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development-guidelines-37.md 12.55 KB

# Development Guidelines<a name="EN-US_TOPIC_0311018431"></a>

## Usage Scenarios<a name="en-us_topic_0175921104_section10746131142833"></a>

A spinlock provides a mutual exclusion mechanism to prevent two tasks from accessing the same shared resource at the same time.

## Functions<a name="en-us_topic_0175921104_section335816715456"></a>

The spinlock module of Huawei LiteOS provides the following functions. For details about the APIs, see the API reference.

<a name="en-us_topic_0175921104_table14234001162410"></a>
<table><thead align="left"><tr id="en-us_topic_0175921104_row20709259162410"><th class="cellrowborder" valign="top" width="30.05300530053005%" id="mcps1.1.4.1.1"><p id="en-us_topic_0175921104_p66837260162410"><a name="en-us_topic_0175921104_p66837260162410"></a><a name="en-us_topic_0175921104_p66837260162410"></a>Function Category</p>
</th>
<th class="cellrowborder" valign="top" width="23.77237723772377%" id="mcps1.1.4.1.2"><p id="en-us_topic_0175921104_p45109011162410"><a name="en-us_topic_0175921104_p45109011162410"></a><a name="en-us_topic_0175921104_p45109011162410"></a>API</p>
</th>
<th class="cellrowborder" valign="top" width="46.17461746174617%" id="mcps1.1.4.1.3"><p id="en-us_topic_0175921104_p29951237162410"><a name="en-us_topic_0175921104_p29951237162410"></a><a name="en-us_topic_0175921104_p29951237162410"></a>Description</p>
</th>
</tr>
</thead>
<tbody><tr id="en-us_topic_0175921104_row10131148162410"><td class="cellrowborder" rowspan="2" valign="top" width="30.05300530053005%" headers="mcps1.1.4.1.1 "><p id="en-us_topic_0175921104_p15316688162410"><a name="en-us_topic_0175921104_p15316688162410"></a><a name="en-us_topic_0175921104_p15316688162410"></a>Spinlock initialization</p>
</td>
<td class="cellrowborder" valign="top" width="23.77237723772377%" headers="mcps1.1.4.1.2 "><p id="en-us_topic_0175921104_p32692216162410"><a name="en-us_topic_0175921104_p32692216162410"></a><a name="en-us_topic_0175921104_p32692216162410"></a>LOS_SpinInit</p>
</td>
<td class="cellrowborder" valign="top" width="46.17461746174617%" headers="mcps1.1.4.1.3 "><p id="en-us_topic_0175921104_p30823853162410"><a name="en-us_topic_0175921104_p30823853162410"></a><a name="en-us_topic_0175921104_p30823853162410"></a>Dynamically initializes a spinlock.</p>
</td>
</tr>
<tr id="en-us_topic_0175921104_row185813332337"><td class="cellrowborder" valign="top" headers="mcps1.1.4.1.1 "><p id="en-us_topic_0175921104_p9582173353317"><a name="en-us_topic_0175921104_p9582173353317"></a><a name="en-us_topic_0175921104_p9582173353317"></a>SPIN_LOCK_INIT</p>
</td>
<td class="cellrowborder" valign="top" headers="mcps1.1.4.1.2 "><p id="en-us_topic_0175921104_p15582103317339"><a name="en-us_topic_0175921104_p15582103317339"></a><a name="en-us_topic_0175921104_p15582103317339"></a>Statically initializes a spinlock.</p>
</td>
</tr>
<tr id="en-us_topic_0175921104_row54162342162410"><td class="cellrowborder" rowspan="3" valign="top" width="30.05300530053005%" headers="mcps1.1.4.1.1 "><p id="en-us_topic_0175921104_p25073564162410"><a name="en-us_topic_0175921104_p25073564162410"></a><a name="en-us_topic_0175921104_p25073564162410"></a>Spinlock request and release</p>
</td>
<td class="cellrowborder" valign="top" width="23.77237723772377%" headers="mcps1.1.4.1.2 "><p id="en-us_topic_0175921104_p17692840162410"><a name="en-us_topic_0175921104_p17692840162410"></a><a name="en-us_topic_0175921104_p17692840162410"></a>LOS_SpinLock</p>
</td>
<td class="cellrowborder" valign="top" width="46.17461746174617%" headers="mcps1.1.4.1.3 "><p id="en-us_topic_0175921104_p23833903162410"><a name="en-us_topic_0175921104_p23833903162410"></a><a name="en-us_topic_0175921104_p23833903162410"></a>Requests a specified spinlock. If the spinlock cannot be obtained, the system waits in a loop.</p>
</td>
</tr>
<tr id="en-us_topic_0175921104_row6130742123610"><td class="cellrowborder" valign="top" headers="mcps1.1.4.1.1 "><p id="en-us_topic_0175921104_p41301442183610"><a name="en-us_topic_0175921104_p41301442183610"></a><a name="en-us_topic_0175921104_p41301442183610"></a>LOS_SpinTrylock</p>
</td>
<td class="cellrowborder" valign="top" headers="mcps1.1.4.1.2 "><p id="en-us_topic_0175921104_p16130442103610"><a name="en-us_topic_0175921104_p16130442103610"></a><a name="en-us_topic_0175921104_p16130442103610"></a>Attempts to request a specified spinlock. If the spinlock cannot be obtained, a failure message is returned, and the system does not wait in a loop.</p>
</td>
</tr>
<tr id="en-us_topic_0175921104_row13178541162410"><td class="cellrowborder" valign="top" headers="mcps1.1.4.1.1 "><p id="en-us_topic_0175921104_p60828923162410"><a name="en-us_topic_0175921104_p60828923162410"></a><a name="en-us_topic_0175921104_p60828923162410"></a>LOS_SpinUnlock</p>
</td>
<td class="cellrowborder" valign="top" headers="mcps1.1.4.1.2 "><p id="en-us_topic_0175921104_p28195705162410"><a name="en-us_topic_0175921104_p28195705162410"></a><a name="en-us_topic_0175921104_p28195705162410"></a>Releases a spinlock.</p>
</td>
</tr>
<tr id="en-us_topic_0175921104_row829833285118"><td class="cellrowborder" rowspan="2" valign="top" width="30.05300530053005%" headers="mcps1.1.4.1.1 "><p id="en-us_topic_0175921104_p1826134717516"><a name="en-us_topic_0175921104_p1826134717516"></a><a name="en-us_topic_0175921104_p1826134717516"></a>Spinlock request and release (with disabled interrupt)</p>
</td>
<td class="cellrowborder" valign="top" width="23.77237723772377%" headers="mcps1.1.4.1.2 "><p id="en-us_topic_0175921104_p6298132165119"><a name="en-us_topic_0175921104_p6298132165119"></a><a name="en-us_topic_0175921104_p6298132165119"></a>LOS_SpinLockSave</p>
</td>
<td class="cellrowborder" valign="top" width="46.17461746174617%" headers="mcps1.1.4.1.3 "><p id="en-us_topic_0175921104_p329873275110"><a name="en-us_topic_0175921104_p329873275110"></a><a name="en-us_topic_0175921104_p329873275110"></a>Requests a spinlock after the interrupt is disabled.</p>
</td>
</tr>
<tr id="en-us_topic_0175921104_row2474173655120"><td class="cellrowborder" valign="top" headers="mcps1.1.4.1.1 "><p id="en-us_topic_0175921104_p3474123617518"><a name="en-us_topic_0175921104_p3474123617518"></a><a name="en-us_topic_0175921104_p3474123617518"></a>LOS_SpinUnlockRestore</p>
</td>
<td class="cellrowborder" valign="top" headers="mcps1.1.4.1.2 "><p id="en-us_topic_0175921104_p1347433685113"><a name="en-us_topic_0175921104_p1347433685113"></a><a name="en-us_topic_0175921104_p1347433685113"></a>Releases a spinlock and restores the interrupt.</p>
</td>
</tr>
<tr id="en-us_topic_0175921104_row13315131215318"><td class="cellrowborder" valign="top" width="30.05300530053005%" headers="mcps1.1.4.1.1 "><p id="en-us_topic_0175921104_p0315812115318"><a name="en-us_topic_0175921104_p0315812115318"></a><a name="en-us_topic_0175921104_p0315812115318"></a>Spinlock holding status</p>
</td>
<td class="cellrowborder" valign="top" width="23.77237723772377%" headers="mcps1.1.4.1.2 "><p id="en-us_topic_0175921104_p133153129534"><a name="en-us_topic_0175921104_p133153129534"></a><a name="en-us_topic_0175921104_p133153129534"></a>LOS_SpinHeld</p>
</td>
<td class="cellrowborder" valign="top" width="46.17461746174617%" headers="mcps1.1.4.1.3 "><p id="en-us_topic_0175921104_p123154125539"><a name="en-us_topic_0175921104_p123154125539"></a><a name="en-us_topic_0175921104_p123154125539"></a>Checks whether a spinlock is held.</p>
</td>
</tr>
</tbody>
</table>

## Development Process<a name="en-us_topic_0175921104_section1137085411376"></a>

The typical spinlock development process is as follows:

1.  Spinlocks depend on the SMP. Run the  **make menuconfig**  command and choose  **Kernel**  \>  **Enable Kernel SMP**  to configure the spinlock.

<a name="en-us_topic_0175921104_table34659900162615"></a>
    <table><thead align="left"><tr id="en-us_topic_0175921104_row3414390162615"><th class="cellrowborder" valign="top" width="21.3978602139786%" id="mcps1.1.6.1.1"><p id="en-us_topic_0175921104_p8130151162615"><a name="en-us_topic_0175921104_p8130151162615"></a><a name="en-us_topic_0175921104_p8130151162615"></a>Configuration Item</p>
    </th>
    <th class="cellrowborder" valign="top" width="35.35646435356465%" id="mcps1.1.6.1.2"><p id="en-us_topic_0175921104_p54562526162615"><a name="en-us_topic_0175921104_p54562526162615"></a><a name="en-us_topic_0175921104_p54562526162615"></a>Description</p>
    </th>
    <th class="cellrowborder" valign="top" width="15.608439156084392%" id="mcps1.1.6.1.3"><p id="en-us_topic_0175921104_p57488448162615"><a name="en-us_topic_0175921104_p57488448162615"></a><a name="en-us_topic_0175921104_p57488448162615"></a>Value Range</p>
    </th>
    <th class="cellrowborder" valign="top" width="12.768723127687231%" id="mcps1.1.6.1.4"><p id="en-us_topic_0175921104_p26052727162615"><a name="en-us_topic_0175921104_p26052727162615"></a><a name="en-us_topic_0175921104_p26052727162615"></a>Default Value</p>
    </th>
    <th class="cellrowborder" valign="top" width="14.86851314868513%" id="mcps1.1.6.1.5"><p id="en-us_topic_0175921104_p29896171162615"><a name="en-us_topic_0175921104_p29896171162615"></a><a name="en-us_topic_0175921104_p29896171162615"></a>Dependency</p>
    </th>
    </tr>
    </thead>
    <tbody><tr id="en-us_topic_0175921104_row5670787162615"><td class="cellrowborder" valign="top" width="21.3978602139786%" headers="mcps1.1.6.1.1 "><p id="en-us_topic_0175921104_p767075542311"><a name="en-us_topic_0175921104_p767075542311"></a><a name="en-us_topic_0175921104_p767075542311"></a>LOSCFG_KERNEL_SMP</p>
    </td>
    <td class="cellrowborder" valign="top" width="35.35646435356465%" headers="mcps1.1.6.1.2 "><p id="en-us_topic_0175921104_p27727169162615"><a name="en-us_topic_0175921104_p27727169162615"></a><a name="en-us_topic_0175921104_p27727169162615"></a>Whether to enable the SMP.</p>
    </td>
    <td class="cellrowborder" valign="top" width="15.608439156084392%" headers="mcps1.1.6.1.3 "><p id="en-us_topic_0175921104_p31308215162615"><a name="en-us_topic_0175921104_p31308215162615"></a><a name="en-us_topic_0175921104_p31308215162615"></a>YES/NO</p>
    </td>
    <td class="cellrowborder" valign="top" width="12.768723127687231%" headers="mcps1.1.6.1.4 "><p id="en-us_topic_0175921104_p52937457162615"><a name="en-us_topic_0175921104_p52937457162615"></a><a name="en-us_topic_0175921104_p52937457162615"></a>YES</p>
    </td>
    <td class="cellrowborder" valign="top" width="14.86851314868513%" headers="mcps1.1.6.1.5 "><p id="en-us_topic_0175921104_p60075607162615"><a name="en-us_topic_0175921104_p60075607162615"></a><a name="en-us_topic_0175921104_p60075607162615"></a>Multi-core hardware is supported.</p>
    </td>
    </tr>
    <tr id="en-us_topic_0175921104_row3809559162615"><td class="cellrowborder" valign="top" width="21.3978602139786%" headers="mcps1.1.6.1.1 "><p id="en-us_topic_0175921104_p131131669249"><a name="en-us_topic_0175921104_p131131669249"></a><a name="en-us_topic_0175921104_p131131669249"></a>LOSCFG_KERNEL_SMP_CORE_NUM</p>
    </td>
    <td class="cellrowborder" valign="top" width="35.35646435356465%" headers="mcps1.1.6.1.2 "><p id="en-us_topic_0175921104_p30022176162615"><a name="en-us_topic_0175921104_p30022176162615"></a><a name="en-us_topic_0175921104_p30022176162615"></a>Number of cores in the multi-core scenario.</p>
    </td>
    <td class="cellrowborder" valign="top" width="15.608439156084392%" headers="mcps1.1.6.1.3 "><p id="en-us_topic_0175921104_p15877214162615"><a name="en-us_topic_0175921104_p15877214162615"></a><a name="en-us_topic_0175921104_p15877214162615"></a>Depends on the architecture.</p>
    </td>
    <td class="cellrowborder" valign="top" width="12.768723127687231%" headers="mcps1.1.6.1.4 "><p id="en-us_topic_0175921104_p10985932162615"><a name="en-us_topic_0175921104_p10985932162615"></a><a name="en-us_topic_0175921104_p10985932162615"></a>2</p>
    </td>
    <td class="cellrowborder" valign="top" width="14.86851314868513%" headers="mcps1.1.6.1.5 "><p id="en-us_topic_0175921104_p17445266162615"><a name="en-us_topic_0175921104_p17445266162615"></a><a name="en-us_topic_0175921104_p17445266162615"></a>None</p>
    </td>
    </tr>
    </tbody>
    </table>

2.  To create a spinlock, call the LOS\_SpinInit API to initialize the spinlock, or call SPIN\_LOCK\_INIT API to initialize the spinlock of the static memory.
3.  Call the LOS\_SpinLock, LOS\_SpinTrylock, or LOS\_SpinLockSave API to request a spinlock. If the request is successful, the code for lock protection is executed. If the request fails, the system enters a busy loop till a spinlock is obtained.
4.  Call the LOS\_SpinUnlock/LOS\_SpinUnlockRestore API to release a spinlock. After the lock protection code is executed, the corresponding spinlock is released, so that other cores can request the spinlock.

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提交于 2021-03-21 22:31 . update porting guide and add the english documents.

Development Guidelines

Usage Scenarios

A spinlock provides a mutual exclusion mechanism to prevent two tasks from accessing the same shared resource at the same time.

Functions

The spinlock module of Huawei LiteOS provides the following functions. For details about the APIs, see the API reference.

Function Category	API	Description
Spinlock initialization	LOS_SpinInit	Dynamically initializes a spinlock.
Spinlock initialization	SPIN_LOCK_INIT	Statically initializes a spinlock.
Spinlock request and release	LOS_SpinLock	Requests a specified spinlock. If the spinlock cannot be obtained, the system waits in a loop.
	LOS_SpinTrylock	Attempts to request a specified spinlock. If the spinlock cannot be obtained, a failure message is returned, and the system does not wait in a loop.
	LOS_SpinUnlock	Releases a spinlock.
Spinlock request and release (with disabled interrupt)	LOS_SpinLockSave	Requests a spinlock after the interrupt is disabled.
Spinlock request and release (with disabled interrupt)	LOS_SpinUnlockRestore	Releases a spinlock and restores the interrupt.
Spinlock holding status	LOS_SpinHeld	Checks whether a spinlock is held.

Development Process

The typical spinlock development process is as follows:

Spinlocks depend on the SMP. Run the make menuconfig command and choose Kernel > Enable Kernel SMP to configure the spinlock.

Configuration Item	Description	Value Range	Default Value	Dependency
LOSCFG_KERNEL_SMP	Whether to enable the SMP.	YES/NO	YES	Multi-core hardware is supported.
LOSCFG_KERNEL_SMP_CORE_NUM	Number of cores in the multi-core scenario.	Depends on the architecture.	2	None

To create a spinlock, call the LOS_SpinInit API to initialize the spinlock, or call SPIN_LOCK_INIT API to initialize the spinlock of the static memory.
Call the LOS_SpinLock, LOS_SpinTrylock, or LOS_SpinLockSave API to request a spinlock. If the request is successful, the code for lock protection is executed. If the request fails, the system enters a busy loop till a spinlock is obtained.
Call the LOS_SpinUnlock/LOS_SpinUnlockRestore API to release a spinlock. After the lock protection code is executed, the corresponding spinlock is released, so that other cores can request the spinlock.

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