Resource Management

OSS (operating system similator) is a program that simulates an operating system.

Resources are managed by OSS. User processes request resources. OSS will then check if that resources is available. If the resource is available, then OSS will run the Banker's Algorithm to check if there is a safe sequence after the resource is granted. If there is a safe sequence, then OSS will grant the resource. If there is not a safe sequence then OSS will put the requesting process in a blocked queue. OSS will check the blocked queue every time a resource is released to see if any blocked processes can be unblocked.

Safe Sequences

A safe sequence is an ordering of processes. For example, <P2, P4, P0, P1, P3> could be a safe sequence and that would mean that P2 could finish executing and then would release its resources. Then, P4 would finish executing and release its resources, and so on until all the processes have finished executing and all the resources have been released. Thus, a safe sequence gurantees that there cannot be a deadlock.

OSS and User Process Communication

User processes communicate to OSS that they are requesting or releasing a resource by sending OSS a message through a message queue. After sending a message to request/release a resource, the user process will use a blocking receive to receive a response message from OSS. Thus, the user process will not continue executing until a response is received.

Program Hanging

The program has a low probability to stall for a reason that I have not been able to figure out. If that happens, then press ctrl-c to exit the program and try running it again.

The program will generate a log file called oss.log. Use the -v (verbose) flag to have more information printed to the console and log file.

To build this program run:

make

To run this program:

./oss

To run this program in verbose mode:

./oss -v

To cleanup run:

make clean

Below is my git log:

0703d7b 2018-04-09 17:18:31 -0500 Add more information to README
a68c369 2018-04-08 08:15:47 -0500 Add verbose mode
63d8ba2 2018-04-07 20:33:40 -0500 Add total wait time to statistics
a66ec98 2018-04-07 20:02:04 -0500 Add statistics
4710dd7 2018-04-07 19:26:38 -0500 Test/debug program
d535610 2018-04-06 19:55:36 -0500 Check if we can unblock more than 1 process per resource when process terminate
3088948 2018-04-06 19:41:03 -0500 Test blocked queue
89f8b5f 2018-04-06 18:07:30 -0500 Implment blocked queue
bcc0e31 2018-04-06 17:33:36 -0500 Add print rsc summary function and blocked queue
d9b5e5a 2018-04-06 16:43:23 -0500 Cleanup OSS
44f87e2 2018-04-06 16:08:33 -0500 Change message receive function
354edbb 2018-04-01 08:04:33 -0500 Cleanup OSS main loop
eef4ce0 2018-04-01 07:48:36 -0500 Debug and move resource functions from bankers file into resources file
02e84b5 2018-03-31 19:44:20 -0500 Refactor rsc table print functions to also print to file
b752d4c 2018-03-31 19:27:43 -0500 Move resource functions from user program into resource file
33ed701 2018-03-31 15:40:37 -0500 Add logic so user only requests a resource if allocated is less than max claims
603b7a0 2018-03-31 13:56:55 -0500 Add TBDs for more OSS logic
0049183 2018-03-31 13:33:32 -0500 Move get max rsc claims function into resource file
e252a0e 2018-03-31 13:29:03 -0500 Refactor resources functions from OSS into resources file
313a087 2018-03-31 13:04:21 -0500 Finish bankers algorithm
ad9d7ba 2018-03-31 12:45:33 -0500 Fix build errors
dba55e3 2018-03-31 12:36:19 -0500 Refactor bankers algorithm into its own file
39ee351 2018-03-30 19:20:43 -0500 Add bankers algorithm logic
cce829d 2018-03-30 18:34:21 -0500 Add bankers algorithm
640e48c 2018-03-30 15:28:48 -0500 Lower request/release time for user program
6187f08 2018-03-30 14:38:52 -0500 Add message parsing logic to OSS
2b0b0a2 2018-03-29 20:00:33 -0500 Add rcv msg no wait function
2a8e00e 2018-03-29 19:38:13 -0500 Add get available pid function
c851a5a 2018-03-29 19:17:51 -0500 Refactor msg coordination, add TBD comments
d706f46 2018-03-29 18:29:44 -0500 Get number of allocated resources function
c8a2fc2 2018-03-29 17:17:30 -0500 Fix errors and warning messages in user program
e776dbf 2018-03-29 17:06:53 -0500 Refactor request/release logic into functions
b6576d6 2018-03-29 16:53:07 -0500 Add release resource logic to user program
1897fd7 2018-03-29 14:24:21 -0500 Refactor user program
6902dbe 2018-03-29 14:15:19 -0500 Cleanup user program
ed6e008 2018-03-29 13:52:51 -0500 Add request rsc logic to user
95a5e7b 2018-03-29 13:25:30 -0500 Fix bug in print allocated resource table
3a3a4af 2018-03-29 13:20:23 -0500 Add print allocated resource table function
f01882a 2018-03-27 21:22:16 -0500 Add allocated array and stub user program
181a7c4 2018-03-27 07:11:06 -0500 Cleanup user program
1d78e0b 2018-03-27 06:57:45 -0500 Cleanup user program
794f2b8 2018-03-27 06:15:40 -0500 Add allocation of resource table
ac65136 2018-03-27 06:06:44 -0500 Update user for new shared memory structures
e58e5f6 2018-03-27 06:01:50 -0500 Add shared memory structures
8b21d62 2018-03-25 20:08:35 -0500 First commit