ksoftirqd_CPU0 using 99% CPU?

[Peep]

i can't figure out quite what this process is, but it seems to be using all my CPU cycles on my laptop whenever i'm connected to a particular wireless network using LEAP encryption. (cisco aironet 350). what is causing this and what can i do to keep it in check?

[chris z]

don't know if this helps, but i found this info doing a Google Search for ksoftirqd .

 

5.3 Softirq

 

When an IRQ comes, task switching is deferred until later to get better performance. Some Task jobs (that could have to be done just after the IRQ and that could take much CPU in interrupt time, like building up a TCP/IP packet) are queued and will be done at scheduling time (once a time-slice will end).

 

In recent kernels (2.4.x) the softirq mechanisms are given to a kernel_thread: ''ksoftirqd_CPUn''. n stands for the number of CPU executing kernel_thread (in a monoprocessor system ''ksoftirqd_CPU0'' uses PID 3).

 

Preparing Softirq

Enabling Softirq

 

''cpu_raise_softirq'' is a routine that will wake_up ''ksoftirqd_CPU0'' kernel thread, to let it manage the enqueued job.

 

|cpu_raise_softirq

  |__cpu_raise_softirq

  |wakeup_softirqd

     |wake_up_process

 

   * cpu_raise_softirq [kernel/softirq.c]

   * __cpu_raise_softirq [include/linux/interrupt.h]

   * wakeup_softirq [kernel/softirq.c]

   * wake_up_process [kernel/sched.c]

 

''__cpu_raise_softirq'' routine will set right bit in the vector describing softirq pending.

 

''wakeup_softirq'' uses ''wakeup_process'' to wake up ''ksoftirqd_CPU0'' kernel thread.

 

Executing Softirq

 

TODO: describing data structures involved in softirq mechanism.

 

When kernel thread ''ksoftirqd_CPU0'' has been woken up, it will execute queued jobs

 

The code of ''ksoftirqd_CPU0'' is (main endless loop):

 

for (;;) {

  if (!softirq_pending(cpu))  

     schedule();

     __set_current_state(TASK_RUNNING);

  while (softirq_pending(cpu)) {  

     do_softirq();  

     if (current->need_resched)  

        schedule  

  }

  __set_current_state(TASK_INTERRUPTIBLE)

}

 

   * ksoftirqd [kernel/softirq.c]

 

Chris