[PATCH v6 36/46] m32r: Use get/put_online_cpus_atomic() to preventCPU offline

[Srivatsa S. Bhat]

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: Hirokazu Takata <takata@xxxxxxxxxxxxxx>
Cc: linux-m32r@xxxxxxxxxxxxxxxxx
Cc: linux-m32r-ja@xxxxxxxxxxxxxxxxx
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@xxxxxxxxxxxxxxxxxx>
---

 arch/m32r/kernel/smp.c |   12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/arch/m32r/kernel/smp.c b/arch/m32r/kernel/smp.c
index ce7aea3..0dad4d7 100644
--- a/arch/m32r/kernel/smp.c
+++ b/arch/m32r/kernel/smp.c
@@ -151,7 +151,7 @@ void smp_flush_cache_all(void)
 	cpumask_t cpumask;
 	unsigned long *mask;
 
-	preempt_disable();
+	get_online_cpus_atomic();
 	cpumask_copy(&cpumask, cpu_online_mask);
 	cpumask_clear_cpu(smp_processor_id(), &cpumask);
 	spin_lock(&flushcache_lock);
@@ -162,7 +162,7 @@ void smp_flush_cache_all(void)
 	while (flushcache_cpumask)
 		mb();
 	spin_unlock(&flushcache_lock);
-	preempt_enable();
+	put_online_cpus_atomic();
 }
 
 void smp_flush_cache_all_interrupt(void)
@@ -250,7 +250,7 @@ void smp_flush_tlb_mm(struct mm_struct *mm)
 	unsigned long *mmc;
 	unsigned long flags;
 
-	preempt_disable();
+	get_online_cpus_atomic();
 	cpu_id = smp_processor_id();
 	mmc = &mm->context[cpu_id];
 	cpumask_copy(&cpu_mask, mm_cpumask(mm));
@@ -268,7 +268,7 @@ void smp_flush_tlb_mm(struct mm_struct *mm)
 	if (!cpumask_empty(&cpu_mask))
 		flush_tlb_others(cpu_mask, mm, NULL, FLUSH_ALL);
 
-	preempt_enable();
+	put_online_cpus_atomic();
 }
 
 /*==========================================================================*
@@ -715,10 +715,12 @@ static void send_IPI_allbutself(int ipi_num, int try)
 {
 	cpumask_t cpumask;
 
+	get_online_cpus_atomic();
 	cpumask_copy(&cpumask, cpu_online_mask);
 	cpumask_clear_cpu(smp_processor_id(), &cpumask);
 
 	send_IPI_mask(&cpumask, ipi_num, try);
+	put_online_cpus_atomic();
 }
 
 /*==========================================================================*
@@ -750,6 +752,7 @@ static void send_IPI_mask(const struct cpumask *cpumask, int ipi_num, int try)
 	if (num_cpus <= 1)	/* NO MP */
 		return;
 
+	get_online_cpus_atomic();
 	cpumask_and(&tmp, cpumask, cpu_online_mask);
 	BUG_ON(!cpumask_equal(cpumask, &tmp));
 
@@ -760,6 +763,7 @@ static void send_IPI_mask(const struct cpumask *cpumask, int ipi_num, int try)
 	}
 
 	send_IPI_mask_phys(&physid_mask, ipi_num, try);
+	put_online_cpus_atomic();
 }
 
 /*==========================================================================*

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