Книга: Embedded Linux Primer: A Practical, Real-World Approach

17.4.2. Preemption Debugging

17.4.2. Preemption Debugging

To enable preemption debugging, enable CONFIG_DEBUG_PREEMPT in the kernel configuration. This debug feature enables the detection of unsafe use of preemption semantics such as preemption count underflows and attempts to sleep while in an invalid context. To use it, simply enable the feature and watch for any reports on the console or system log. Here is just a small sample of reports possible when preemption debugging is enabled:

BUG: <me> <mypid>, possible wake_up race on <proc> <pid>

BUG: lock recursion deadlock detected! <more info>

BUG: nonzero lock count <n> at exit time?

Many more messages are possiblethese are just a few examples of the kinds of problems that can be detected. These messages will help you avoid deadlocks and other erroneous or dangerous programming semantics when using real-time kernel features. For more details on the messages and conditions under which they are emitted, browse the Linux kernel source file .../kernel/rt-debug.c.

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