Commit ce024192 authored by Andrew Jones's avatar Andrew Jones Committed by Radim Krčmář
Browse files

arm/arm64: smp: cpu0 is special

Unless cpu0 code explicitly calls do_idle(), then it never will,
and thus any on_cpu(0, ...) calls will hang. Let's assume that
if cpu0 hasn't already called do_idle() that the on_cpu(0, ...)
call from a secondary CPU was a programming error and assert.
However, it's possible the developer intends cpu0 to call do_idle
later, so give the developer a chance to disable the assert too.

Also, while cpu0 is special, it's not that special. It shouldn't
be the only CPU that can call on_cpus().

Finally, let's not mess with cpu0's idle state in on_cpus(), as
this could potentially confuse another CPU that's checking it.
Signed-off-by: Andrew Jones's avatarAndrew Jones <>
Signed-off-by: default avatarRadim Krčmář <>
parent eaa04bc8
......@@ -10,6 +10,8 @@
#define smp_processor_id() (current_thread_info()->cpu)
extern bool cpu0_calls_idle;
extern void halt(void);
extern void do_idle(void);
......@@ -14,6 +14,8 @@
#include <asm/psci.h>
#include <asm/smp.h>
bool cpu0_calls_idle;
cpumask_t cpu_present_mask;
cpumask_t cpu_online_mask;
cpumask_t cpu_idle_mask;
......@@ -81,6 +83,9 @@ void do_idle(void)
int cpu = smp_processor_id();
if (cpu == 0)
cpu0_calls_idle = true;
set_cpu_idle(cpu, true);
......@@ -103,6 +108,9 @@ void on_cpu_async(int cpu, void (*func)(void *data), void *data)
assert_msg(cpu != 0 || cpu0_calls_idle, "Waiting on CPU0, which is unlikely to idle. "
"If this is intended set cpu0_calls_idle=1");
if (!cpu_online(cpu))
__smp_boot_secondary(cpu, do_idle);
......@@ -133,17 +141,15 @@ void on_cpu(int cpu, void (*func)(void *data), void *data)
void on_cpus(void (*func)(void))
int cpu;
int cpu, me = smp_processor_id();
for_each_present_cpu(cpu) {
if (cpu == 0)
if (cpu == me)
on_cpu_async(cpu, (on_cpu_func)func, NULL);
set_cpu_idle(0, true);
while (!cpumask_full(&cpu_idle_mask))
while (cpumask_weight(&cpu_idle_mask) < nr_cpus - 1)
set_cpu_idle(0, false);
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