vi | Table of Contents
Char Device Registration 55
open and release 58
scull’s Memory Usage 60
read and write 63
Playing with the New Devices 70
Quick Reference 70
4. Debugging Techniques
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
73
Debugging Support in the Kernel 73
Debugging by Printing 75
Debugging by Querying 82
Debugging by Watching 91
Debugging System Faults 93
Debuggers and Related Tools 99
5. Concurrency and Race Conditions
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
106
Pitfalls in scull 107
Concurrency and Its Management 107
Semaphores and Mutexes 109
Completions 114
Spinlocks 116
Locking Traps 121
Alternatives to Locking 123
Quick Reference 130
6. Advanced Char Driver Operations
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
135
ioctl 135
Blocking I/O 147
poll and select 163
Asynchronous Notification 169
Seeking a Device 171
Access Control on a Device File 173
Quick Reference 179
7. Time, Delays, and Deferred Work
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
183
Measuring Time Lapses 183
Knowing the Current Time 188
Delaying Execution 190
Kernel Timers 196
Tasklets 202
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