16、 per-CPU变量
get_cpu_var();
put_cpu_var();
void *alloc_percpu(type);
void free_percpu(const void *);
per_cpu_ptr(void *ptr, int cpu)
get_cpu_ptr(ptr)
put_cpu_ptr(ptr)
老版本使用
DEFINE_PER_CPU(type, name);
EXPORT_PER_CPU_SYMBOL(name);
EXPORT_PER_CPU_SYMBOL_GPL(name);
DECLARE_PER_CPU(type, name);
DEFINE_PER_CPU(int, mypcint);
2.6内核采用了可剥夺得调度方式这些宏都不安全。
17、 内核时间变化
1、现在的各个平台的HZ为
Alpha: 1024/1200; ARM: 100/128/200/1000; CRIS: 100; i386: 1000; IA-64:
1024; M68K: 100; M68K-nommu: 50-1000; MIPS: 100/128/1000; MIPS64: 100;
PA-RISC: 100/1000; PowerPC32: 100; PowerPC64: 1000; S/390: 100; SPARC32:
100; SPARC64: 100; SuperH: 100/1000; UML: 100; v850: 24-100; x86-64: 1000.
2、由于HZ的变化，原来的jiffies计数器很快就溢出了，引入了新的计数器jiffies_64
3、#include <linux/jiffies.h>
u64 my_time = get_jiffies_64();
4、新的时间结构增加了纳秒成员变量
struct timespec current_kernel_time(void);
5、他的timer函数没变，新增
void add_timer_on(struct timer_list *timer, int cpu);
6、新增纳秒级延时函数
ndelay()；
7、POSIX clocks 参考kernel/posix-timers.c
18、 工作队列（workqueue）
1、任务队列（task queue ）接口函数都被取消，新增了workqueue接口函数
struct workqueue_struct *create_workqueue(const char *name);
DECLARE_WORK(name, void (*function)(void *), void *data);
INIT_WORK(struct work_struct *work,
void (*function)(void *), void *data);
PREPARE_WORK(struct work_struct *work,
void (*function)(void *), void *data);
2、申明struct work_struct结构
int queue_work(struct workqueue_struct *queue,
struct work_struct *work);
int queue_delayed_work(struct workqueue_struct *queue,
struct work_struct *work,
unsigned long delay);
int cancel_delayed_work(struct work_struct *work);
void flush_workqueue(struct workqueue_struct *queue);
void destroy_workqueue(struct workqueue_struct *queue);
int schedule_work(struct work_struct *work);
int schedule_delayed_work(struct work_struct *work, unsigned long
delay);
19、 新增创建VFS的"libfs"
libfs给创建一个新的文件系统提供了大量的API.
主要是对struct file_system_type的实现。
参考源代码：
drivers/hotplug/pci_hotplug_core.c
drivers/usb/core/inode.c
drivers/oprofile/oprofilefs.c
fs/ramfs/inode.c
fs/nfsd/nfsctl.c (simple_fill_super() example)
20、 DMA的变化
未变化的有：
void *pci_alloc_consistent(struct pci_dev *dev, size_t size,
dma_addr_t *dma_handle);
void pci_free_consistent(struct pci_dev *dev, size_t size,
void *cpu_addr, dma_addr_t dma_handle);
变化的有：
1、 void *dma_alloc_coherent(struct device *dev, size_t size,
dma_addr_t *dma_handle, int flag);
void dma_free_coherent(struct device *dev, size_t size,
void *cpu_addr, dma_addr_t dma_handle);
2、列举了映射方向：
enum dma_data_direction {
DMA_BIDIRECTIONAL = 0,
DMA_TO_DEVICE = 1,
DMA_FROM_DEVICE = 2,
DMA_NONE = 3,
};
3、单映射
dma_addr_t dma_map_single(struct device *dev, void *addr,
size_t size,
enum dma_data_direction direction);
void dma_unmap_single(struct device *dev, dma_addr_t dma_addr,
size_t size,
enum dma_data_direction direction);
4、页面映射
dma_addr_t dma_map_page(struct device *dev, struct page *page,
unsigned long offset, size_t size,
enum dma_data_direction direction);
void dma_unmap_page(struct device *dev, dma_addr_t dma_addr,
size_t size,
enum dma_data_direction direction);
5、有关scatter/gather的函数：
int dma_map_sg(struct device *dev, struct scatterlist *sg,
int nents, enum dma_data_direction direction);
void dma_unmap_sg(struct device *dev, struct scatterlist *sg,
int nhwentries, enum dma_data_direction direction);
6、非一致性映射（Noncoherent DMA mappings）
void *dma_alloc_noncoherent(struct device *dev, size_t size,
dma_addr_t *dma_handle, int flag);
void dma_sync_single_range(struct device *dev, dma_addr_t dma_handle,
unsigned long offset, size_t size,
enum dma_data_direction direction);
void dma_free_noncoherent(struct device *dev, size_t size,
void *cpu_addr, dma_addr_t dma_handle);
7、DAC (double address cycle)
int pci_dac_set_dma_mask(struct pci_dev *dev, u64 mask);
void pci_dac_dma_sync_single(struct pci_dev *dev,
dma64_addr_t dma_addr,
size_t len, int direction);
21、 互斥
新增seqlock主要用于：
1、少量的数据保护
2、数据比较简单(没有指针)，并且使用频率很高
3、对不产生任何副作用的数据的访问
4、访问时写者不被饿死
<linux/seqlock.h>
初始化
seqlock_t lock1 = SEQLOCK_UNLOCKED;
或seqlock_t lock2; seqlock_init(&lock2);
void write_seqlock(seqlock_t *sl);
void write_sequnlock(seqlock_t *sl);
int write_tryseqlock(seqlock_t *sl);
void write_seqlock_irqsave(seqlock_t *sl, long flags);
void write_sequnlock_irqrestore(seqlock_t *sl, long flags);
void write_seqlock_irq(seqlock_t *sl);
void write_sequnlock_irq(seqlock_t *sl);
void write_seqlock_bh(seqlock_t *sl);
void write_sequnlock_bh(seqlock_t *sl);
unsigned int read_seqbegin(seqlock_t *sl);
int read_seqretry(seqlock_t *sl, unsigned int iv);
unsigned int read_seqbegin_irqsave(seqlock_t *sl, long flags);
int read_seqretry_irqrestore(seqlock_t *sl, unsigned int iv, long
flags);
22、 内核可剥夺
<linux/preempt.h>
preempt_disable()；
preempt_enable_no_resched()；
preempt_enable_noresched()；
preempt_check_resched()；
23、 眠和唤醒
1、原来的函数可用，新增下列函数：
prepare_to_wait_exclusive()；
prepare_to_wait()；
2、等待队列的变化
typedef int (*wait_queue_func_t)(wait_queue_t *wait,
unsigned mode, int sync);
void init_waitqueue_func_entry(wait_queue_t *queue,
wait_queue_func_t func);
24、 新增完成事件（completion events）
<linux/completion.h>
init_completion(&my_comp);
void wait_for_completion(struct completion *comp);
void complete(struct completion *comp);
void complete_all(struct completion *comp);
25、 RCU（Read-copy-update）
rcu_read_lock();
void call_rcu(struct rcu_head *head, void (*func)(void *arg),
void *arg);