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| FreeBSD 5 内核源代码分析之中断处理 |
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mtx_unlock_spin(&sched_lock); } } |
3,软件中断swi
我们将举例说明软件中断swi。
3.1登记
系统启动时，调用start_softintr()登记两个重要的软件中断，
软时钟中断和VM软中断。
当情况需要时，内核将调用swi_sched()来调度软件中断的运行。
| 代码: |
/* * Start standard software interrupt threads */ static void start_softintr(void *dummy) { struct proc *p; if (swi_add(&clk_ithd, "clock", softclock, NULL, SWI_CLOCK, INTR_MPSAFE, &softclock_ih) || swi_add(NULL, "vm", swi_vm, NULL, SWI_VM, INTR_MPSAFE, &vm_ih)) panic("died while creating standard software ithreads"); p = clk_ithd->it_td->td_proc; PROC_LOCK(p); p->p_flag |= P_NOLOAD; PROC_UNLOCK(p); } int swi_add(struct ithd **ithdp, const char *name, driver_intr_t handler, void *arg, int pri, enum intr_type flags, void **cookiep) { struct ithd *ithd; int error; if (flags & (INTR_FAST | INTR_ENTROPY)) return (EINVAL); ithd = (ithdp != NULL) ? *ithdp : NULL; if (ithd != NULL) { if ((ithd->it_flags & IT_SOFT) == 0) return(EINVAL); } else { error = ithread_create(&ithd, pri, IT_SOFT, NULL, NULL, "swi%d:", pri); if (error) return (error); if (ithdp != NULL) *ithdp = ithd; } return (ithread_add_handler(ithd, name, handler, arg, (pri * RQ_PPQ) + PI_SOFT, flags, cookiep)); } |
3.2调度
硬件时钟中断，需要处理非紧急时钟事务时，调度softclock，以便在响应完硬件时钟中断后
运行softclock。
| 代码: |
/* * The real-time timer, interrupting hz times per second. */ void hardclock(frame) register struct clockframe *frame; { ...... if (need_softclock) swi_sched(softclock_ih, 0); ...... } /* * Schedule a heavyweight software interrupt process. */ void swi_sched(void *cookie, int flags) { struct intrhand *ih = (struct intrhand *)cookie; struct ithd *it = ih->ih_ithread; int error; atomic_add_int(&cnt.v_intr, 1); /* one more global interrupt */ CTR3(KTR_INTR, "swi_sched pid %d(%s) need=%d", it->it_td->td_proc->p_pid, it->it_td->td_proc->p_comm, it->it_need); /* * Set ih_need for this handler so that if the ithread is already * running it will execute this handler on the next pass. Otherwise, * it will execute it the next time it runs. */ atomic_store_rel_int(&ih->ih_need, 1); if (!(flags & SWI_DELAY)) { error = ithread_schedule(it, !cold && !dumping); KASSERT(error == 0, ("stray software interrupt")); } } |
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