Waiting For A Synchronized Method

[cppaddict]

Say thread1 begins executing a synchronized method.

While it's executing, both thread2 and thread3 call the synchronized
method, in that order.

When thread1 ends executing and gives up its lock, is thread2
guaranteed to execute next (because it's been waiting longer than
thread3), or is it possible that thread3 executes first?

My experiments seem to point to thread2 always running first in the
above situation, but I'd like to verify this.

Thanks,
John

 

[Chris Uppal]

Say thread1 begins executing a synchronized method.

While it's executing, both thread2 and thread3 call the synchronized
method, in that order.

When thread1 ends executing and gives up its lock, is thread2
guaranteed to execute next
No.

or is it possible that thread3 executes first?

Yes. Or rather, it is implementation-dependent, so don't assume anything.

-- chris

 

[Frank]

Say thread1 begins executing a synchronized method.

While it's executing, both thread2 and thread3 call the synchronized
method, in that order.

When thread1 ends executing and gives up its lock, is thread2
guaranteed to execute next (because it's been waiting longer than
thread3), or is it possible that thread3 executes first?

My experiments seem to point to thread2 always running first in the
above situation, but I'd like to verify this.

Thanks,
John

There is no guarantee which thread will recieve the lock after thread 1
has completed it's run. Generally, the OS gives a slight preference first
to the thread with the higher priority, then to the thread that has been
waiting the longest. However, this is just a guideline, and does not
suggest a requirement on behalf of the implementation. As I said before,
there are no guarantees.

HTH

-Frank