[$] Software interrupts and realtime
The Linux kernel's software interrupt ("softirq") mechanism is a bit of a
strange beast. It is an obscure holdover from the earliest days of Linux
and a mechanism that few kernel developers ever deal with directly. Yet it
is at the core of much of the kernel's most important processing.
Occasionally softirqs make their presence known in undesired ways; it is
not surprising that the kernel's frequent problem child — the realtime
preemption patch set — has often run afoul of them. Recent versions of
that patch set embody a new approach to the software interrupt problem that
merits a look.