Subject: Re: [PATCH] powerpc: Bring all threads online prior to migration/hibernation

From: "Srivatsa S. Bhat" <[email-masked]>
Date: Thu, 02 May 2013 01:13:43 +0530

On 04/27/2013 03:02 AM, Robert Jennings wrote:
> With this patch before a migration/hibernation all threads present but
> not online will be brought online.  After migration/hibernation those
> threads are taken back offline.
> 
> During migration/hibernation all online CPUs must call H_JOIN, this is
> required by the hypervisor.  Without this patch, threads that are offline
> (H_CEDE'd) will not be woken to make the H_JOIN call and the OS will be
> deadlocked (all threads either JOIN'd or CEDE'd).
> 
> Cc: <[email-masked]>
> Signed-off-by: Robert Jennings <[email-masked]>
> ---

Reviewed-by: Srivatsa S. Bhat <[email-masked]>

Regards,
Srivatsa S. Bhat

>  arch/powerpc/include/asm/rtas.h          |    2 +
>  arch/powerpc/kernel/rtas.c               |   95 ++++++++++++++++++++++++++++++
>  arch/powerpc/platforms/pseries/suspend.c |   22 +++++++
>  3 files changed, 119 insertions(+)
> 
> diff --git a/arch/powerpc/include/asm/rtas.h b/arch/powerpc/include/asm/rtas.h
> index aef00c6..ee38f29 100644
> --- a/arch/powerpc/include/asm/rtas.h
> +++ b/arch/powerpc/include/asm/rtas.h
> @@ -262,6 +262,8 @@ extern void rtas_progress(char *s, unsigned short hex);
>  extern void rtas_initialize(void);
>  extern int rtas_suspend_cpu(struct rtas_suspend_me_data *data);
>  extern int rtas_suspend_last_cpu(struct rtas_suspend_me_data *data);
> +extern int rtas_online_cpus_mask(cpumask_var_t cpus);
> +extern int rtas_offline_cpus_mask(cpumask_var_t cpus);
>  extern int rtas_ibm_suspend_me(struct rtas_args *);
> 
>  struct rtc_time;
> diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
> index 1fd6e7b..855ee98 100644
> --- a/arch/powerpc/kernel/rtas.c
> +++ b/arch/powerpc/kernel/rtas.c
> @@ -19,6 +19,7 @@
>  #include <linux/init.h>
>  #include <linux/capability.h>
>  #include <linux/delay.h>
> +#include <linux/cpu.h>
>  #include <linux/smp.h>
>  #include <linux/completion.h>
>  #include <linux/cpumask.h>
> @@ -807,6 +808,77 @@ static void rtas_percpu_suspend_me(void *info)
>  	__rtas_suspend_cpu((struct rtas_suspend_me_data *)info, 1);
>  }
> 
> +enum rtas_cpu_state {
> +	DOWN,
> +	UP,
> +};
> +
> +/* On return cpumask will be altered to indicate CPUs changed */
> +static int rtas_cpu_state_change_mask(enum rtas_cpu_state state,
> +				cpumask_var_t cpus)
> +{
> +	int cpu;
> +	int cpuret = 0;
> +	int ret = 0;
> +
> +	if (cpumask_empty(cpus))
> +		return 0;
> +
> +	for_each_cpu(cpu, cpus) {
> +		switch (state) {
> +		case DOWN:
> +			cpuret = cpu_down(cpu);
> +			break;
> +		case UP:
> +			cpuret = cpu_up(cpu);
> +			break;
> +		}
> +		if (cpuret) {
> +			pr_debug("%s: cpu_%s for cpu#%d returned %d.\n",
> +					__func__,
> +					((state == UP) ? "up" : "down"),
> +					cpu, cpuret);
> +			if (!ret)
> +				ret = cpuret;
> +			if (state == UP) {
> +				cpumask_shift_right(cpus, cpus, cpu);
> +				cpumask_shift_left(cpus, cpus, cpu);
> +				break;
> +			} else
> +				cpumask_clear_cpu(cpu, cpus);
> +		}
> +	}
> +
> +	return ret;
> +}
> +
> +int rtas_online_cpus_mask(cpumask_var_t cpus)
> +{
> +	int ret;
> +
> +	ret = rtas_cpu_state_change_mask(UP, cpus);
> +
> +	if (ret) {
> +		cpumask_var_t tmp_mask;
> +
> +		if (!alloc_cpumask_var(&tmp_mask, GFP_TEMPORARY))
> +			return ret;
> +
> +		cpumask_copy(tmp_mask, cpus);
> +		rtas_offline_cpus_mask(tmp_mask);
> +		free_cpumask_var(tmp_mask);
> +	}
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL(rtas_online_cpus_mask);
> +
> +int rtas_offline_cpus_mask(cpumask_var_t cpus)
> +{
> +	return rtas_cpu_state_change_mask(DOWN, cpus);
> +}
> +EXPORT_SYMBOL(rtas_offline_cpus_mask);
> +
>  int rtas_ibm_suspend_me(struct rtas_args *args)
>  {
>  	long state;
> @@ -814,6 +886,8 @@ int rtas_ibm_suspend_me(struct rtas_args *args)
>  	unsigned long retbuf[PLPAR_HCALL_BUFSIZE];
>  	struct rtas_suspend_me_data data;
>  	DECLARE_COMPLETION_ONSTACK(done);
> +	cpumask_var_t offline_mask;
> +	int cpuret;
> 
>  	if (!rtas_service_present("ibm,suspend-me"))
>  		return -ENOSYS;
> @@ -837,11 +911,24 @@ int rtas_ibm_suspend_me(struct rtas_args *args)
>  		return 0;
>  	}
> 
> +	if (!alloc_cpumask_var(&offline_mask, GFP_TEMPORARY))
> +		return -ENOMEM;
> +
>  	atomic_set(&data.working, 0);
>  	atomic_set(&data.done, 0);
>  	atomic_set(&data.error, 0);
>  	data.token = rtas_token("ibm,suspend-me");
>  	data.complete = &done;
> +
> +	/* All present CPUs must be online */
> +	cpumask_andnot(offline_mask, cpu_present_mask, cpu_online_mask);
> +	cpuret = rtas_online_cpus_mask(offline_mask);
> +	if (cpuret) {
> +		pr_err("%s: Could not bring present CPUs online.\n", __func__);
> +		atomic_set(&data.error, cpuret);
> +		goto out;
> +	}
> +
>  	stop_topology_update();
> 
>  	/* Call function on all CPUs.  One of us will make the
> @@ -857,6 +944,14 @@ int rtas_ibm_suspend_me(struct rtas_args *args)
> 
>  	start_topology_update();
> 
> +	/* Take down CPUs not online prior to suspend */
> +	cpuret = rtas_offline_cpus_mask(offline_mask);
> +	if (cpuret)
> +		pr_warn("%s: Could not restore CPUs to offline state.\n",
> +				__func__);
> +
> +out:
> +	free_cpumask_var(offline_mask);
>  	return atomic_read(&data.error);
>  }
>  #else /* CONFIG_PPC_PSERIES */
> diff --git a/arch/powerpc/platforms/pseries/suspend.c b/arch/powerpc/platforms/pseries/suspend.c
> index 47226e0..5f997e7 100644
> --- a/arch/powerpc/platforms/pseries/suspend.c
> +++ b/arch/powerpc/platforms/pseries/suspend.c
> @@ -16,6 +16,7 @@
>    * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
>    */
> 
> +#include <linux/cpu.h>
>  #include <linux/delay.h>
>  #include <linux/suspend.h>
>  #include <linux/stat.h>
> @@ -126,11 +127,15 @@ static ssize_t store_hibernate(struct device *dev,
>  			       struct device_attribute *attr,
>  			       const char *buf, size_t count)
>  {
> +	cpumask_var_t offline_mask;
>  	int rc;
> 
>  	if (!capable(CAP_SYS_ADMIN))
>  		return -EPERM;
> 
> +	if (!alloc_cpumask_var(&offline_mask, GFP_TEMPORARY))
> +		return -ENOMEM;
> +
>  	stream_id = simple_strtoul(buf, NULL, 16);
> 
>  	do {
> @@ -140,15 +145,32 @@ static ssize_t store_hibernate(struct device *dev,
>  	} while (rc == -EAGAIN);
> 
>  	if (!rc) {
> +		/* All present CPUs must be online */
> +		cpumask_andnot(offline_mask, cpu_present_mask,
> +				cpu_online_mask);
> +		rc = rtas_online_cpus_mask(offline_mask);
> +		if (rc) {
> +			pr_err("%s: Could not bring present CPUs online.\n",
> +					__func__);
> +			goto out;
> +		}
> +
>  		stop_topology_update();
>  		rc = pm_suspend(PM_SUSPEND_MEM);
>  		start_topology_update();
> +
> +		/* Take down CPUs not online prior to suspend */
> +		if (!rtas_offline_cpus_mask(offline_mask))
> +			pr_warn("%s: Could not restore CPUs to offline "
> +					"state.\n", __func__);
>  	}
> 
>  	stream_id = 0;
> 
>  	if (!rc)
>  		rc = count;
> +out:
> +	free_cpumask_var(offline_mask);
>  	return rc;
>  }
>