CODEWITHSUNDEEP
linux-kernellinux-device-driver
Vinayak Kolagi
Vinayak Kolagi

Reputation: 1881

Restriction on interrupt routines in linux kernel drivers

Every device driver book talks about not using functions that sleep in interrupt routines. What issues occur by calling these functions from ISRs ?

Upvotes: 0

Views: 180

Answers (1)

Milan
Milan

Reputation: 15849

A total lockdown of the kernel is the issue here. The kernel is in interrupt context when executing interrupt handlers, that is, the interrupt handler is not associated with any process (the current macro cannot be used).

If you are able to sleep, you would never be able to get back to the interrupted code, since the scheduler would not know how to get back to it.

Holding a lock in the interrupt handler, and then sleeping, allowing another process to run and then entering the interrupt handler again and trying to re-acquire the lock would deadlock the kernel.

If you try to read more about how the scheduling in the kernel works, you will soon realize why sleeping is a no go in certain contexts.

Upvotes: 2

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