Function bufshutdown

freebsd/kern/vfs_bio.c:1336–1447

* Shutdown the system cleanly to prepare for reboot, halt, or power off. */

 * Shutdown the system cleanly to prepare for reboot, halt, or power off.
 */
void
bufshutdown(int show_busybufs)
{
	static int first_buf_printf = 1;
	struct buf *bp;
	int i, iter, nbusy, pbusy;
#ifndef PREEMPTION
	int subiter;
#endif

	/*
	 * Sync filesystems for shutdown
	 */
	wdog_kern_pat(WD_LASTVAL);
	kern_sync(curthread);

	/*
	 * With soft updates, some buffers that are
	 * written will be remarked as dirty until other
	 * buffers are written.
	 */
	for (iter = pbusy = 0; iter < 20; iter++) {
		nbusy = 0;
		for (i = nbuf - 1; i >= 0; i--) {
			bp = nbufp(i);
			if (isbufbusy(bp))
				nbusy++;
		}
		if (nbusy == 0) {
			if (first_buf_printf)
				printf("All buffers synced.");
			break;
		}
		if (first_buf_printf) {
			printf("Syncing disks, buffers remaining... ");
			first_buf_printf = 0;
		}
		printf("%d ", nbusy);
		if (nbusy < pbusy)
			iter = 0;
		pbusy = nbusy;

		wdog_kern_pat(WD_LASTVAL);
		kern_sync(curthread);

#ifdef PREEMPTION
		/*
		 * Spin for a while to allow interrupt threads to run.
		 */
		DELAY(50000 * iter);
#else
		/*
		 * Context switch several times to allow interrupt
		 * threads to run.
		 */
		for (subiter = 0; subiter < 50 * iter; subiter++) {
			thread_lock(curthread);
			mi_switch(SW_VOL);