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Modern CPUs are very fast, so why can\t I write a user mode interrupt handler?

April 26, 2017can''t CPUs fast handler interrupt mode Modern user write

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Modern CPUs are very fast, so why can\t I write a user mode interrupt handler?

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• (REG, quoting Pete Zaitcev) This is not a question of having enough CPU cycles to waste them on mode switches. Rather, the current Linux architecture does not allow it. User processes run with interrupts enabled. Thus, any interrupt handler must deactivate the particular interrupt source before a process is scheduled to run, or an interrupt storm results. The deactivation is done in a device specific manner, so at least a small device driver must be present in kernel mode.