FOR FREE CONTENT
- Introduction: OS
- Booting Process
- Command Interpreter
- Dual mode of operation
- System Calls
- Difference between system call and library call
- Interrupt and Trap
- Introduction
- Scheduling Criteria, Terms and Concepts
- Different Type Scheduling Algorithms
- Longest Job First
- Longest Remaining Time First
- Highest Response Ratio Next (HRRN)
- Priority Scheduling
- Least Completed Next (LCN) Scheduling
- Multi-Level Queue Scheduling
- Multilevel Feedback Queue Scheduling
- Guaranteed Scheduling
- Fair Share Scheduling
- Lottery Scheduling
- Multi-Processor Scheduling
- Deadline Scheduling
- Rate-Monotonic Scheduling
- POSIX Real-Time Scheduling
- Priority Inversion
- Proportional Share Scheduling
- Comparison table of Scheduling Algorithm
- Algorithm Evaluation for Scheduling
- Important concept of MM
- Memory Representation as Address
- Memory layout for a Process
- Logical and Physical Address Space
- Necessity of Memory Management
- Introduction
- Concept of Non-contiguous memory allocation
- Basic concept of Paging
- Address Translation
- Process of Paging Method
- Calculation of Offset for paging
- Calculation of Logical Address Bit and number of Pages
- Calculation of Physical Address Bit and number of Frames
- Calculation of Page Table Size
- Organization of MMU
- Why Page size power of 2
- Paging Address Calculation: example1
- Paging Numeric Problem: Example2
- Paging Address Calculation: Example3
- Paging Address Calculation: Question1
- Some Important Question 2
- Paging Address Translation: Question3
- UGC NET Paging Question
- GATE Paging Question
- Number of information at Page Entry
- Exams Question on Page Entry Information
- Exam Question: Page Entry Information
- Calculates Page Table Entry Size
- Calculates Page Size
- Calculation of Optimal Page Size
- Question on Optimal Page Size
- Hashed Page Table with Example
- Inverted Page Table with Gate Question
- Question on Inverted Page Table
- Multi-Level Paging
- Multi-level paging: Example1
- Multi-level paging: Example2
- Allocation of Frames
- Subject Mock
Cigarette Smokers problem
In this problem, four processes are there, three smokers and one supplier process. Cigarette requires tobacco, paper, and matches. Three smokers have the ability to supply one of the three items (tobacco, paper, matches) and the supplier has the ability to supply all three ingredients (tobacco, paper, matches).
Now, agents palaces two random ingredients on the table and the smokers sitting around the table supply the third ingredient to makes the cigarette.
Once the cigarette has been finished, again same procedure will be applied to make the cigarette.
This problem can lead to a deadlock or race-around condition. Because let supplier places tobacco and matches on the table and it selects one of the smokers who can supply matches and go to sleep. Now here selected smoker unable to make their cigarette because smoker who can supply paper was not selected. Now, the supplier is in sleep after ingredients and smokers also go to sleep because they can’t make a cigarette. All processes going to sleep forever which leads to a deadlock.
Solutions
So, the algorithm is very simple where three smokers make a cigarette and consume it. If they can't make the cigarette, then they go to sleep.
The supplier process provides any of two ingredients and wakes the proper smoker and goes to sleep.
Here four semaphores are used for three smokers and one supplier. One semaphore is used for mutual exclusion i.e. mutex.
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