安徽理工大学2014操作系统B卷答案,及试题(上张)

signal(S);

perform read operation; wait(rmutex); readcount=readcount-1; if readcount==0 then signal(wmutex); signal(rmutex); until false; end; writer：begin repeat wait(mutex); if writecount==0

2.

then wait(S);

writecount=writecount+1; signal(mutex); wait(wmutex);

perform write operation; signal(wmutex); wait(mutex);

writecount=writecount-1; if writecount==0 then signal(S); signal(mutex); until false; end;

得出安全序列为P4->P2->P3->P5->P1