Avoid unsynchronized access to scheduledTaskQueue in GlobalEventExecutor#10890
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normanmaurer merged 1 commit intonetty:4.1from Dec 24, 2020
Merged
Avoid unsynchronized access to scheduledTaskQueue in GlobalEventExecutor#10890normanmaurer merged 1 commit intonetty:4.1from
normanmaurer merged 1 commit intonetty:4.1from
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Motivation:
A race detector discovered a data race in GlobalEventExecutor present in
netty 4.1.51.Final:
```
Write of size 4 at 0x0000cea08774 by thread T103:
#0 io.netty.util.internal.DefaultPriorityQueue.poll()Lio/netty/util/internal/PriorityQueueNode; DefaultPriorityQueue.java:113
netty#1 io.netty.util.internal.DefaultPriorityQueue.poll()Ljava/lang/Object; DefaultPriorityQueue.java:31
netty#2 java.util.AbstractQueue.remove()Ljava/lang/Object; AbstractQueue.java:113
netty#3 io.netty.util.concurrent.AbstractScheduledEventExecutor.pollScheduledTask(J)Ljava/lang/Runnable; AbstractScheduledEventExecutor.java:133
netty#4 io.netty.util.concurrent.GlobalEventExecutor.fetchFromScheduledTaskQueue()V GlobalEventExecutor.java:119
netty#5 io.netty.util.concurrent.GlobalEventExecutor.takeTask()Ljava/lang/Runnable; GlobalEventExecutor.java:106
netty#6 io.netty.util.concurrent.GlobalEventExecutor$TaskRunner.run()V GlobalEventExecutor.java:240
netty#7 io.netty.util.internal.ThreadExecutorMap$2.run()V ThreadExecutorMap.java:74
netty#8 io.netty.util.concurrent.FastThreadLocalRunnable.run()V FastThreadLocalRunnable.java:30
netty#9 java.lang.Thread.run()V Thread.java:835
netty#10 (Generated Stub) <null>
Previous read of size 4 at 0x0000cea08774 by thread T110:
#0 io.netty.util.internal.DefaultPriorityQueue.size()I DefaultPriorityQueue.java:46
netty#1 io.netty.util.concurrent.GlobalEventExecutor$TaskRunner.run()V GlobalEventExecutor.java:263
netty#2 io.netty.util.internal.ThreadExecutorMap$2.run()V ThreadExecutorMap.java:74
netty#3 io.netty.util.concurrent.FastThreadLocalRunnable.run()V FastThreadLocalRunnable.java:30
netty#4 java.lang.Thread.run()V Thread.java:835
netty#5 (Generated Stub) <null>
```
The race is legit, but benign. To trigger it requires a TaskRunner to
begin exiting and set 'started' to false, more work to be scheduled
which starts a new TaskRunner, that work then needs to schedule
additional work which modifies 'scheduledTaskQueue', and then the
original TaskRunner checks 'scheduledTaskQueue'. But there is no danger
to this race as it can only produce a false negative in the condition
which causes the code to CAS 'started' which is thread-safe.
Modifications:
Delete problematic references to scheduledTaskQueue. The only way
scheduledTaskQueue could be modified since the last check is if another
TaskRunner is running, in which case the current TaskRunner doesn't
care.
Result:
Data-race free code, and a bit less code to boot.
normanmaurer
approved these changes
Dec 24, 2020
normanmaurer
pushed a commit
that referenced
this pull request
Dec 24, 2020
…tor (#10890) Motivation: A race detector discovered a data race in GlobalEventExecutor present in netty 4.1.51.Final: ``` Write of size 4 at 0x0000cea08774 by thread T103: #0 io.netty.util.internal.DefaultPriorityQueue.poll()Lio/netty/util/internal/PriorityQueueNode; DefaultPriorityQueue.java:113 #1 io.netty.util.internal.DefaultPriorityQueue.poll()Ljava/lang/Object; DefaultPriorityQueue.java:31 #2 java.util.AbstractQueue.remove()Ljava/lang/Object; AbstractQueue.java:113 #3 io.netty.util.concurrent.AbstractScheduledEventExecutor.pollScheduledTask(J)Ljava/lang/Runnable; AbstractScheduledEventExecutor.java:133 #4 io.netty.util.concurrent.GlobalEventExecutor.fetchFromScheduledTaskQueue()V GlobalEventExecutor.java:119 #5 io.netty.util.concurrent.GlobalEventExecutor.takeTask()Ljava/lang/Runnable; GlobalEventExecutor.java:106 #6 io.netty.util.concurrent.GlobalEventExecutor$TaskRunner.run()V GlobalEventExecutor.java:240 #7 io.netty.util.internal.ThreadExecutorMap$2.run()V ThreadExecutorMap.java:74 #8 io.netty.util.concurrent.FastThreadLocalRunnable.run()V FastThreadLocalRunnable.java:30 #9 java.lang.Thread.run()V Thread.java:835 #10 (Generated Stub) <null> Previous read of size 4 at 0x0000cea08774 by thread T110: #0 io.netty.util.internal.DefaultPriorityQueue.size()I DefaultPriorityQueue.java:46 #1 io.netty.util.concurrent.GlobalEventExecutor$TaskRunner.run()V GlobalEventExecutor.java:263 #2 io.netty.util.internal.ThreadExecutorMap$2.run()V ThreadExecutorMap.java:74 #3 io.netty.util.concurrent.FastThreadLocalRunnable.run()V FastThreadLocalRunnable.java:30 #4 java.lang.Thread.run()V Thread.java:835 #5 (Generated Stub) <null> ``` The race is legit, but benign. To trigger it requires a TaskRunner to begin exiting and set 'started' to false, more work to be scheduled which starts a new TaskRunner, that work then needs to schedule additional work which modifies 'scheduledTaskQueue', and then the original TaskRunner checks 'scheduledTaskQueue'. But there is no danger to this race as it can only produce a false negative in the condition which causes the code to CAS 'started' which is thread-safe. Modifications: Delete problematic references to scheduledTaskQueue. The only way scheduledTaskQueue could be modified since the last check is if another TaskRunner is running, in which case the current TaskRunner doesn't care. Result: Data-race free code, and a bit less code to boot.
raidyue
pushed a commit
to raidyue/netty
that referenced
this pull request
Jul 8, 2022
…tor (netty#10890) Motivation: A race detector discovered a data race in GlobalEventExecutor present in netty 4.1.51.Final: ``` Write of size 4 at 0x0000cea08774 by thread T103: #0 io.netty.util.internal.DefaultPriorityQueue.poll()Lio/netty/util/internal/PriorityQueueNode; DefaultPriorityQueue.java:113 netty#1 io.netty.util.internal.DefaultPriorityQueue.poll()Ljava/lang/Object; DefaultPriorityQueue.java:31 netty#2 java.util.AbstractQueue.remove()Ljava/lang/Object; AbstractQueue.java:113 netty#3 io.netty.util.concurrent.AbstractScheduledEventExecutor.pollScheduledTask(J)Ljava/lang/Runnable; AbstractScheduledEventExecutor.java:133 netty#4 io.netty.util.concurrent.GlobalEventExecutor.fetchFromScheduledTaskQueue()V GlobalEventExecutor.java:119 netty#5 io.netty.util.concurrent.GlobalEventExecutor.takeTask()Ljava/lang/Runnable; GlobalEventExecutor.java:106 netty#6 io.netty.util.concurrent.GlobalEventExecutor$TaskRunner.run()V GlobalEventExecutor.java:240 netty#7 io.netty.util.internal.ThreadExecutorMap$2.run()V ThreadExecutorMap.java:74 netty#8 io.netty.util.concurrent.FastThreadLocalRunnable.run()V FastThreadLocalRunnable.java:30 netty#9 java.lang.Thread.run()V Thread.java:835 netty#10 (Generated Stub) <null> Previous read of size 4 at 0x0000cea08774 by thread T110: #0 io.netty.util.internal.DefaultPriorityQueue.size()I DefaultPriorityQueue.java:46 netty#1 io.netty.util.concurrent.GlobalEventExecutor$TaskRunner.run()V GlobalEventExecutor.java:263 netty#2 io.netty.util.internal.ThreadExecutorMap$2.run()V ThreadExecutorMap.java:74 netty#3 io.netty.util.concurrent.FastThreadLocalRunnable.run()V FastThreadLocalRunnable.java:30 netty#4 java.lang.Thread.run()V Thread.java:835 netty#5 (Generated Stub) <null> ``` The race is legit, but benign. To trigger it requires a TaskRunner to begin exiting and set 'started' to false, more work to be scheduled which starts a new TaskRunner, that work then needs to schedule additional work which modifies 'scheduledTaskQueue', and then the original TaskRunner checks 'scheduledTaskQueue'. But there is no danger to this race as it can only produce a false negative in the condition which causes the code to CAS 'started' which is thread-safe. Modifications: Delete problematic references to scheduledTaskQueue. The only way scheduledTaskQueue could be modified since the last check is if another TaskRunner is running, in which case the current TaskRunner doesn't care. Result: Data-race free code, and a bit less code to boot.
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Motivation:
A race detector discovered a data race in GlobalEventExecutor present in
netty 4.1.51.Final:
The race is legit, but benign. To trigger it requires a TaskRunner to
begin exiting and set 'started' to false, more work to be scheduled
which starts a new TaskRunner, that work then needs to schedule
additional work which modifies 'scheduledTaskQueue', and then the
original TaskRunner checks 'scheduledTaskQueue'. But there is no danger
to this race as it can only produce a false negative in the condition
which causes the code to CAS 'started' which is thread-safe.
Modifications:
Delete problematic references to scheduledTaskQueue. The only way
scheduledTaskQueue could be modified since the last check is if another
TaskRunner is running, in which case the current TaskRunner doesn't
care.
Result:
Data-race free code, and a bit less code to boot.