Problems with the current airport.c(after commit fff22f4) about os-assignment-2 HOT 5 CLOSED

Using 'fflush(stdout);' solved this:

Unable to access data from the 'msg_recv_atc'.

The issue previously might be caused because of buffering. The standard output might be buffered, and the buffer might not be flushed before the program exits or enters the next iteration of the loop.

from os-assignment-2.

In the commit "2f26369", whenever a msg will appear in the msg queue from the ATC, a new thread is being created and a suitable runway is being found out. If there is no suitable runway, backup runway is assigned.
Also,

Have to confirm the method of using 'val' in line 136.

is solved.

from os-assignment-2.

The following part:

Not sure about the usage of mutex. In the current code, lock is used only during the boarding/deboarding and takeoff/landing delays(sleep(2) and sleep(3)). What about the condition that no other plane should be given a runway when it is allotted another plane.

can be solved by using a 'runway_mutex'. This should allow a runway in an airport to be used by only one thread until the following are completed:

For Departure Airport:

• boarding/loading time(3sec)
• takeoff time(2sec)
• send msg to ATC through msg queue

For Arrival Airport:

• Plane travel time(30 sec) after receiving signal from the ATC
• landing time(2sec)
• deboarding/unloading time(3sec)
• send signal to ATC through msg queue

from os-assignment-2.

The commit 'eb0daeb' has improved this issue. An array of locks 'runway_mutex' is used. So each runway will have its own lock. If a runway is selected by a thread, it cannot be accessed by another thread unless the former exits. But at the same time this might lead to lack of security to shared resources. So, we should check what are the shared resources which get affected.

Also, there is some abnormal behavior when multiple planes try to depart/arrive at same airports. Data is getting corrupted in this case as there is no protection to shared resources.

from os-assignment-2.

Since the basic questions of this issue have been solved, this is being closed. The solution to the synchronization and abnormal results issue will be addressed in another issue or discussion.

from os-assignment-2.