>From 7ea29ebb151f4822b3091c018b3b6401f2a36e3e Mon Sep 17 00:00:00 2001
From: Huang Ying <ying.huang@intel.com>
Date: Fri, 2 Jul 2010 13:51:45 +0800
Subject: [PATCH 09/30] kfifo_sample

---
 kernel/Makefile       |    1 
 kernel/kfifo_sample.c |  125 ++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 126 insertions(+)
 create mode 100644 kernel/kfifo_sample.c

--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -104,6 +104,7 @@ obj-$(CONFIG_PERF_EVENTS) += perf_event.
 obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o
 obj-$(CONFIG_USER_RETURN_NOTIFIER) += user-return-notifier.o
 obj-$(CONFIG_PADATA) += padata.o
+obj-m += kfifo_sample.o
 
 ifneq ($(CONFIG_SCHED_OMIT_FRAME_POINTER),y)
 # According to Alan Modra <alan@linuxcare.com.au>, the -fno-omit-frame-pointer is
--- /dev/null
+++ b/kernel/kfifo_sample.c
@@ -0,0 +1,125 @@
+/* kfifo_sample.c */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/kfifo.h>
+#include <linux/percpu.h>
+
+enum record_type {
+	/* The record is just a pad in fifo, no valid data */
+	RECORD_TYPE_PAD = 0x1,
+	RECORD_TYPE_NMI = 0x2,
+	RECORD_TYPE_IRQ = 0x3,
+};
+
+/* Variable length data structure to put into fifo */
+struct base_record {
+	unsigned short len;
+	unsigned short type;
+	unsigned char data[0];
+};
+
+/* Data collected in NMI handler */
+struct nmi_record {
+	struct base_record base;
+	int nmi_field1;
+	int nmi_field2;
+};
+
+/* Data collected in IRQ handler */
+struct irq_record {
+	struct base_record base;
+	int irq_field1;
+};
+
+static DEFINE_PER_CPU(struct kfifo, fifos);
+
+int record_fifo_write(unsigned int len,
+		      void (*fill_data)(struct base_record *rcd))
+{
+	struct kfifo *fifo;
+	struct base_record *rcd;
+	unsigned int rlen;
+	int rc = 0;
+
+	fifo = &get_cpu_var(fifos);
+	for (;;) {
+		rlen = len;
+		rcd = kfifo_reserve_continuous_ptr(fifo, &rlen);
+		/* Overflow, this record is thrown away */
+		if (!rcd) {
+			rc = -ENOBUFS;
+			goto out;
+		}
+		/*
+		 * Continuous space is not big enough, the requested
+		 * space will be marked as pad, then retry
+		 */
+		if (rlen != len) {
+			rcd->len = rlen;
+			rcd->type = RECORD_TYPE_PAD;
+			kfifo_commit_ptr(fifo, rcd);
+		} else {
+			rcd->len = len;
+			/* Fill other fields */
+			fill_data(rcd);
+			kfifo_commit_ptr(fifo, rcd);
+			break;
+		}
+	}
+out:
+	put_cpu_var(fifos);
+	return rc;
+}
+
+void nmi_fill_data(struct base_record *rcd)
+{
+	struct nmi_record *nmi_rcd = (struct nmi_record *)rcd;
+
+	rcd->type = RECORD_TYPE_NMI;
+	/* Fill other NMI specific field */
+}
+
+void nmi_handler(void)
+{
+	record_fifo_write(sizeof(struct nmi_record), nmi_fill_data);
+	/* other processing */
+}
+
+void irq_fill_data(struct base_record *rcd)
+{
+	struct irq_record *irq_rcd = (struct irq_record *)rcd;
+
+	rcd->type = RECORD_TYPE_IRQ;
+	/* Fill other IRQ specific field */
+}
+
+void irq_handler(void)
+{
+	record_fifo_write(sizeof(struct irq_record), irq_fill_data);
+	/* other processing */
+}
+
+int record_fifo_for_each(int (*func)(struct base_record *rcd))
+{
+	struct kfifo *fifo;
+	int cpu, rc;
+	struct kfifo_iter iter;
+	struct base_record *rcd;
+
+	for_each_possible_cpu(cpu) {
+		fifo = &per_cpu(fifos, cpu);
+		kfifo_iter_init(&iter, fifo);
+		while ((rcd = kfifo_iter_get_ptr(&iter))) {
+			if (rcd->type != RECORD_TYPE_PAD) {
+				rc = func(rcd);
+				if (rc)
+					return rc;
+			}
+			/* goto next record, the pad space is just skipped */
+			kfifo_iter_advance(&iter, rcd->len);
+		}
+	}
+
+	return 0;
+}