[Sblim-issues] [ sblim-Bugs-1838961 ] sfcb hangs due to potential deadlock in upcalls

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Bugs item #1838961, was opened at 2007-11-26 15:35
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Category: sfcb
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Chris Buccella (buccella)
Assigned to: Chris Buccella (buccella)
Summary: sfcb hangs due to potential deadlock in upcalls

Initial Comment:
Lets say that a user can do an enumerate instances (ei) on 2 classes, Class X and Class M.

Now, lets say that 
1. An ei on Class X is implemented by doing an upcall to ei Class Y which in
turn does an ei on Class Z.

2. An ei on Class M is implemented by doing an upcall to ei Class N which in
turn does an ei on Class O.

And, lets say we have 3 providers and they implement the following classes.
1. Provider A (in group A), it implements the classes
   Class X
   Class N

2. Provider B (in group B), it implements the classes
   Class Y
   Class M

3. Provider C (in group C), it implemenst the classes
   Class O
   Class Z


Now, we could end up in a scenario where:
1. Class X has acquired the lockUpcall mutex in brokerUpc.c in provider A and is doing an ei on Class Y.

2. Class M has acquired the lockUpcall mutex in brokerUpc.c in provider B and is doing an ei on Class N.

3. Now, Class Y is waiting for the mutex acquired in step 2 above to do an upcall to Class Z

4. And Class N is waiting for the mutex acquired in step 1 above to do an upcall to Class O.

In this scenario we seem to hit a deadlock and sfcb hangs forever.

(bug found by Mahesh Patil)

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