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Read modify write is atomic operation which in first step read contents from a memory location, in second update it and finally re-write to the same location. No interrupt can stop of the process execution.
Also I found similar explanation in Wiki https://en.wikipedia.org/wiki/Read-modify-write
Enjoy
1. RMW can be an instruction in some protocols. In such case, this has to be atomic (as exlained in the above post).
2. RMW is the process of Error correction in the ECC based designs. When data is read from a memory with ECC support, first data is read and its ECC is computed and compared with the read ECC; if this matches pass the read data to the user, if this does not match, then we have to correct (if possible) and write the data back to memory while giving the corrected data to the user.
Supplementery answer to above replys:
Look at the following senario:
supose we have 2 process which each one increment common variable, for example CV.
for this reason if process 1 going to increment CV, first it read CV then increment its value but if before writing new value interrupt happen and control variable give to process 2.
process 2 do its task and read CV and incremet its value.
then control give to process 1, and process 1 write its old computed value to CV!!!
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