On 01/05/15 12:06 am, Abhijit Bhopatkar wrote:
There is a possibility of a receiver losing out on messages in certain
corner conditions. One of the buggy case is if there is are two sender
ready with messages to be sent. Sender 1 initially gets the TOKEN lock
and proceeds.
After initial processing the sender of message 1 _will_ release TOKEN as
soon as receiver releases ACK, it does not wait till ACK CR is
re-acquired by receiver.
I could not come up with any solution except to add one more lock
resource for now we will call it "SYNC"
Sender 1 Sender2 Receiver
Get EX on TOKEN Get EX on TOKEN
Get EX on SYNC <Wait till granted>
<Granted>
Get EX on MSG
write LVB
down MSG to CR
Get EX of ACK
<wait till granted> BAST for ACK
Get CR on MSG
read LVB
<process>
Queue EX on SYNC
release ACK
AST for ACK
down ACK to CR
release MSG
release SYNC
release TOKEN
SYNC granted
<granted>
Get EX on SYNC
<wait till grant>
Get EX on MSG
Get CR on ACK
release MSG
release SYNC
Get EX on MSG
<....proceed rest>
release TOKEN
The key thing to note here is that the SYNC lock request is only queued
in receiver path. Having worked in dlm before I know for sure this will
work as expected.
Abhijit
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