Commit 32a7726c authored by Max Filippov's avatar Max Filippov
Browse files

xtensa: SMP: fix secondary CPU initialization 



- add missing memory barriers to the secondary CPU synchronization spin
  loops; add comment to the matching memory barrier in the boot_secondary
  and __cpu_die functions;
- use READ_ONCE/WRITE_ONCE to access cpu_start_id/cpu_start_ccount
  instead of reading/writing them directly;
- re-initialize cpu_running every time before starting secondary CPU to
  flush possible previous CPU startup results.

Signed-off-by: default avatarMax Filippov <jcmvbkbc@gmail.com>
parent 4fe8713b

arch/xtensa/kernel/head.S

+4 −1
Original line number Diff line number Diff line
@@ -276,12 +276,13 @@ should_never_return: 


	movi	a2, cpu_start_ccount

1:

	memw

	l32i	a3, a2, 0

	beqi	a3, 0, 1b

	movi	a3, 0

	s32i	a3, a2, 0

	memw

1:

	memw

	l32i	a3, a2, 0

	beqi	a3, 0, 1b

	wsr	a3, ccount
@@ -317,11 +318,13 @@ ENTRY(cpu_restart) 
	rsr	a0, prid

	neg	a2, a0

	movi	a3, cpu_start_id

	memw

	s32i	a2, a3, 0

#if XCHAL_DCACHE_IS_WRITEBACK

	dhwbi	a3, 0

#endif

1:

	memw

	l32i	a2, a3, 0

	dhi	a3, 0

	bne	a2, a0, 1b

arch/xtensa/kernel/smp.c

+21 −13
Original line number Diff line number Diff line
@@ -195,9 +195,11 @@ static int boot_secondary(unsigned int cpu, struct task_struct *ts) 
	int i;



#ifdef CONFIG_HOTPLUG_CPU

	cpu_start_id = cpu;

	system_flush_invalidate_dcache_range(

			(unsigned long)&cpu_start_id, sizeof(cpu_start_id));

	WRITE_ONCE(cpu_start_id, cpu);

	/* Pairs with the third memw in the cpu_restart */

	mb();

	system_flush_invalidate_dcache_range((unsigned long)&cpu_start_id,

					     sizeof(cpu_start_id));

#endif

	smp_call_function_single(0, mx_cpu_start, (void *)cpu, 1);
@@ -206,18 +208,21 @@ static int boot_secondary(unsigned int cpu, struct task_struct *ts) 
			ccount = get_ccount();

		while (!ccount);



		cpu_start_ccount = ccount;

		WRITE_ONCE(cpu_start_ccount, ccount);



		while (time_before(jiffies, timeout)) {

		do {

			/*

			 * Pairs with the first two memws in the

			 * .Lboot_secondary.

			 */

			mb();

			if (!cpu_start_ccount)

				break;

		}

			ccount = READ_ONCE(cpu_start_ccount);

		} while (ccount && time_before(jiffies, timeout));



		if (cpu_start_ccount) {

		if (ccount) {

			smp_call_function_single(0, mx_cpu_stop,

						 (void *)cpu, 1);

			cpu_start_ccount = 0;

			WRITE_ONCE(cpu_start_ccount, 0);

			return -EIO;

		}

	}
@@ -237,6 +242,7 @@ int __cpu_up(unsigned int cpu, struct task_struct *idle) 
	pr_debug("%s: Calling wakeup_secondary(cpu:%d, idle:%p, sp: %08lx)\n",

			__func__, cpu, idle, start_info.stack);



	init_completion(&cpu_running);

	ret = boot_secondary(cpu, idle);

	if (ret == 0) {

		wait_for_completion_timeout(&cpu_running,
@@ -299,7 +305,9 @@ void __cpu_die(unsigned int cpu) 
	while (time_before(jiffies, timeout)) {

		system_invalidate_dcache_range((unsigned long)&cpu_start_id,

					       sizeof(cpu_start_id));

		if (cpu_start_id == -cpu) {

		/* Pairs with the second memw in the cpu_restart */

		mb();

		if (READ_ONCE(cpu_start_id) == -cpu) {

			platform_cpu_kill(cpu);

			return;

		}

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