WarlockFish/linux-insides-zh
1
0
Fork 0
mirror of https://github.com/MintCN/linux-insides-zh.git synced 2026-04-24 18:50:42 +08:00
Code Issues Packages Projects Releases Wiki Activity

change links

Browse Source
This commit is contained in:
xinqiu
2016-06-19 21:03:23 +08:00
committed by GitHub
parent 09c489572c
commit 3fb65cd6d8
1 changed files with 8 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files

16
Timers/timers-5.md
View File

@@ -4,7 +4,7 @@ Timers and time management in the Linux kernel. Part 5.
Introduction to the `clockevents` framework
--------------------------------------------------------------------------------
This is fifth part of the [chapter](https://0xax.gitbooks.io/linux-insides/content/Timers/index.html) which describes timers and time management related stuff in the Linux kernel. As you might noted from the title of this part, the `clockevents` framework will be discussed. We already saw one framework in the [second](https://0xax.gitbooks.io/linux-insides/content/Timers/timers-2.html) part of this chapter. It was `clocksource` framework. Both of these frameworks represent timekeeping abstractions in the Linux kernel.
This is fifth part of the [chapter](https://xinqiu.gitbooks.io/linux-insides-cn/content/Timers/index.html) which describes timers and time management related stuff in the Linux kernel. As you might noted from the title of this part, the `clockevents` framework will be discussed. We already saw one framework in the [second](https://xinqiu.gitbooks.io/linux-insides-cn/content/Timers/timers-2.html) part of this chapter. It was `clocksource` framework. Both of these frameworks represent timekeeping abstractions in the Linux kernel.
At first let's refresh your memory and try to remember what is it `clocksource` framework and and what its purpose. The main goal of the `clocksource` framework is to provide `timeline`. As described in the [documentation](https://github.com/0xAX/linux/blob/master/Documentation/timers/timekeeping.txt):
@@ -130,7 +130,7 @@ The next two fields `shift` and `mult` are familiar to us. They will be used to
#define cpumask_of(cpu) (get_cpu_mask(cpu))
```
Where the `get_cpu_mask` returns the cpumask containing just a given `cpu` number. More about `cpumasks` concept you may read in the [CPU masks in the Linux kernel](https://0xax.gitbooks.io/linux-insides/content/Concepts/cpumask.html) part. In the last four lines of code we set callbacks for the clock event device suspend/resume, device shutdown and update of the clock event device state.
Where the `get_cpu_mask` returns the cpumask containing just a given `cpu` number. More about `cpumasks` concept you may read in the [CPU masks in the Linux kernel](https://xinqiu.gitbooks.io/linux-insides-cn/content/Concepts/cpumask.html) part. In the last four lines of code we set callbacks for the clock event device suspend/resume, device shutdown and update of the clock event device state.
After we finished with the initialization of the `at91sam926x` periodic timer, we can register it by the call of the following functions:
@@ -185,7 +185,7 @@ if (!dev->cpumask) {
}
```
Remember that we have set the `cpumask` of the `at91sam926x` periodic timer to first processor. If the `cpumask` field is zero, we check the number of possible processors in the system and print warning message if it is less than on. Additionally we set the `cpumask` of the given clock event device to the current processor. If you are interested in how the `smp_processor_id` macro is implemented, you can read more about it in the fourth [part](https://0xax.gitbooks.io/linux-insides/content/Initialization/linux-initialization-4.html) of the Linux kernel initialization process chapter.
Remember that we have set the `cpumask` of the `at91sam926x` periodic timer to first processor. If the `cpumask` field is zero, we check the number of possible processors in the system and print warning message if it is less than on. Additionally we set the `cpumask` of the given clock event device to the current processor. If you are interested in how the `smp_processor_id` macro is implemented, you can read more about it in the fourth [part](https://xinqiu.gitbooks.io/linux-insides-cn/content/Initialization/linux-initialization-4.html) of the Linux kernel initialization process chapter.
After this check we lock the actual code of the clock event device registration by the call following macros:
@@ -385,11 +385,11 @@ That's all.
Conclusion
-------------------------------------------------------------------------------
This is the end of the fifth part of the [chapter](https://0xax.gitbooks.io/linux-insides/content/Timers/index.html) that describes timers and timer management related stuff in the Linux kernel. In the previous part got acquainted with the `timers` concept. In this part we continued to learn time management related stuff in the Linux kernel and saw a little about yet another framework - `clockevents`.
This is the end of the fifth part of the [chapter](https://xinqiu.gitbooks.io/linux-insides-cn/content/Timers/index.html) that describes timers and timer management related stuff in the Linux kernel. In the previous part got acquainted with the `timers` concept. In this part we continued to learn time management related stuff in the Linux kernel and saw a little about yet another framework - `clockevents`.
If you have questions or suggestions, feel free to ping me in twitter [0xAX](https://twitter.com/0xAX), drop me [email](anotherworldofworld@gmail.com) or just create [issue](https://github.com/0xAX/linux-insides/issues/new).
If you have questions or suggestions, feel free to ping me in twitter [0xAX](https://twitter.com/0xAX), drop me [email](anotherworldofworld@gmail.com) or just create [issue](https://github.com/MintCN/linux-insides-zh/issues/new).
**Please note that English is not my first language and I am really sorry for any inconvenience. If you found any mistakes please send me PR to [linux-insides](https://github.com/0xAX/linux-insides).**
**Please note that English is not my first language and I am really sorry for any inconvenience. If you found any mistakes please send me PR to [linux-insides](https://github.com/MintCN/linux-insides-zh).**
Links
-------------------------------------------------------------------------------
@@ -409,7 +409,7 @@ Links
* [local APIC](https://en.wikipedia.org/wiki/Advanced_Programmable_Interrupt_Controller)
* [C3 state](https://en.wikipedia.org/wiki/Advanced_Configuration_and_Power_Interface#Device_states)
* [Periodic Interval Timer (PIT) for at91sam926x](http://www.atmel.com/Images/doc6062.pdf)
* [CPU masks in the Linux kernel](https://0xax.gitbooks.io/linux-insides/content/Concepts/cpumask.html)
* [CPU masks in the Linux kernel](https://xinqiu.gitbooks.io/linux-insides-cn/content/Concepts/cpumask.html)
* [deadlock](https://en.wikipedia.org/wiki/Deadlock)
* [CPU hotplug](https://www.kernel.org/doc/Documentation/cpu-hotplug.txt)
* [previous part](https://0xax.gitbooks.io/linux-insides/content/Timers/timers-3.html)
* [previous part](https://xinqiu.gitbooks.io/linux-insides-cn/content/Timers/timers-3.html)