Synchronization problem in message queue mechanism

Sebastian Huber sebastian.huber at
Thu Aug 22 13:29:59 UTC 2013

On 2013-08-22 15:23, Joel Sherrill wrote:
>> If I compare the functions _Event_Timeout() and _Thread_queue_Process_timeout()
>> I am a bit surprised that _Thread_queue_Process_timeout() doesn't use
>> _ISR_Disable/Enable() to protect the access to the_thread_queue->sync_state.
>> On a first glance this looks like a major bug.
> The assumption is that _Thread_queue_Process_timeout() is called from a clock tick
> ISR but thinking that doesn't prevent a nested interrupt from occurring.
> Does this system nest interrupts?

The event bug could happen without nested interrupts.  Anyway nested interrupts 
must be supported.

Sebastian Huber, embedded brains GmbH

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