> I have a very basic doubt here ... what makes it impossible to sleep
> in an ISR? I mean, I know that the kernel preemption is disabled and
> the kernel will panic, but I could not understand why?
Because the interrupt which you are serving in the
ISR has been masked to avoid preemption(
true for maskable inetrrupts ).Any locks you are holding in ISR are now with
you solely. So, if you try to sleep you take the locks you untill you are
rescheduled and complete. This may lead to
a deadlock for the lock resource.
Ok, but how about an ISR, that does not take any locks? Why can't we
sleep in SUCH an ISR?
AFAIK, taking a lock disables kernel preemption, and hence it is not
allowed to sleep. So I think my question would boil down to why is
sleeping not allowed when the kernel preemption is disabled.
LL
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