Patchwork [v5,29/45] x86/xen: Use get/put_online_cpus_atomic() to prevent CPU offline

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Submitter Srivatsa S. Bhat
Date Jan. 22, 2013, 7:40 a.m.
Message ID <20130122074046.13822.61950.stgit@srivatsabhat.in.ibm.com>
Download mbox | patch
Permalink /patch/214431/
State Not Applicable
Headers show

Comments

Srivatsa S. Bhat - Jan. 22, 2013, 7:40 a.m.
Once stop_machine() is gone from the CPU offline path, we won't be able to
depend on preempt_disable() or local_irq_disable() to prevent CPUs from
going offline from under us.

Use the get/put_online_cpus_atomic() APIs to prevent CPUs from going offline,
while invoking from atomic context.

Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Cc: xen-devel@lists.xensource.com
Cc: virtualization@lists.linux-foundation.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---

 arch/x86/xen/mmu.c |   11 +++++++++--
 arch/x86/xen/smp.c |    9 +++++++++
 2 files changed, 18 insertions(+), 2 deletions(-)
Konrad Rzeszutek Wilk - Feb. 19, 2013, 6:10 p.m.
On Tue, Jan 22, 2013 at 01:10:51PM +0530, Srivatsa S. Bhat wrote:
> Once stop_machine() is gone from the CPU offline path, we won't be able to
> depend on preempt_disable() or local_irq_disable() to prevent CPUs from
> going offline from under us.
> 
> Use the get/put_online_cpus_atomic() APIs to prevent CPUs from going offline,
> while invoking from atomic context.
> 
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

Weird. I see this in the patch but I don't see it in the header? Did you
explicitly suppress the CC part?


Anyhow, the patch looks sane enough, thought I need to to run it through
a test framework just to be on a sure side.

> Cc: Jeremy Fitzhardinge <jeremy@goop.org>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: x86@kernel.org
> Cc: xen-devel@lists.xensource.com
> Cc: virtualization@lists.linux-foundation.org
> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
> ---
> 
>  arch/x86/xen/mmu.c |   11 +++++++++--
>  arch/x86/xen/smp.c |    9 +++++++++
>  2 files changed, 18 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
> index 01de35c..6a95a15 100644
> --- a/arch/x86/xen/mmu.c
> +++ b/arch/x86/xen/mmu.c
> @@ -39,6 +39,7 @@
>   * Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007
>   */
>  #include <linux/sched.h>
> +#include <linux/cpu.h>
>  #include <linux/highmem.h>
>  #include <linux/debugfs.h>
>  #include <linux/bug.h>
> @@ -1163,9 +1164,13 @@ static void xen_drop_mm_ref(struct mm_struct *mm)
>   */
>  static void xen_exit_mmap(struct mm_struct *mm)
>  {
> -	get_cpu();		/* make sure we don't move around */
> +	/*
> +	 * Make sure we don't move around, and prevent CPUs from going
> +	 * offline.
> +	 */
> +	get_online_cpus_atomic();
>  	xen_drop_mm_ref(mm);
> -	put_cpu();
> +	put_online_cpus_atomic();
>  
>  	spin_lock(&mm->page_table_lock);
>  
> @@ -1371,6 +1376,7 @@ static void xen_flush_tlb_others(const struct cpumask *cpus,
>  	args->op.arg2.vcpumask = to_cpumask(args->mask);
>  
>  	/* Remove us, and any offline CPUS. */
> +	get_online_cpus_atomic();
>  	cpumask_and(to_cpumask(args->mask), cpus, cpu_online_mask);
>  	cpumask_clear_cpu(smp_processor_id(), to_cpumask(args->mask));
>  
> @@ -1383,6 +1389,7 @@ static void xen_flush_tlb_others(const struct cpumask *cpus,
>  	MULTI_mmuext_op(mcs.mc, &args->op, 1, NULL, DOMID_SELF);
>  
>  	xen_mc_issue(PARAVIRT_LAZY_MMU);
> +	put_online_cpus_atomic();
>  }
>  
>  static unsigned long xen_read_cr3(void)
> diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
> index 4f7d259..7d753ae 100644
> --- a/arch/x86/xen/smp.c
> +++ b/arch/x86/xen/smp.c
> @@ -16,6 +16,7 @@
>  #include <linux/err.h>
>  #include <linux/slab.h>
>  #include <linux/smp.h>
> +#include <linux/cpu.h>
>  #include <linux/irq_work.h>
>  
>  #include <asm/paravirt.h>
> @@ -487,8 +488,10 @@ static void __xen_send_IPI_mask(const struct cpumask *mask,
>  {
>  	unsigned cpu;
>  
> +	get_online_cpus_atomic();
>  	for_each_cpu_and(cpu, mask, cpu_online_mask)
>  		xen_send_IPI_one(cpu, vector);
> +	put_online_cpus_atomic();
>  }
>  
>  static void xen_smp_send_call_function_ipi(const struct cpumask *mask)
> @@ -551,8 +554,10 @@ void xen_send_IPI_all(int vector)
>  {
>  	int xen_vector = xen_map_vector(vector);
>  
> +	get_online_cpus_atomic();
>  	if (xen_vector >= 0)
>  		__xen_send_IPI_mask(cpu_online_mask, xen_vector);
> +	put_online_cpus_atomic();
>  }
>  
>  void xen_send_IPI_self(int vector)
> @@ -572,20 +577,24 @@ void xen_send_IPI_mask_allbutself(const struct cpumask *mask,
>  	if (!(num_online_cpus() > 1))
>  		return;
>  
> +	get_online_cpus_atomic();
>  	for_each_cpu_and(cpu, mask, cpu_online_mask) {
>  		if (this_cpu == cpu)
>  			continue;
>  
>  		xen_smp_send_call_function_single_ipi(cpu);
>  	}
> +	put_online_cpus_atomic();
>  }
>  
>  void xen_send_IPI_allbutself(int vector)
>  {
>  	int xen_vector = xen_map_vector(vector);
>  
> +	get_online_cpus_atomic();
>  	if (xen_vector >= 0)
>  		xen_send_IPI_mask_allbutself(cpu_online_mask, xen_vector);
> +	put_online_cpus_atomic();
>  }
>  
>  static irqreturn_t xen_call_function_interrupt(int irq, void *dev_id)
> 
> --
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>
Srivatsa S. Bhat - Feb. 19, 2013, 6:29 p.m.
On 02/19/2013 11:40 PM, Konrad Rzeszutek Wilk wrote:
> On Tue, Jan 22, 2013 at 01:10:51PM +0530, Srivatsa S. Bhat wrote:
>> Once stop_machine() is gone from the CPU offline path, we won't be able to
>> depend on preempt_disable() or local_irq_disable() to prevent CPUs from
>> going offline from under us.
>>
>> Use the get/put_online_cpus_atomic() APIs to prevent CPUs from going offline,
>> while invoking from atomic context.
>>
>> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> 
> Weird. I see this in the patch but I don't see it in the header?

Meaning, you didn't get this email at all?

> Did you
> explicitly suppress the CC part?
> 

No.. I sent the entire patchset to a set of email ids and in addition to
that I CC'ed individual patches to the respective maintainers/lists (the
CC: list in the changelog). I used the --auto knob from stgit to do that.

> 
> Anyhow, the patch looks sane enough, thought I need to to run it through
> a test framework just to be on a sure side.
>

Sure, thank you. But you might want to test the v6 that I sent out
yesterday instead of v5. Oh, wait a min, you didn't get the v6 mail also?

Here it is, for your reference:
http://marc.info/?l=linux-kernel&m=136119260122255&w=2

Regards,
Srivatsa S. Bhat

>> Cc: Jeremy Fitzhardinge <jeremy@goop.org>
>> Cc: "H. Peter Anvin" <hpa@zytor.com>
>> Cc: x86@kernel.org
>> Cc: xen-devel@lists.xensource.com
>> Cc: virtualization@lists.linux-foundation.org
>> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
>> ---

Patch

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 01de35c..6a95a15 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -39,6 +39,7 @@ 
  * Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007
  */
 #include <linux/sched.h>
+#include <linux/cpu.h>
 #include <linux/highmem.h>
 #include <linux/debugfs.h>
 #include <linux/bug.h>
@@ -1163,9 +1164,13 @@  static void xen_drop_mm_ref(struct mm_struct *mm)
  */
 static void xen_exit_mmap(struct mm_struct *mm)
 {
-	get_cpu();		/* make sure we don't move around */
+	/*
+	 * Make sure we don't move around, and prevent CPUs from going
+	 * offline.
+	 */
+	get_online_cpus_atomic();
 	xen_drop_mm_ref(mm);
-	put_cpu();
+	put_online_cpus_atomic();
 
 	spin_lock(&mm->page_table_lock);
 
@@ -1371,6 +1376,7 @@  static void xen_flush_tlb_others(const struct cpumask *cpus,
 	args->op.arg2.vcpumask = to_cpumask(args->mask);
 
 	/* Remove us, and any offline CPUS. */
+	get_online_cpus_atomic();
 	cpumask_and(to_cpumask(args->mask), cpus, cpu_online_mask);
 	cpumask_clear_cpu(smp_processor_id(), to_cpumask(args->mask));
 
@@ -1383,6 +1389,7 @@  static void xen_flush_tlb_others(const struct cpumask *cpus,
 	MULTI_mmuext_op(mcs.mc, &args->op, 1, NULL, DOMID_SELF);
 
 	xen_mc_issue(PARAVIRT_LAZY_MMU);
+	put_online_cpus_atomic();
 }
 
 static unsigned long xen_read_cr3(void)
diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index 4f7d259..7d753ae 100644
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -16,6 +16,7 @@ 
 #include <linux/err.h>
 #include <linux/slab.h>
 #include <linux/smp.h>
+#include <linux/cpu.h>
 #include <linux/irq_work.h>
 
 #include <asm/paravirt.h>
@@ -487,8 +488,10 @@  static void __xen_send_IPI_mask(const struct cpumask *mask,
 {
 	unsigned cpu;
 
+	get_online_cpus_atomic();
 	for_each_cpu_and(cpu, mask, cpu_online_mask)
 		xen_send_IPI_one(cpu, vector);
+	put_online_cpus_atomic();
 }
 
 static void xen_smp_send_call_function_ipi(const struct cpumask *mask)
@@ -551,8 +554,10 @@  void xen_send_IPI_all(int vector)
 {
 	int xen_vector = xen_map_vector(vector);
 
+	get_online_cpus_atomic();
 	if (xen_vector >= 0)
 		__xen_send_IPI_mask(cpu_online_mask, xen_vector);
+	put_online_cpus_atomic();
 }
 
 void xen_send_IPI_self(int vector)
@@ -572,20 +577,24 @@  void xen_send_IPI_mask_allbutself(const struct cpumask *mask,
 	if (!(num_online_cpus() > 1))
 		return;
 
+	get_online_cpus_atomic();
 	for_each_cpu_and(cpu, mask, cpu_online_mask) {
 		if (this_cpu == cpu)
 			continue;
 
 		xen_smp_send_call_function_single_ipi(cpu);
 	}
+	put_online_cpus_atomic();
 }
 
 void xen_send_IPI_allbutself(int vector)
 {
 	int xen_vector = xen_map_vector(vector);
 
+	get_online_cpus_atomic();
 	if (xen_vector >= 0)
 		xen_send_IPI_mask_allbutself(cpu_online_mask, xen_vector);
+	put_online_cpus_atomic();
 }
 
 static irqreturn_t xen_call_function_interrupt(int irq, void *dev_id)