[bug][kernel][ipc][mutex]只有在PRIO策略下进行优先级继承 #4771
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mysterywolf
changed the title
Guozhanxin
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Jun 13, 2021
| if (thread->current_priority < mutex->owner->current_priority) | ||
| /* priority inheritance */ | ||
| if (thread->current_priority < mutex->owner->current_priority | ||
| && mutex->parent.parent.flag == RT_IPC_FLAG_PRIO) |
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如果改了这个，如果软件包或者客户代码里用fifo的方式做了互斥，也就退化成了信号量了，没有了防止优先级反转的特效，下次release版本需要强调这个API的改动了。
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优先级反转，之前指的好像不是获取同一个资源排队的问题，指的是一个线程1在获取的资源A之后再去获取资源B，其中A是以互斥量的形式获取的。因此如果此时有更高优先级的线程2来获取A，那么此时就要提高线程1的优先级，保证它不会被低优先级的打断，可以及时释放资源A。
所以我又有了疑惑，因为我们之前的文档说明“mutex具有防止优先级反转的作用”，指的应该就是这个优先级继承的机制，和其内部的排队机制应该是无关的。但是，FIFO的排队机制本身就会导致优先级被反转……
而且revert掉之前的一个pr之后，FIFO下的优先级继承本来就是假的了，没有起到防止优先级反转的作用。所以以后，mutex只有以Pro的形式创建才具有防止优先级反转的功能。。。所以FIFO在mutex里存在的意义是什么？
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刚才我计算了一下，在FIFO处理所谓“优先级反转”的问题，根本无法防止优先级反转，因为防止优先级反转的先决条件就是等待列表按照PRIO排序才可以。
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拉取/合并请求描述：(PR description)
[
FIFO策略即FCFS调度为非实时调度算法，因此无需考虑实时调度法中考虑的无界优先级反转问题。
]
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