Hi,
The comments surrounding free_irq() include these line:
* On a shared IRQ the caller must ensure the interrupt is disabled
* on the card it drives before calling this function. The function
* does not return until any executing interrupts for this IRQ
* have completed.
*
* This function may be called from interrupt context.
This last line is quite bogus.
- if we call this function to free IRQ "n" from an interrupt handler
running on IRQ "n", then we will deadlock; we call synchronize_irq(n)
which will wait for us to exit.
- if we call this function to free IRQ "n" from an interrupt handler
running on IRQ "b", and a handler for IRQ "n" is already running and
IRQ "n" interrupted IRQ "n", then we will deadlock.
In light of the above, I'd suggest changing the last line to:
* This function must not be called from interrupt context.
This patch is against 2.5.34:
--- orig/arch/i386/kernel/irq.c Fri Aug 30 14:52:51 2002
+++ linux/arch/i386/kernel/irq.c Sun Sep 29 14:13:39 2002
@@ -483,10 +483,7 @@
* does not return until any executing interrupts for this IRQ
* have completed.
*
- * This function may be called from interrupt context.
- *
- * Bugs: Attempting to free an irq in a handler for the same irq hangs
- * the machine.
+ * This function must not be called from interrupt context.
*/
void free_irq(unsigned int irq, void *dev_id)
--
Russell King ([email protected]) The developer of ARM Linux
http://www.arm.linux.org.uk/personal/aboutme.html