		}
+		spin_unlock_irqrestore(&task->state_lock, flags);
+	} while (cont);
+
+	task->ret = ret;
+}
+
+int rxe_init_task(void *obj, struct rxe_task *task, int *fast,
+		  void *arg, int (*func)(void *), char *name)
+{
+	task->obj	= obj;
+	task->fast	= fast;
+	task->arg	= arg;
+	task->func	= func;
+	snprintf(task->name, sizeof(task->name), "%s", name);
+
+	tasklet_init(&task->tasklet, rxe_do_task, (unsigned long)task);
+
+	task->state = TASK_STATE_START;
+	spin_lock_init(&task->state_lock);
+
+	return 0;
+}
+
+void rxe_cleanup_task(struct rxe_task *task)
+{
+	tasklet_kill(&task->tasklet);
+}
+
+/*
+ * depending on value of fast allow bypassing
+ * tasklet call or not
+ *	 0 => never
+ *	 1 => only if not in interrupt level
+ *	>1 => always
+ */
+static inline int rxe_fast_path_ok(int fast)
+{
+	if (fast == 0 || (fast == 1 && (in_irq() || irqs_disabled())))
+		return 0;
+	else
+		return 1;
+}
+
+void rxe_run_task(struct rxe_task *task, int sched)
+{
+	if (sched || !rxe_fast_path_ok(*task->fast))
+		tasklet_schedule(&task->tasklet);
+	else
+		rxe_do_task((unsigned long)task);
+}
+
+void rxe_disable_task(struct rxe_task *task)
+{
+	tasklet_disable(&task->tasklet);
+}
+
+void rxe_enable_task(struct rxe_task *task)
+{
+	tasklet_enable(&task->tasklet);
+}


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