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fix typo

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Signed-off-by: Alexander Kuleshov <kuleshovmail@gmail.com>
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Alexander Kuleshov 2018-01-11 00:14:23 +06:00
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SyncPrim/sync-1.md
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@ -24,7 +24,7 @@ mutex_unlock(&clocksource_mutex);
from the [kernel/time/clocksource.c](https://github.com/torvalds/linux/master/kernel/time/clocksource.c) source code file. This code is from the `__clocksource_register_scale` function which adds the given [clocksource](https://0xax.gitbooks.io/linux-insides/content/Timers/timers-2.html) to the clock sources list. This function produces different operations on a list with registered clock sources. For example the `clocksource_enqueue` function adds the given clock source to the list with registered clocksources - `clocksource_list`. Note that these lines of code wrapped to two functions: `mutex_lock` and `mutex_unlock` which are takes one parameter - the `clocksource_mutex` in our case. from the [kernel/time/clocksource.c](https://github.com/torvalds/linux/master/kernel/time/clocksource.c) source code file. This code is from the `__clocksource_register_scale` function which adds the given [clocksource](https://0xax.gitbooks.io/linux-insides/content/Timers/timers-2.html) to the clock sources list. This function produces different operations on a list with registered clock sources. For example the `clocksource_enqueue` function adds the given clock source to the list with registered clocksources - `clocksource_list`. Note that these lines of code wrapped to two functions: `mutex_lock` and `mutex_unlock` which are takes one parameter - the `clocksource_mutex` in our case.
These functions represents locking and unlocking based on [mutex](https://en.wikipedia.org/wiki/Mutual_exclusion) synchronization primitive. As `mutex_lock` will be executed, it allows us to prevent situation when two or more threads will execute this code while the `mute_unlock` will not be executed by process-owner of the mutex. In other words, we prevent parallel operations on a `clocksource_list`. Why do we need `mutex` here? What if two parallel processes will try to register a clock source. As we already know, the `clocksource_enqueue` function adds the given clock source to the `clocksource_list` list right after a clock source in the list which has the biggest rating (a registered clock source which has the highest frequency in the system): These functions represents locking and unlocking based on [mutex](https://en.wikipedia.org/wiki/Mutual_exclusion) synchronization primitive. As `mutex_lock` will be executed, it allows us to prevent situation when two or more threads will execute this code while the `mutex_unlock` will not be executed by process-owner of the mutex. In other words, we prevent parallel operations on a `clocksource_list`. Why do we need `mutex` here? What if two parallel processes will try to register a clock source. As we already know, the `clocksource_enqueue` function adds the given clock source to the `clocksource_list` list right after a clock source in the list which has the biggest rating (a registered clock source which has the highest frequency in the system):
```C ```C
static void clocksource_enqueue(struct clocksource *cs) static void clocksource_enqueue(struct clocksource *cs)