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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: Max Filippov <jcmvbkbc@gmail.com>
This commit is contained in:
Max Filippov 2018-12-21 08:26:20 -08:00
parent 4fe8713b87
commit 32a7726c4f
2 changed files with 25 additions and 14 deletions
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5
arch/xtensa/kernel/head.S
View File

@ -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

30
arch/xtensa/kernel/smp.c
View File

@ -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;
}