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.
@chadj17972 жыл бұрын
Yep, this works too!
@napoleon32422 жыл бұрын
@@chadj1797 it's not "this works too!", it's how it's supposed to work
@eylulmood48302 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?
@aniketdas34069 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 :)
@shaneyaw45422 жыл бұрын
This was a good explanation of something that is not explained well in the textbooks. Good job.
@elconnero5 ай бұрын
Dude you are amazing, I am learning more in one video than a full lecture my professor gives.
@-shultz Жыл бұрын
12:18 readcnt >= 1 cuz if it is updated to more than 1 writer process can start updating .
@user-hg6lo8sj1h6 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
@shahinsheikh69642 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 ❤️
@justkflesh2 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.
@rabomeister Жыл бұрын
Cut off the bullshit and just study your thing.
@DevC-g9c28 күн бұрын
Good Explanation , but how wrt decide that whether the requested process is for reading or writing
@pranavbakare89223 жыл бұрын
This is one of the Best explanations!!!!!
@user-is6fq5xm7b11 ай бұрын
Thanks a lot... It was soo confusing before and this was soo helpful❤
@darshil-oh2le9 ай бұрын
Such a nice explaination , make topic very easy 📌📌
@rishujain0721 Жыл бұрын
Best explanation ❤ Our teacher taught this wrong in the class..dumb
@hecticgamings5 ай бұрын
Chota packet bada dhamka😂 Writers process 😊 readers process😮😢
@ABHISEKBISWASB2 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)?
@camuflagehugo51372 жыл бұрын
It would be nice if there was an implementation in C.
@nikhil789806 ай бұрын
now signal(wrt) means both readers and writers can access it right?
@anjalisoni237110 ай бұрын
Nice explanation thanks for supporting us!
@jajnyaseniswain8472 Жыл бұрын
Well explained,... Got every bit of this problem
@ayahamad59318 ай бұрын
May god bless you with the Health ❤❤
@user-ytuser Жыл бұрын
thanks, it was very nice explanation, crisp and clear
@marvolo60922 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?
@JohnR4362 жыл бұрын
Any suggestions?
@simon82842 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.
@bryanshi37742 жыл бұрын
Great video! Why do we need mutex semaphore to ensure the mutual exclusion of readcnt?
@bhaskarmishra84792 жыл бұрын
well, you may know about the race condition. To avoid it we need a mutex
@minhhoangcong9155 Жыл бұрын
@@bhaskarmishra8479 can you tell more about it ?
@luciec18892 жыл бұрын
Very well explained! Thank you so much!!
@cyberssam654 Жыл бұрын
Very nice explanation sir 👍👍
@adityarajsinghgour31132 жыл бұрын
@Neso Academy signal(mutex) is outside the if block or inside the if block ?
@danishsharma4962 жыл бұрын
outside \
@indian_otaku23882 жыл бұрын
#nesoacademy
@walidslimani3 ай 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
@avnarayana24142 ай 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
@dfged96542 жыл бұрын
Is the last signal(mutex) inside reader process having a wrong indentation?
@fritz66002 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)
@nitpal99582 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.
@NisargaChowdaiah5 ай бұрын
Thank you so much 😊
@hayden41272 жыл бұрын
that indenting is so confusing in reader process
@andrewbabilonia772 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.
@danishsharma4962 жыл бұрын
@@andrewbabilonia77 ya true I checked on Internet loll
@nainaparmar4105 Жыл бұрын
mutex is a binary semaphore , then wrt is counting semaphore?
@hetubhasingh4374 Жыл бұрын
Well explained
@manojkumarn4683 жыл бұрын
Thanks
@JonathanSteadman20032 жыл бұрын
Great video :)
@minhhoangcong9155 Жыл бұрын
I think the mutex for read count is no need
@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
@williamhogrider41363 ай бұрын
@@AmpangNation Yes I think you're right
@debarghyaadhikari5558 Жыл бұрын
Good one
@mohamedredha95862 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)
@danishsharma4962 жыл бұрын
more readers can be there , but writer can only come when readers become 0 so its signalling
@khomo12 Жыл бұрын
Very good explanation!
@samarthtandale9121 Жыл бұрын
Awesome !!!
@arfatbagwan4810 ай бұрын
Salute to you
@pamp3657 Жыл бұрын
good video
@azadr3 жыл бұрын
Pls upload in neso website and app also simultaneously
@rajeshprajapati48633 жыл бұрын
I think it's already there.
@azadr3 жыл бұрын
@@rajeshprajapati4863 no not all the video available
@rajeshprajapati48633 жыл бұрын
@@azadr OS Subject is complete on app and website too. Check Again.
@azadr3 жыл бұрын
@@rajeshprajapati4863not only with respective to os I was talking about all other subjects which were upload in youtube but not on neso