经过x86测试，得知写入数据大于ringbuffer给出的最大尺寸4096后，剩余的数据虽然走kfifo_put方法，但是数据并没有写入或者覆盖掉起始处的buffer，导致数据丢失，所有后续需要针对这个问题进行判断：如果缓冲区满了就等待，当读者将数据取走腾出空间了，写者再写入。这样写线程可以让出cpu，让他在这个等待间隙做其它的事情。当然我的测试方法是写者很快，而读者很慢的情景

home-coder · home-coder · commit 40f3c07bf12f · 2017-07-02T16:00:32.000+08:00
diff --git a/Makefile b/Makefile
@@ -1,6 +1,6 @@
-ARCH=arm
+#ARCH=arm
 #与硬件相关，需要联调
-#ARCH=x86
+ARCH=x86
 #$(info, $(ARCH))//内核 androidmk使用
 ifeq ($(ARCH), arm)
     CC = ~/basic/cross_compile/gcc-4.6.2-glibc-2.13-linaro-multilib-2011.12/fsl-linaro-toolchain/bin/arm-fsl-linux-gnueabi-gcc
diff --git a/kfifo.c b/kfifo.c
@@ -57,7 +57,8 @@ unsigned int __kfifo_put(struct kfifo *fifo, unsigned char *buffer,
 	memcpy(fifo->buffer, buffer + l, len - l);
 
 	fifo->in += len;
-
+	static int i = 0;
+	printf("put put put %d\n", i++);
 	return len;
 }
 
diff --git a/test.c b/test.c
@@ -38,9 +38,10 @@ void thread_reader(void *param)
 			counter++;
 		}
 		if (counter > 20) {
-			break;
+			//break;
 		}
-		usleep(50000);
+		sleep(1);
+		//usleep(50000);
 	}
 }
 
@@ -51,19 +52,19 @@ void thread_writer(void *param)
 	unsigned char buffer[32];
 	struct ll_param *p = (struct ll_param *)param;
 
-	for (counter = 0; counter < 100; counter++) {
+	for (counter = 0; counter < 2000; counter++) {
 		bzero(buffer, 32);
 		sprintf((char *)buffer, "This is %d message.n", counter);
 		kfifo_put(p->fifo, buffer, 32);	//strlen((char *)buffer)  
-		usleep(100);
+//		usleep(100);
 	}
 }
 #else
 void thread_writer(void *param)
 {
 #define PAGE_SIZE (4*1024)
 #define PAGE_OFFSET               0xc0000000 //32位的偏移3G, 但是我在内核求得用户空间地址了，这个变量不需要了
-#define KERNEL_VIRT_ADDR 0x2249c000	//此处地址即为内核模块打印的地址p，动态的不固定，需要自行修改
+#define KERNEL_VIRT_ADDR 0x22049000	//此处地址即为内核模块打印的地址p，动态的不固定，需要自行修改
 	unsigned char *buffer;
 	int fd;
 	unsigned long phy_addr;
@@ -79,6 +80,8 @@ void thread_writer(void *param)
 		perror("mmap");
 	while (1) {
 		kfifo_put(p->fifo, buffer, 32);	//strlen((char *)buffer)  
+		bzero(buffer, 32);
+		usleep(10);
 	}
 
 	munmap(buffer, PAGE_SIZE);

Original file line number	Diff line number	Diff line change
`@@ -57,7 +57,8 @@ unsigned int __kfifo_put(struct kfifo fifo, unsigned char buffer,`
`57`	`57`	`memcpy(fifo->buffer, buffer + l, len - l);`
`58`	`58`
`59`	`59`	`fifo->in += len;`
`60`		`-`
	`60`	`+ static int i = 0;`
	`61`	`+ printf("put put put %d\n", i++);`
`61`	`62`	`return len;`
`62`	`63`	`}`
`63`	`64`
Original file line number	Diff line number	Diff line change
`@@ -38,9 +38,10 @@ void thread_reader(void *param)`
`38`	`38`	`counter++;`
`39`	`39`	`}`
`40`	`40`	`if (counter > 20) {`
`41`		`- break;`
	`41`	`+ //break;`
`42`	`42`	`}`
`43`		`- usleep(50000);`
	`43`	`+ sleep(1);`
	`44`	`+ //usleep(50000);`
`44`	`45`	`}`
`45`	`46`	`}`
`46`	`47`
`@@ -51,19 +52,19 @@ void thread_writer(void *param)`
`51`	`52`	`unsigned char buffer[32];`
`52`	`53`	`struct ll_param p = (struct ll_param )param;`
`53`	`54`
`54`		`- for (counter = 0; counter < 100; counter++) {`
	`55`	`+ for (counter = 0; counter < 2000; counter++) {`
`55`	`56`	`bzero(buffer, 32);`
`56`	`57`	`sprintf((char *)buffer, "This is %d message.n", counter);`
`57`	`58`	`kfifo_put(p->fifo, buffer, 32); //strlen((char *)buffer)`
`58`		`- usleep(100);`
	`59`	`+// usleep(100);`
`59`	`60`	`}`
`60`	`61`	`}`
`61`	`62`	`#else`
`62`	`63`	`void thread_writer(void *param)`
`63`	`64`	`{`
`64`	`65`	`#define PAGE_SIZE (4*1024)`
`65`	`66`	`#define PAGE_OFFSET 0xc0000000 //32位的偏移3G, 但是我在内核求得用户空间地址了，这个变量不需要了`
`66`		`-#define KERNEL_VIRT_ADDR 0x2249c000 //此处地址即为内核模块打印的地址p，动态的不固定，需要自行修改`
	`67`	`+#define KERNEL_VIRT_ADDR 0x22049000 //此处地址即为内核模块打印的地址p，动态的不固定，需要自行修改`
`67`	`68`	`unsigned char *buffer;`
`68`	`69`	`int fd;`
`69`	`70`	`unsigned long phy_addr;`
`@@ -79,6 +80,8 @@ void thread_writer(void *param)`
`79`	`80`	`perror("mmap");`
`80`	`81`	`while (1) {`
`81`	`82`	`kfifo_put(p->fifo, buffer, 32); //strlen((char *)buffer)`
	`83`	`+ bzero(buffer, 32);`
	`84`	`+ usleep(10);`
`82`	`85`	`}`
`83`	`86`
`84`	`87`	`munmap(buffer, PAGE_SIZE);`