Consider this monitor solution to the readers/writers problem:

monitor Readers-Writers

int read_cnt = 0, writing = 0;

condition OK_to_read, OK_to_write;

start_read()

if (writing )

OK_to_read.wait;

read_cnt++;

OK_to_read.signal;



finish_read()

read_cnt--;

if (read_cnt == 0)

Ok_to_write.signal;



start_write()

if ((read_cnt != 0) || writing)

OK_to_write.wait;

writing = 1;



finish_write()

writing = 0;

if (!empty(OK_to_read))

OK_to_read.signal;

else

OK_to_write.signal;





reader:

…..

start_read();

/ reading here /

finish_read();

…..

writer:

…..

start_write();

/ writing here /

finish_write();

…..

Assume the first request is a writer W1. While W1 is executing/writing, the following requests arrive in the given order: W2, R1, R2, W3, R3, W4.

(1) In which order will these requests be processed? Which groups of readers will be reading concurrently?