Working with the Unix OS

Figure 27. Driver Entry Points........................................................................................... 143
Figure 28. Block and Character Device Switch Tables....................................................... 143
Figure 29. Opening a Device ............................................................................................. 144
Figure 30. Closing a Device .............................................................................................. 144
Figure 31. Reading Disk Data - block & raw interface....................................................... 145
Figure 32. Data Sequence and Data Flow through Line Dicsipline..................................... 146
Figure 33. Removing characters from a Clist ..................................................................... 147
Figure 34. Placing characters on a Clist ............................................................................. 147
Figure 35. Writing Data to a Terminal ............................................................................... 148
Figure 36. Flooding Standard Output with Data................................................................. 148
Figure 37. Algorithm for Reading a Terminal ........................................................................1
Figure 38. Contending for Terminal Input Data ................................................................. 149
Figure 39. Raw Mode - Reading 5 character Bursts ........................................................... 150
Figure 40. Polling a Terminal ............................................................................................ 150
Figure 41. Loggin in.......................................................................................................... 151
Figure 42. A Stream after Open......................................................................................... 151
Figure 43. Pushing a Module onto a Stream....................................................................... 152
Figure 44. Windowing VT................................................................................................. 152
Figure 45. Pseudo-code for Multiplexing Windows ........................................................... 152
Figure 46. Process Scheduling........................................................................................... 170
Figure 47. Range of Process Priorities ............................................................................... 171
Figure 48. Process Scheduling Example ............................................................................ 171
Figure 49. Tie breaker rule ................................................................................................ 173
Figure 50. Fair Share Scheduler......................................................................................... 173
Figure 51. Program Using Timer ....................................................................................... 174
Figure 52. Alarm Call........................................................................................................ 174
Figure 53. Clock Handler .................................................................................................. 175
Figure 54. Invoking Profil system call ............................................................................... 175
Figure 55. Output for Profil Program................................................................................. 175
Figure 56. Algorithm for Allocating Space from Maps ...................................................... 176
Figure 57. Mapping Process Space .................................................................................... 177
Figure 58. Swapping a Process into Memory ..................................................................... 177
Figure 59. Adjusting Memory Map for Expansion Swap.................................................... 177
Figure 60. Algorithm for Swapper ..................................................................................... 178
Figure 61. Thrashing due to Swapping............................................................................... 179
Figure 62. Sequence of Swapping Operations.................................................................... 179
Figure 63. Free List of Buffers .......................................................................................... 180
Figure 64. Buffers on the Hash Queues.............................................................................. 181
Figure 65. Algorithm for Buffer Allocation ....................................................................... 181
Figure 66. First Scenario in Finding a Buffer: Buffer on Hash Queue................................. 182
Figure 67. Second Scenario for Buffer Allocation.............................................................. 183
Figure 68. Third Scenario for Buffer Allocation................................................................ 183
Figure 69. Forth Scenario for Buffer Allocation................................................................. 184
Figure 70. Race for Free Buffer ......................................................................................... 184
Figure 71. Fifth Scenario for Buffer Allocation.................................................................. 184
Figure 72. Race for a Locked Buffer.................................................................................. 185
Figure 73. Reading a Disk Block Bach, "bread"................................................................. 185
Figure 74. Algorithm for Block Read Ahead "breada".................................................... 186
Figure 75. Writing a Disk Block Bach, "bwrite". ........................................................... 186