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是否应该使用非递归锁 #38

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yvxiang opened this issue Jun 18, 2015 · 3 comments
Closed

是否应该使用非递归锁 #38

yvxiang opened this issue Jun 18, 2015 · 3 comments

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@yvxiang
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yvxiang commented Jun 18, 2015

commit 1e0d8ad让我想起了一个问题，当前mutex.h中的Mutex类在初始化pthread_mutex_t变量时，没有指定pthread_mutexattr_t属性，这将导致该互斥量的属性为PTHREAD_MUTEX_DEFAULT。而在linux下，这种属性的互斥量在 没有解锁时又重新加锁 下的行为是未定义的。是否有必要将互斥量改为非递归的？感觉这样会安全些。
@yvxiang yvxiang closed this as completed Jun 18, 2015
@bluebore
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linux下，重复加锁是会死锁的，所以当前实现是可以工作的，我会再研究下其他几种类型，看哪个更适合替换。
关闭issue的原因是什么，你又有新的发现？

@yvxiang
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yvxiang commented Jun 18, 2015

上午看错了，以为当前代码中有重复加锁的地方，但是居然没有死锁，现在排查清楚了，是看错了锁……

POSIX标准的手册中写的在PTHREAD_MUTEX_DEFAULT情况下，重复加锁会导致不确定行为，linux的一些版本中，PTHREAD_MUTEX_DEFAULT被映射到了PTHREAD_MUTEX_NORMAL，这样便会导致死锁。但这种映射是没有保证的。所以我感觉还是有必要替换一下的，至少应该改为PTHREAD_MUTEX_NORMAL。

@yvxiang yvxiang reopened this Jun 18, 2015
@bluebore
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bluebore commented Feb 5, 2016

已经移到baidu/common中了

@bluebore bluebore closed this as completed Feb 5, 2016
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