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Subject[PATCH v6 37/46] MIPS: Use get/put_online_cpus_atomic() to prevent CPU offline
Date
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 fom
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: Ralf Baechle <ralf@linux-mips.org>
Cc: David Daney <david.daney@cavium.com>
Cc: linux-mips@linux-mips.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---

arch/mips/kernel/cevt-smtc.c | 8 ++++++++
arch/mips/kernel/smp.c | 16 ++++++++--------
arch/mips/kernel/smtc.c | 3 +++
arch/mips/mm/c-octeon.c | 4 ++--
4 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/arch/mips/kernel/cevt-smtc.c b/arch/mips/kernel/cevt-smtc.c
index 2e72d30..6fb311b 100644
--- a/arch/mips/kernel/cevt-smtc.c
+++ b/arch/mips/kernel/cevt-smtc.c
@@ -11,6 +11,7 @@
#include <linux/interrupt.h>
#include <linux/percpu.h>
#include <linux/smp.h>
+#include <linux/cpu.h>
#include <linux/irq.h>

#include <asm/smtc_ipi.h>
@@ -84,6 +85,8 @@ static int mips_next_event(unsigned long delta,
unsigned long nextcomp = 0L;
int vpe = current_cpu_data.vpe_id;
int cpu = smp_processor_id();
+
+ get_online_cpus_atomic();
local_irq_save(flags);
mtflags = dmt();

@@ -164,6 +167,7 @@ static int mips_next_event(unsigned long delta,
}
emt(mtflags);
local_irq_restore(flags);
+ put_online_cpus_atomic();
return 0;
}

@@ -180,6 +184,7 @@ void smtc_distribute_timer(int vpe)

repeat:
nextstamp = 0L;
+ get_online_cpus_atomic();
for_each_online_cpu(cpu) {
/*
* Find virtual CPUs within the current VPE who have
@@ -221,6 +226,9 @@ repeat:

}
}
+
+ put_online_cpus_atomic()
+
/* Reprogram for interrupt at next soonest timestamp for VPE */
if (ISVALID(nextstamp)) {
write_c0_compare(nextstamp);
diff --git a/arch/mips/kernel/smp.c b/arch/mips/kernel/smp.c
index 66bf4e2..3828afa 100644
--- a/arch/mips/kernel/smp.c
+++ b/arch/mips/kernel/smp.c
@@ -248,12 +248,12 @@ static inline void smp_on_other_tlbs(void (*func) (void *info), void *info)

static inline void smp_on_each_tlb(void (*func) (void *info), void *info)
{
- preempt_disable();
+ get_online_cpus_atomic();

smp_on_other_tlbs(func, info);
func(info);

- preempt_enable();
+ put_online_cpus_atomic();
}

/*
@@ -271,7 +271,7 @@ static inline void smp_on_each_tlb(void (*func) (void *info), void *info)

void flush_tlb_mm(struct mm_struct *mm)
{
- preempt_disable();
+ get_online_cpus_atomic();

if ((atomic_read(&mm->mm_users) != 1) || (current->mm != mm)) {
smp_on_other_tlbs(flush_tlb_mm_ipi, mm);
@@ -285,7 +285,7 @@ void flush_tlb_mm(struct mm_struct *mm)
}
local_flush_tlb_mm(mm);

- preempt_enable();
+ put_online_cpus_atomic();
}

struct flush_tlb_data {
@@ -305,7 +305,7 @@ void flush_tlb_range(struct vm_area_struct *vma, unsigned long start, unsigned l
{
struct mm_struct *mm = vma->vm_mm;

- preempt_disable();
+ get_online_cpus_atomic();
if ((atomic_read(&mm->mm_users) != 1) || (current->mm != mm)) {
struct flush_tlb_data fd = {
.vma = vma,
@@ -323,7 +323,7 @@ void flush_tlb_range(struct vm_area_struct *vma, unsigned long start, unsigned l
}
}
local_flush_tlb_range(vma, start, end);
- preempt_enable();
+ put_online_cpus_atomic();
}

static void flush_tlb_kernel_range_ipi(void *info)
@@ -352,7 +352,7 @@ static void flush_tlb_page_ipi(void *info)

void flush_tlb_page(struct vm_area_struct *vma, unsigned long page)
{
- preempt_disable();
+ get_online_cpus_atomic();
if ((atomic_read(&vma->vm_mm->mm_users) != 1) || (current->mm != vma->vm_mm)) {
struct flush_tlb_data fd = {
.vma = vma,
@@ -369,7 +369,7 @@ void flush_tlb_page(struct vm_area_struct *vma, unsigned long page)
}
}
local_flush_tlb_page(vma, page);
- preempt_enable();
+ put_online_cpus_atomic();
}

static void flush_tlb_one_ipi(void *info)
diff --git a/arch/mips/kernel/smtc.c b/arch/mips/kernel/smtc.c
index 1d47843..caf081e 100644
--- a/arch/mips/kernel/smtc.c
+++ b/arch/mips/kernel/smtc.c
@@ -22,6 +22,7 @@
#include <linux/sched.h>
#include <linux/smp.h>
#include <linux/cpumask.h>
+#include <linux/cpu.h>
#include <linux/interrupt.h>
#include <linux/kernel_stat.h>
#include <linux/module.h>
@@ -1143,6 +1144,7 @@ static irqreturn_t ipi_interrupt(int irq, void *dev_idm)
* for the current TC, so we ought not to have to do it explicitly here.
*/

+ get_online_cpus_atomic();
for_each_online_cpu(cpu) {
if (cpu_data[cpu].vpe_id != my_vpe)
continue;
@@ -1179,6 +1181,7 @@ static irqreturn_t ipi_interrupt(int irq, void *dev_idm)
}
}
}
+ put_online_cpus_atomic();

return IRQ_HANDLED;
}
diff --git a/arch/mips/mm/c-octeon.c b/arch/mips/mm/c-octeon.c
index 6ec04da..cd2c1ce 100644
--- a/arch/mips/mm/c-octeon.c
+++ b/arch/mips/mm/c-octeon.c
@@ -73,7 +73,7 @@ static void octeon_flush_icache_all_cores(struct vm_area_struct *vma)
mb();
octeon_local_flush_icache();
#ifdef CONFIG_SMP
- preempt_disable();
+ get_online_cpus_atomic();
cpu = smp_processor_id();

/*
@@ -88,7 +88,7 @@ static void octeon_flush_icache_all_cores(struct vm_area_struct *vma)
for_each_cpu(cpu, &mask)
octeon_send_ipi_single(cpu, SMP_ICACHE_FLUSH);

- preempt_enable();
+ put_online_cpus_atomic();
#endif
}



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