bcm: fix mysterious core clock resets under SMP (thanks richard miller)

reference: https://github.com/raspberrypi/firmware/issues/542

procsave(Proc* p)
{
	uvlong t;

	cycles(&t);
	p->pcycles += t;

// TODO: save and restore VFPv3 FP state once 5[cal] know the new registers.
	fpuprocsave(p);
	/*
	 * Prevent the following scenario:
	 *	pX sleeps on cpuA, leaving its page tables in mmul1
	 *	pX wakes up on cpuB, and exits, freeing its page tables
	 *  pY on cpuB allocates a freed page table page and overwrites with data
	 *  cpuA takes an interrupt, and is now running with bad page tables
	 * In theory this shouldn't hurt because only user address space tables
	 * are affected, and mmuswitch will clear mmul1 before a user process is
	 * dispatched.  But empirically it correlates with weird problems, eg
	 * resetting of the core clock at 0x4000001C which confuses local timers.
	 */
	if(conf.nmach > 1)
		mmuswitch(nil);
}

0 files changed, 0 insertions, 0 deletions