ARM: 7759/1: decouple CPU offlining from reboot/shutdown

Add comments to machine_shutdown()/halt()/power_off()/restart() that
describe their purpose and/or requirements re: CPUs being active/not.

In machine_shutdown(), replace the call to smp_send_stop() with a call to
disable_nonboot_cpus(). This completely disables all but one CPU, thus
satisfying the requirement that only a single CPU be active for kexec.
Adjust Kconfig dependencies for this change.

In machine_halt()/power_off()/restart(), call smp_send_stop() directly,
rather than via machine_shutdown(); these functions don't need to
completely de-activate all CPUs using hotplug, but rather just quiesce
them.

Remove smp_kill_cpus(), and its call from smp_send_stop().
smp_kill_cpus() was indirectly calling smp_ops.cpu_kill() without calling
smp_ops.cpu_die() on the target CPUs first. At least some implementations
of smp_ops had issues with this; it caused cpu_kill() to hang on Tegra,
for example. Since smp_send_stop() is only used for shutdown, halt, and
power-off, there is no need to attempt any kind of CPU hotplug here.

Adjust Kconfig to reflect that machine_shutdown() (and hence kexec)
relies upon disable_nonboot_cpus(). However, this alone doesn't guarantee
that hotplug will work, or even that hotplug is implemented for a
particular piece of HW that a multi-platform zImage runs on. Hence, add
error-checking to machine_kexec() to determine whether it did work.

Suggested-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Tested-by:  Zhangfei Gao <zhangfei.gao@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Stephen Warren 2013-06-14 16:14:14 +01:00 committed by Russell King
parent 69f91ff8c9
commit 19ab428f4b
4 changed files with 42 additions and 20 deletions

View File

@ -2016,7 +2016,7 @@ config XIP_PHYS_ADDR
config KEXEC
bool "Kexec system call (EXPERIMENTAL)"
depends on (!SMP || HOTPLUG_CPU)
depends on (!SMP || PM_SLEEP_SMP)
help
kexec is a system call that implements the ability to shutdown your
current kernel, and to start another kernel. It is like a reboot

View File

@ -134,6 +134,10 @@ void machine_kexec(struct kimage *image)
unsigned long reboot_code_buffer_phys;
void *reboot_code_buffer;
if (num_online_cpus() > 1) {
pr_err("kexec: error: multiple CPUs still online\n");
return;
}
page_list = image->head & PAGE_MASK;

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@ -184,30 +184,61 @@ int __init reboot_setup(char *str)
__setup("reboot=", reboot_setup);
/*
* Called by kexec, immediately prior to machine_kexec().
*
* This must completely disable all secondary CPUs; simply causing those CPUs
* to execute e.g. a RAM-based pin loop is not sufficient. This allows the
* kexec'd kernel to use any and all RAM as it sees fit, without having to
* avoid any code or data used by any SW CPU pin loop. The CPU hotplug
* functionality embodied in disable_nonboot_cpus() to achieve this.
*/
void machine_shutdown(void)
{
#ifdef CONFIG_SMP
smp_send_stop();
#endif
disable_nonboot_cpus();
}
/*
* Halting simply requires that the secondary CPUs stop performing any
* activity (executing tasks, handling interrupts). smp_send_stop()
* achieves this.
*/
void machine_halt(void)
{
machine_shutdown();
smp_send_stop();
local_irq_disable();
while (1);
}
/*
* Power-off simply requires that the secondary CPUs stop performing any
* activity (executing tasks, handling interrupts). smp_send_stop()
* achieves this. When the system power is turned off, it will take all CPUs
* with it.
*/
void machine_power_off(void)
{
machine_shutdown();
smp_send_stop();
if (pm_power_off)
pm_power_off();
}
/*
* Restart requires that the secondary CPUs stop performing any activity
* while the primary CPU resets the system. Systems with a single CPU can
* use soft_restart() as their machine descriptor's .restart hook, since that
* will cause the only available CPU to reset. Systems with multiple CPUs must
* provide a HW restart implementation, to ensure that all CPUs reset at once.
* This is required so that any code running after reset on the primary CPU
* doesn't have to co-ordinate with other CPUs to ensure they aren't still
* executing pre-reset code, and using RAM that the primary CPU's code wishes
* to use. Implementing such co-ordination would be essentially impossible.
*/
void machine_restart(char *cmd)
{
machine_shutdown();
smp_send_stop();
arm_pm_restart(reboot_mode, cmd);

View File

@ -651,17 +651,6 @@ void smp_send_reschedule(int cpu)
smp_cross_call(cpumask_of(cpu), IPI_RESCHEDULE);
}
#ifdef CONFIG_HOTPLUG_CPU
static void smp_kill_cpus(cpumask_t *mask)
{
unsigned int cpu;
for_each_cpu(cpu, mask)
platform_cpu_kill(cpu);
}
#else
static void smp_kill_cpus(cpumask_t *mask) { }
#endif
void smp_send_stop(void)
{
unsigned long timeout;
@ -679,8 +668,6 @@ void smp_send_stop(void)
if (num_online_cpus() > 1)
pr_warning("SMP: failed to stop secondary CPUs\n");
smp_kill_cpus(&mask);
}
/*