Commit 587704ef authored by Alexander Gordeev's avatar Alexander Gordeev Committed by Vasily Gorbik
Browse files

s390/smp: do not preserve boot CPU lowcore on hotplug 



Once the kernel is running the boot CPU lowcore becomes
freeable and does not differ from the secondary CPU ones
in any way. Make use of it and do not preserve the boot
CPU lowcore on unplugging. That allows returning unused
memory when the boot CPU is offline and makes the code
more clear.

Signed-off-by: default avatarAlexander Gordeev <agordeev@linux.ibm.com>
Reviewed-by: default avatarHeiko Carstens <hca@linux.ibm.com>
Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
parent 57892847

arch/s390/kernel/smp.c

+18 −29
Original line number Diff line number Diff line
@@ -194,20 +194,12 @@ static int pcpu_alloc_lowcore(struct pcpu *pcpu, int cpu) 
	unsigned long async_stack, nodat_stack, mcck_stack;

	struct lowcore *lc;



	if (pcpu != &pcpu_devices[0]) {

		pcpu->lowcore =	(struct lowcore *)

			__get_free_pages(GFP_KERNEL | GFP_DMA, LC_ORDER);

	lc = (struct lowcore *) __get_free_pages(GFP_KERNEL | GFP_DMA, LC_ORDER);

	nodat_stack = __get_free_pages(GFP_KERNEL, THREAD_SIZE_ORDER);

		if (!pcpu->lowcore || !nodat_stack)

			goto out;

	} else {

		nodat_stack = pcpu->lowcore->nodat_stack - STACK_INIT_OFFSET;

	}

	async_stack = stack_alloc();

	mcck_stack = stack_alloc();

	if (!async_stack || !mcck_stack)

		goto out_stack;

	lc = pcpu->lowcore;

	if (!lc || !nodat_stack || !async_stack || !mcck_stack)

		goto out;

	memcpy(lc, &S390_lowcore, 512);

	memset((char *) lc + 512, 0, sizeof(*lc) - 512);

	lc->async_stack = async_stack + STACK_INIT_OFFSET;
@@ -220,40 +212,37 @@ static int pcpu_alloc_lowcore(struct pcpu *pcpu, int cpu) 
	lc->return_lpswe = gen_lpswe(__LC_RETURN_PSW);

	lc->return_mcck_lpswe = gen_lpswe(__LC_RETURN_MCCK_PSW);

	if (nmi_alloc_per_cpu(lc))

		goto out_stack;

		goto out;

	lowcore_ptr[cpu] = lc;

	pcpu->lowcore = lc;

	pcpu_sigp_retry(pcpu, SIGP_SET_PREFIX, (u32)(unsigned long) lc);

	return 0;



out_stack:

out:

	stack_free(mcck_stack);

	stack_free(async_stack);

out:

	if (pcpu != &pcpu_devices[0]) {

	free_pages(nodat_stack, THREAD_SIZE_ORDER);

		free_pages((unsigned long) pcpu->lowcore, LC_ORDER);

	}

	free_pages((unsigned long) lc, LC_ORDER);

	return -ENOMEM;

}



static void pcpu_free_lowcore(struct pcpu *pcpu)

{

	unsigned long async_stack, nodat_stack, mcck_stack, lowcore;



	nodat_stack = pcpu->lowcore->nodat_stack - STACK_INIT_OFFSET;

	async_stack = pcpu->lowcore->async_stack - STACK_INIT_OFFSET;

	mcck_stack = pcpu->lowcore->mcck_stack - STACK_INIT_OFFSET;

	lowcore = (unsigned long) pcpu->lowcore;

	unsigned long async_stack, nodat_stack, mcck_stack;

	struct lowcore *lc;



	lc = pcpu->lowcore;

	nodat_stack = lc->nodat_stack - STACK_INIT_OFFSET;

	async_stack = lc->async_stack - STACK_INIT_OFFSET;

	mcck_stack = lc->mcck_stack - STACK_INIT_OFFSET;

	pcpu_sigp_retry(pcpu, SIGP_SET_PREFIX, 0);

	lowcore_ptr[pcpu - pcpu_devices] = NULL;

	nmi_free_per_cpu(pcpu->lowcore);

	pcpu->lowcore = NULL;

	nmi_free_per_cpu(lc);

	stack_free(async_stack);

	stack_free(mcck_stack);

	if (pcpu == &pcpu_devices[0])

		return;

	free_pages(nodat_stack, THREAD_SIZE_ORDER);

	free_pages(lowcore, LC_ORDER);

	free_pages((unsigned long) lc, LC_ORDER);

}



static void pcpu_prepare_secondary(struct pcpu *pcpu, int cpu)