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

From: Robert Jennings <[email-masked]>
Date: Wed, 1 May 2013 19:39:00 -0500

* Benjamin Herrenschmidt ([email-masked]) wrote:
> On Wed, 2013-05-01 at 10:25 -0500, Nathan Fontenot wrote:
> > On 04/26/2013 04:32 PM, 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).
> > > 
> > 
> > This fixes a long standing bug in partition migration.
> > 
> > Acked-by: Nathan Fontenot <[email-masked]>
> 
> I was about to apply this one but had to take it out of my branch as it
> breaks the UP build. Can you send a new revision of the patch ? It's a
> bug fix, I'll put it in at -rc1.

Yes, sorry.  I'll get you a fix for the -rc1 timeframe for sure.

> Cheers,
> Ben.
> 
> > > Cc: <[email-masked]>
> > > Signed-off-by: Robert Jennings <[email-masked]>
> > > ---
> > >  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;
> > >  }
> > >  
> > 
> > 
> 
> 
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