Follow Excellent, Success will Chase you

0%

IPI通信(SMP)

IPI(Interrupt-Procecesorr Interrupt): 处理中间的中断

主要应用是一个处理器让另一个处理器做特定的事情(function和sched)

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
              +---------------------------+-+
system boot | request_percpu_irq() +
| mailbox irq handle +
+--+-----------------------+--+
| |
| |
+--v--+ +---v-+
| CPU0| > CPU1|
+--+--+ +----++
| |
+----+----+ +-----+-----+
|mailbox0 | +-->mailbox1 |
+---------+ | +-----------+
|
+---------------+ |
system run A send IPI CPU1 |
write mailbox1 |
| |
| +-----v-----------------+---+
+------+----+ | 1. 读取mailbox中的action +
| Task A | | 2. 通过action判断IPI类型 +
| | | 3. 进行function和sched处理+
+-----------+ | +
+---------------------------+

在多核处理器中,每一个CPU核有一个mailbox(相当于邮箱),如果需要进行IPI通信时,其主要通过IPI的中断实现。假设CPU0需要给CPU1发送一个action(actionI的类型:SMP_CALL_FUNCTION,SMP_RESCHEDULE_YOURSELF等)时, 只需要CPU0向CPU1的mailbox中写于action的id(相当于信),此时CPU1将产生一个IPI中断(表明收到信),mailbox的中断处理程序将读取mailbox(相当于看信)中的action,判断action的类型进行相应的处理。

MIPS架构下的IPI通信

  1. 关闭中断后还会发送IPI

MIPS接口

1
2
3
4
5
struct plat_smp_ops {
void (*send_ipi_single)(int cpu, unsigned int action);
void (*send_ipi_mask)(const struct cpumask *mask, unsigned int action);
...
}

IPI通信就是多个处理器之间的交流
send_ipi_single: 一对一聊天
send_ipi_mask : 群发,mask表示群发的成员(CPU)

action类型

1
2
3
4
5
6
7
#define SMP_RESCHEDULE_YOURSELF 0x1 /* XXX braindead */
#define SMP_CALL_FUNCTION 0x2
/* Octeon - Tell another core to flush its icache */
#define SMP_ICACHE_FLUSH 0x4
/* Used by kexec crashdump to save all cpu's state */
#define SMP_DUMP 0x8
#define SMP_IPI_TIMER 0xC

file: arch/mips/include/asm/smp.h

  1. 不同的action(活动)何时将产生?
  2. 各自都有什么作用?

SMP_RESCHEDULE_YOURSELF

SMP_RESCHEDULE_YOURSELF将直接调用scheduler_ipi.将任务插入目标CPU的运行队列。

1
2
3
4
5
6
7
8
9
10
11
/*
* this function sends a 'reschedule' IPI to another CPU.
* it goes straight through and wastes no time serializing
* anything. Worst case is that we lose a reschedule ...
*/
static inline void smp_send_reschedule(int cpu)
{
extern struct plat_smp_ops *mp_ops; /* private */

mp_ops->send_ipi_single(cpu, SMP_RESCHEDULE_YOURSELF);
}

file: arch/mips/include/asm/smp.h

SMP_CALL_FUNCTION

SMP_CALL_FUNCTION:将特定的函数在目标CPU上运行

  • 内核回调接口:
    1
    2
    3
    4
    5
    6
    7
    8
    9
    10
    11
    12
    13
    static inline void arch_send_call_function_single_ipi(int cpu)
    {
    extern struct plat_smp_ops *mp_ops; /* private */

    mp_ops->send_ipi_mask(&cpumask_of_cpu(cpu), SMP_CALL_FUNCTION);
    }

    static inline void arch_send_call_function_ipi_mask(const struct cpumask *mask)
    {
    extern struct plat_smp_ops *mp_ops; /* private */

    mp_ops->send_ipi_mask(mask, SMP_CALL_FUNCTION);
    }

file: arch/mips/include/asm/smp.h

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
/*
* smp_call_function_single - Run a function on a specific CPU
* @func: The function to run. This must be fast and non-blocking.
* @info: An arbitrary pointer to pass to the function.
* @wait: If true, wait until function has completed on other CPUs.
*
* Returns 0 on success, else a negative status code.
*/

smp_call_function_single
\->generic_exec_single
\->arch_send_call_function_single_ipi

/**
* smp_call_function_many(): Run a function on a set of other CPUs.
* @mask: The set of cpus to run on (only runs on online subset).
* @func: The function to run. This must be fast and non-blocking.
* @info: An arbitrary pointer to pass to the function.
* @wait: If true, wait (atomically) until function has completed
* on other CPUs.
*
* If @wait is true, then returns once @func has returned.
*
* You must not call this function with disabled interrupts or from a
* hardware interrupt handler or from a bottom half handler. Preemption
* must be disabled when calling this function.
*/

smp_call_function_many
\->arch_send_call_function_ipi_mask

file: kernel/smp.c

刷新TLB

多核进行TLB的同步?

-------------本文结束感谢您的阅读-------------
  • 本文作者: Winddoing
  • 本文链接: https://winddoing.github.io/post/60164.html
  • 作者声明: 本博文为个人笔记, 由于个人能力有限,难免出现错误,欢迎大家批评指正。
  • 版权声明: 本博客所有文章除特别声明外,均采用 BY-NC-SA 许可协议。转载请注明出处!