Reader/Writer with Semaphores: Take 2

SharedLock::AcquireRead() {

rblock.P();

rmx.P();

if (first reader)

wsem.P();

rmx.V();

rblock.V();

}

SharedLock::ReleaseRead() {

rmx.P();

if (last reader)

wsem.V();

rmx.V();

}

SharedLock::AcquireWrite() {

wmx.P();

if (first writer)

rblock.P();

wmx.V();

wsem.P();

}

SharedLock::ReleaseWrite() {

wsem.V();

wmx.P();

if (last writer)

rblock.V();

wmx.V();

}

This is a bit difficult to read, so let’s simplify it....