Skip to main content

Priority Inheritance Protocol

    The use of Priority inheritance allows to avoid the priority inversion problem.


    Under this scheme, if a high priority task T1 is blocked by a lower priority task T2 (because T2 is currently executing a critical section needed by T1), the lower priority task temporarily inherits the priority of T1. When the blocking stops, T2 resumes its original priority.


  1. If a task T1 is blocked by T2 (due to contention for a critical section) and The priority of T1 is greater than T2, task T2 inherits the priority of T1 as long as it blocks T1. when T2 exits the critical section, it reverts to its original priority .

  3. Priority inheritance is transitive. If T3 blocks, which blocks T1(with T1 being the highest priority, T2 the medium priority and T3 being the lower priority), then T3 inherits the priority of T1 through T2.

    Disadvantages of PIP

    Priority inheritance can lead to deadlock during the following situation


    Consider two tasks T1 and T2 uses two critical sections S1 and S2 in the following order


    T1: Lock S1; Lock S2;Unlock S2; Unlock S1

    T2: Lock S2; Lock S1;Unlock S1; Unlock S2


  5. Assume T1 is having higher priority over T2.  Suppose T2 starts execution at Time t0. At time t1, it locks S2.
  6. At time t2, T1 is initiated and it preempts T2 owing to its higher priority.
  7. At time t3, T1 locks S1.
  8. At time t4, T1 attempts to lock S2, which is being locked by T2. so T2 inherits the priority of T1 and starts executing,
  9. At time t5, T2 tries to lock S1, which is locked by T1.
  10. So both the tasks are now deadlocked.

    This problem can be avoided by means of implementing priority Ceiling protocol


Popular posts from this blog

Installing TexLive 2019 in Ubuntu 18.04

Installation of TexLive 2019 in Linux (Ubuntu 18.04 LTS)
TeX (Tech)

Installation of TexLive 2019

Please watch the video for full installation

I used .iso file to download, the Total size is 3.3GB for Linux,

and i used the torrent file to download, it took me just 20 min to download the entire .iso file

Extract the .iso file to a folder and open a terminal

$] sudo ./install-tl
(it goes into a terminal mode, which is faster compared to the GUI Mode)

$] sudo ./install-tl -gui
after the installation, set the PATH, MANPATH and INFOPATH as suggested by LATEX

export PATH=$PATH:/usr/local/texlive/2019/bin/x86_64-linux
export MANPATH=/usr/local/texlive/2019/texmf-dist/doc/man
export INFOPATH=/usr/local/texlive/2019/texmf-dist/doc/info

put these lines in to the /home/pradeepkumar/.bashrc

$] gedit /home/pradeepkumar/.bashrc
We have installed TexLive 2019 and texstudio.

To install texstudio

$] sudo apt install texstudio
The look and feel of TexStudio looks like this image.

texlive, it install everyt…

Implementing a new system call in Kernel version 2.6.32

A system call is used by application or user programs to request service from the operating systems. Since the user programs does not have direct access to the kernel whereas the OS has the direct access. OS can access the hardware through system calls only.The following files has to be modified for implementing a system call/usr/src/linux- set of files to be createdCreate a new directory newcall/ inside the path “/usr/src/linux-” Create new files Makefile, newcall.c and put them in the /usr/src/linux- folder Create new user files (in any folder of Linux) to test the system call
testnewcall.c, testnewcall.h (created in /home/pradeepkumar) syscall_table_32.S Find the file /usr/src/linux- and add the following line at the end

Electrical Machine Design (equations)

FactorsDC Machine Transformers Induction Machines Synchronous MachinesOutput EquationPa=CoD2Ln, where Pa=P/h for generators, Pa=P for motorsFor Single Phase
Q=2.22 f Bm Ai Kw Aw d10-3
For Three Phase
Q=3.33 f Bm Ai Kw Aw d 10-3Q=CoD2 L ns
KVA Input Q=
HP * 0.746 / Cos f * hQ=CoD2 L ns
KVA Input Q=
HP * 0.746 / Cos f * h
For Turbo alternators
Q=1.11Bavac KwsVa2 L 10-3/nsOutput CoefficientCo=Bav ac* 10-3where Bav-magnetic loading and ac - electric loadingDNACo=11 Kws Bav ac 10-3Co=11 Kws Bav ac 10-3 Choice of Magnetic LoadingFlux Density in Teeth Frequency of Flux Reversals Size of machineDNAMagnetizing current, Flux Density, Iron lossIron loss, Stability, Voltage Rating, Parallel Operation, Transient ShortCircuit current Choice of Electric LoadingTemperature rise,
speed of machine, Voltage, Armature reaction, CommutationDNAOverload Capacity, Copper losses, Temperature rise, Leakage ReactanceCopper loss, Synchronous reactance, Temperature rise, Stray Load losses,
Voltage rating Flux …