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SyncPrim: Fix wrong link to kernel files

A few links to kernel files in Torvalds's github mirror repo is missing
'/blob/'.  This commit fixes the links.

Signed-off-by: SeongJae Park <sj38.park@gmail.com>
pull/672/head
SeongJae Park 4 months ago
parent
commit
eb1bd311bb
1 changed files with 6 additions and 6 deletions
  1. 6
    6
      SyncPrim/linux-sync-1.md

+ 6
- 6
SyncPrim/linux-sync-1.md View File

@@ -22,7 +22,7 @@ clocksource_select();
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/linux-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 takes one parameter - the `clocksource_mutex` in our case.
from the [kernel/time/clocksource.c](https://github.com/torvalds/linux/blob/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/linux-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 takes one parameter - the `clocksource_mutex` in our case.

These functions represent 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 the 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):

@@ -79,7 +79,7 @@ typedef struct spinlock {
} spinlock_t;
```

and located in the [include/linux/spinlock_types.h](https://github.com/torvalds/linux/master/include/linux/spinlock_types.h) header file. We may see that its implementation depends on the state of the `CONFIG_DEBUG_LOCK_ALLOC` kernel configuration option. We will skip this now, because all debugging related stuff will be in the end of this part. So, if the `CONFIG_DEBUG_LOCK_ALLOC` kernel configuration option is disabled, the `spinlock_t` contains [union](https://en.wikipedia.org/wiki/Union_type#C.2FC.2B.2B) with one field which is - `raw_spinlock`:
and located in the [include/linux/spinlock_types.h](https://github.com/torvalds/linux/blob/master/include/linux/spinlock_types.h) header file. We may see that its implementation depends on the state of the `CONFIG_DEBUG_LOCK_ALLOC` kernel configuration option. We will skip this now, because all debugging related stuff will be in the end of this part. So, if the `CONFIG_DEBUG_LOCK_ALLOC` kernel configuration option is disabled, the `spinlock_t` contains [union](https://en.wikipedia.org/wiki/Union_type#C.2FC.2B.2B) with one field which is - `raw_spinlock`:

```C
typedef struct spinlock {
@@ -89,7 +89,7 @@ typedef struct spinlock {
} spinlock_t;
```

The `raw_spinlock` structure defined in the [same](https://github.com/torvalds/linux/master/include/linux/spinlock_types.h) header file represents the implementation of `normal` spinlock. Let's look how the `raw_spinlock` structure is defined:
The `raw_spinlock` structure defined in the [same](https://github.com/torvalds/linux/blob/master/include/linux/spinlock_types.h) header file represents the implementation of `normal` spinlock. Let's look how the `raw_spinlock` structure is defined:

```C
typedef struct raw_spinlock {
@@ -104,7 +104,7 @@ typedef struct raw_spinlock {
} raw_spinlock_t;
```

where the `arch_spinlock_t` represents architecture-specific `spinlock` implementation. As we mentioned above, we will skip debugging kernel configuration options. As we focus on [x86_64](https://en.wikipedia.org/wiki/X86-64) architecture in this book, the `arch_spinlock_t` that we will consider is defined in the [include/asm-generic/qspinlock_types.h](https://github.com/torvalds/linux/master/include/asm-generic/qspinlock_types.h) header file and looks:
where the `arch_spinlock_t` represents architecture-specific `spinlock` implementation. As we mentioned above, we will skip debugging kernel configuration options. As we focus on [x86_64](https://en.wikipedia.org/wiki/X86-64) architecture in this book, the `arch_spinlock_t` that we will consider is defined in the [include/asm-generic/qspinlock_types.h](https://github.com/torvalds/linux/blob/master/include/asm-generic/qspinlock_types.h) header file and looks:

```C
typedef struct qspinlock {
@@ -133,7 +133,7 @@ We will not stop on this structures for now. Let's look at the operations on a `
* `spin_is_locked` - returns the state of the given `spinlock`;
* and etc.

Let's look on the implementation of the `spin_lock_init` macro. As I already wrote, this and other macro are defined in the [include/linux/spinlock.h](https://github.com/torvalds/linux/master/include/linux/spinlock.h) header file and the `spin_lock_init` macro looks:
Let's look on the implementation of the `spin_lock_init` macro. As I already wrote, this and other macro are defined in the [include/linux/spinlock.h](https://github.com/torvalds/linux/blob/master/include/linux/spinlock.h) header file and the `spin_lock_init` macro looks:

```C
#define spin_lock_init(_lock) \
@@ -161,7 +161,7 @@ do { \
} while (0) \
```

assigns the value of the `__RAW_SPIN_LOCK_UNLOCKED` with the given `spinlock` to the given `raw_spinlock_t`. As we may understand from the name of the `__RAW_SPIN_LOCK_UNLOCKED` macro, this macro does initialization of the given `spinlock` and set it to `released` state. This macro is defined in the [include/linux/spinlock_types.h](https://github.com/torvalds/linux/master/include/linux/spinlock_types.h) header file and expands to the following macros:
assigns the value of the `__RAW_SPIN_LOCK_UNLOCKED` with the given `spinlock` to the given `raw_spinlock_t`. As we may understand from the name of the `__RAW_SPIN_LOCK_UNLOCKED` macro, this macro does initialization of the given `spinlock` and set it to `released` state. This macro is defined in the [include/linux/spinlock_types.h](https://github.com/torvalds/linux/blob/master/include/linux/spinlock_types.h) header file and expands to the following macros:

```C
#define __RAW_SPIN_LOCK_UNLOCKED(lockname) \

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