The Readers Writers Problem

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Күн бұрын

Operating System: The Readers Writers Problem
Topics discussed:
Classic Problems of Synchronization:
1. The Readers Writers Problem.
2. Solution to the Readers Writers Problem using Semaphores.
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#OperatingSystemByNeso #OperatingSystem #ProcessSynchronization #ReadersWritersProblem

Пікірлер: 80

@miloradowicz 2 жыл бұрын

I think the if (readcount == 1) wait(wrt); part would be best explained like this: when we are reading, no one should be allowed to write, thus the wrt semaphore should be acquired; so if we are the _first_ reader, we acquire it (and wait till it's released if someone's still writing); but if someone's already reading, it means they have already acquired wrt, so we just skip this part. Similarly, in the if (readcount == 0) signal(wrt); line, we check if we are the last reader, and if we are, it's our responsibility to release wrt, thus allowing others to write.

@chadj1797 2 жыл бұрын

Yep, this works too!

@napoleon3242 2 жыл бұрын

@@chadj1797 it's not "this works too!", it's how it's supposed to work

@eylulmood4830 Жыл бұрын

you're absolutly right

@ScopedKilz Жыл бұрын

You are the GOAT

@surajr4757 Жыл бұрын

Thank you so much, my doubt cleared from your comment, are you from Russia?

@shaneyaw4542 2 жыл бұрын

This was a good explanation of something that is not explained well in the textbooks. Good job.

@aniketdas3406 6 ай бұрын

If someone like me who's struggling to understand how multiple processes can read without allowing any other process to write, it can be explained in this way: When the first reader process enters it decrements the wrt and makes it 0 so that no writer process can execute untill the last reader has done its job and signals wrt. Therefore, after the first reader process, other readers which will try to read concurrently will skip the if(readcount ==1) part since wrt is already decremented by the first read process and write() operations are halted. I hope it helped you :)

@elconnero 2 ай бұрын

Dude you are amazing, I am learning more in one video than a full lecture my professor gives.

@pranavbakare8922 2 жыл бұрын

This is one of the Best explanations!!!!!

@user-ytuser Жыл бұрын

thanks, it was very nice explanation, crisp and clear

@user-is6fq5xm7b 8 ай бұрын

Thanks a lot... It was soo confusing before and this was soo helpful❤

@jajnyaseniswain8472 10 ай бұрын

Well explained,... Got every bit of this problem

@anjalisoni2371 7 ай бұрын

Nice explanation thanks for supporting us!

@-shultz Жыл бұрын

12:18 readcnt >= 1 cuz if it is updated to more than 1 writer process can start updating .

@shahinsheikh6964 Жыл бұрын

I am studying in the morning and today is my exam belive me i wasnt able to understand and was very tensed and frustrated bcoz of this topic but when i visited this channel i felt its soo easy.. thanku so much ❤️

@darshil-oh2le 7 ай бұрын

Such a nice explaination , make topic very easy 📌📌

@khomo12 Жыл бұрын

Very good explanation!

@cyberssam654 Жыл бұрын

Very nice explanation sir 👍👍

@luciec1889 2 жыл бұрын

Very well explained! Thank you so much!!

@justkflesh 2 жыл бұрын

It is interesting. When the lecture becomes more complex, the views drop significantly. I am very thank you, you keep sharing your knowledge.

@huseyinsenol1769 Жыл бұрын

Cut off the bullshit and just study your thing.

@user-hg6lo8sj1h 4 ай бұрын

i have one doubt imagine 2 reader and default mutex is 1 . if 1st reader comes in wait he makes mutex to 0 .Inside if condition reader1 will restrict writer .After restricting writer he is allowing one more reader by signal(mutex) so mutex is 1 .reader 2 uses this and now mutex is 0 and reader 2 again increases to 1 . if user 1 has to level. before leaving wait(mutex) he will perform so it will 0 now if reader 2 has to leave he has to perform wait(mutex) now its a dead lock for reader2 any body can explain

@camuflagehugo5137 2 жыл бұрын

It would be nice if there was an implementation in C.

@nikhil78980 3 ай бұрын

now signal(wrt) means both readers and writers can access it right?

@rishujain0721 11 ай бұрын

Best explanation ❤ Our teacher taught this wrong in the class..dumb

@hetubhasingh4374 Жыл бұрын

Well explained

@NisargaChowdaiah 2 ай бұрын

Thank you so much 😊

@bryanshi3774 2 жыл бұрын

Great video! Why do we need mutex semaphore to ensure the mutual exclusion of readcnt?

@bhaskarmishra8479 2 жыл бұрын

well, you may know about the race condition. To avoid it we need a mutex

@minhhoangcong9155 11 ай бұрын

@@bhaskarmishra8479 can you tell more about it ?

@nainaparmar4105 Жыл бұрын

mutex is a binary semaphore , then wrt is counting semaphore?

@JonathanSteadman2003 2 жыл бұрын

Great video :)

@adityarajsinghgour3113 2 жыл бұрын

@Neso Academy signal(mutex) is outside the if block or inside the if block ?

@danishsharma496 Жыл бұрын

outside \

@indian_otaku2388 Жыл бұрын

#nesoacademy

@manojkumarn468 2 жыл бұрын

Thanks

@marvolo6092 2 жыл бұрын

this program seems to give more priority to the read operations. So going by the code, once a read operation acquires the wrt semaphore, it will only release it if readcount is 0 - thus if read processes keep coming in, I believe it will cause starvation for the write process, isn't it? So bounded waiting for effective process synchronization is not satisfied. How to improve this to implement bounded waiting?

@JohnR436 2 жыл бұрын

Any suggestions?

@simon8284 2 жыл бұрын

Do we have to learn these codes for theory exams or its just to learn the basic theory?

@dhyansai6186 Жыл бұрын

I guess we need to create an other semaphore to maintain a queue that involves both readers as well as writers.

@ayahamad5931 6 ай бұрын

May god bless you with the Health ❤❤

@debarghyaadhikari5558 Жыл бұрын

Good one

@samarthtandale9121 10 ай бұрын

Awesome !!!

@ABHISEKBISWASB Жыл бұрын

I think the signal(mutex) should come before : if(readcnt==0) so that after decrementing the readcnt the other readers can enter before releasing the wrt

@30benasabu65 Жыл бұрын

I think you have missed something the control goes to readcnt==0 if there are no readers left so in such a case the wrt lock must be released and mutex must also be released, The mutex lock held by a reader is released after it enters the critical section (given as signal mutex), so this ensures other readers can enter the critical section. here indentations are used to separate the code you may have missed it.

@reverbism Жыл бұрын

@@30benasabu65 can Signal(mutex) come before the signal(wrt)?

@dfged9654 2 жыл бұрын

Is the last signal(mutex) inside reader process having a wrong indentation?

@fritz6600 2 жыл бұрын

They're following c style syntax for writing their pseudocode, in C if (...) statement1; is same as doing if (...) {statement1; statement 2; ....} Which is to say, immediately execute whatever that comes after "if", if "if's" condition is true, that "whatever" can be a block of statements or a single statement. Edit: Indentation does not matter in C, all that matters is, semicolon and curly braces. Edit2: int main() needs a curly-brace because int main is a function definition. Function definition needs curly braces. (Why? I do not know)

@nitpal9958 2 жыл бұрын

I think so too. Doesn't make sense to wait till the last reader to release mutex. Correct me if I'm wrong.

@mohamedredha9586 2 жыл бұрын

if readcoun==0 signal wrt / why should we wait all the readers to execute so we allow the writer to enter , perhaps the writer was there before some numbers of writers came , isnt this a sort of privilege that shouldn't happen in mutual exclusion ? (sorry for this broken English lol)

@danishsharma496 Жыл бұрын

more readers can be there , but writer can only come when readers become 0 so its signalling

@pamp3657 Жыл бұрын

good video

@arfatbagwan48 7 ай бұрын

Salute to you

@hayden4127 2 жыл бұрын

that indenting is so confusing in reader process

@andrewbabilonia77 2 жыл бұрын

I believe this is the proper indentation. do { wait(mutex); readcount++; if(readcount == 1) wait(wrt); signal(mutex); /*current reader performs reading*/ wait(mutex); readcount--; if(readcount == 0) signal(wrt); signal(mutex); }while(TRUE); please correct if I'm wrong.

@danishsharma496 Жыл бұрын

@@andrewbabilonia77 ya true I checked on Internet loll

@minhhoangcong9155 11 ай бұрын

I think the mutex for read count is no need

@walidslimani 21 күн бұрын

i mean if you think about it . a reader is like a consumer and a writer is like a productor . so why not same logic

@avnarayana2414 5 күн бұрын

In readers writers problem we are used bounded buffer with fixed size and at there our main goal is to prevent overflow and underflow. But at readers writers problem the process is accessing shared resources like database or files. Here our goal is to allow concurrent reads and exclusive writes. Like this there are various key differences between those two problems bro

@hecticgamings 3 ай бұрын

Chota packet bada dhamka😂 Writers process 😊 readers process😮😢

@azadr 2 жыл бұрын

Pls upload in neso website and app also simultaneously

@rajeshprajapati4863 2 жыл бұрын

I think it's already there.

@azadr 2 жыл бұрын

@@rajeshprajapati4863 no not all the video available

@rajeshprajapati4863 2 жыл бұрын

@@azadr OS Subject is complete on app and website too. Check Again.

@azadr 2 жыл бұрын

@@rajeshprajapati4863not only with respective to os I was talking about all other subjects which were upload in youtube but not on neso

@mosheklein5090 Жыл бұрын

I see a problem with this solution : while reader 1 is currently reading, reader 2 can enter, readcnt is now =2, reader 1 finishes reading, he can’t continue to next line because the condition of readcnt ==0 isnt met. Now that readcnt is ==1 again, reader 2 continues. Now At this same time reader 2 can’t continue either because she cant get past the wait(wrt) condition since the lock is still held by reader 1. Reader 1 is waiting for reader 2 and vice versa. A traffic jam indeed!

@AmpangNation Жыл бұрын

last line signal(mutex) shouldn't be in the indentation (if statement), should be outside of the if statement, so that it won't have this problem I guess

@williamhogrider4136 18 күн бұрын

@@AmpangNation Yes I think you're right