Fix deadlock in MemoryPool #10400
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Fix deadlock in MemoryPool #10400
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`MemoryPool::poolMutex_` is used to protect `MemoryPool::children_` in
the following 4 member methods:
`addLeafChild()`/`addAggregateChild()`/`getChildCount()`/`visitChildren`.
In other words, to avoid deadlock:
1. First of all, we can't call the above 4 methods while holding
`poolMutex_`.
2. Furthermore, we cannot call methods that use these 4 methods while
holding `poolMutex_`;
3. Finally, **there cannot be any direct or indirect calls between
these 4 methods. (This is the root cause of this problem)**.
```cpp
addAggregateChild() ------ will acquire 'poolMutex_'
--> toString() [When duplicate names appear, used to print error messages]
--> usedBytes()
--> visitChildren() ------ [When reservedBytes() != 0] will acquire 'poolMutex_' again, **DEADLOCK!!**
```
So, `addAggregateChild()` indirectly calls `visitChildren()` [When
`reservedBytes() != 0`], causing a deadlock.
To solve this problem, the easiest way is to simplify the error message
printed when duplicate names appear. After all, we only need to know
the name of the parent pool, just like many other places in this class do.
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| void* buff = childOne->allocate(kChunkSize); | ||
| // Add child when 'reservedBytes != 0', in which case 'usedBytes()' will call | ||
| // 'visitChildren()'. | ||
| ASSERT_THROW(root->addAggregateChild("child_one"), VeloxRuntimeError); |
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s/ASSERT_THROW/VELOX_ASSERT_THROW/
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@xiaoxmeng has imported this pull request. If you are a Meta employee, you can view this diff on Phabricator. |
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@xiaoxmeng merged this pull request in 311e911. |
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Conbench analyzed the 1 benchmark run on commit There were no benchmark performance regressions. 🎉 The full Conbench report has more details. |
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Fixes #10342
MemoryPool::poolMutex_is used to protectMemoryPool::children_inthe following 4 member methods:
addLeafChild()/addAggregateChild()/getChildCount()/visitChildren.In other words, to avoid deadlock:
poolMutex_.holding
poolMutex_;these 4 methods. (This is the root cause of this problem).
addAggregateChild() ------ will acquire 'poolMutex_' --> toString() [When duplicate names appear, used to print error messages] --> usedBytes() --> visitChildren() ------ [When reservedBytes() != 0] will acquire 'poolMutex_' again, **DEADLOCK!!**So,
addAggregateChild()indirectly callsvisitChildren()[WhenreservedBytes() != 0], causing a deadlock.To solve this problem, the easiest way is to simplify the error message
printed when duplicate names appear. After all, we only need to know
the name of the parent pool, just like many other places in this class do.