IRQ blocking when reading audio CDs

From: Gundolf Kiefer
Date: Sun Sep 26 2004 - 07:11:04 EST


Dear Jens (& Christoph),

on my media PC (a Pentium II 350 MHz running Debian Woody with Kernel 2.4.25), I have problems using LIRC 0.6.6 with a serial IR reveiver when at the same time some application (cdparanoia, xmms/Audio CD reader) is reading audio data from a CD.

After some testing and exploration of the LIRC source code, I figured out that during audio CD reading interrupts seem to be blocked for a longer time (in the order of milliseconds), while lirc_serial measures the exact time between two serial interrupts and thus relies on an accurate timing. In consequence, LIRC does not recognize the IR sequences, there are no errors reported. Assigning a high priority to the serial interrupt using "irq_tune" did not help.

Is there a way to make the audio CD read operations less blocking? Or does any of you know a different source of the problem I observed?

Thank you very much,

Gundolf


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