[PATCH v2 31/45] alpha/smp: Use get/put_online_cpus_atomic() to prevent CPU offline

["Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>]

Once stop_machine() is gone from the CPU offline path, we won't be able
to depend on disabling preemption 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: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-alpha@vger.kernel.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---

 arch/alpha/kernel/smp.c |   19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/arch/alpha/kernel/smp.c b/arch/alpha/kernel/smp.c
index 7b60834..e147268 100644
--- a/arch/alpha/kernel/smp.c
+++ b/arch/alpha/kernel/smp.c
@@ -497,7 +497,6 @@ smp_cpus_done(unsigned int max_cpus)
 	       ((bogosum + 2500) / (5000/HZ)) % 100);
 }
 
-\f
 void
 smp_percpu_timer_interrupt(struct pt_regs *regs)
 {
@@ -681,7 +680,7 @@ ipi_flush_tlb_mm(void *x)
 void
 flush_tlb_mm(struct mm_struct *mm)
 {
-	preempt_disable();
+	get_online_cpus_atomic();
 
 	if (mm == current->active_mm) {
 		flush_tlb_current(mm);
@@ -693,7 +692,7 @@ flush_tlb_mm(struct mm_struct *mm)
 				if (mm->context[cpu])
 					mm->context[cpu] = 0;
 			}
-			preempt_enable();
+			put_online_cpus_atomic();
 			return;
 		}
 	}
@@ -702,7 +701,7 @@ flush_tlb_mm(struct mm_struct *mm)
 		printk(KERN_CRIT "flush_tlb_mm: timed out\n");
 	}
 
-	preempt_enable();
+	put_online_cpus_atomic();
 }
 EXPORT_SYMBOL(flush_tlb_mm);
 
@@ -730,7 +729,7 @@ flush_tlb_page(struct vm_area_struct *vma, unsigned long addr)
 	struct flush_tlb_page_struct data;
 	struct mm_struct *mm = vma->vm_mm;
 
-	preempt_disable();
+	get_online_cpus_atomic();
 
 	if (mm == current->active_mm) {
 		flush_tlb_current_page(mm, vma, addr);
@@ -742,7 +741,7 @@ flush_tlb_page(struct vm_area_struct *vma, unsigned long addr)
 				if (mm->context[cpu])
 					mm->context[cpu] = 0;
 			}
-			preempt_enable();
+			put_online_cpus_atomic();
 			return;
 		}
 	}
@@ -755,7 +754,7 @@ flush_tlb_page(struct vm_area_struct *vma, unsigned long addr)
 		printk(KERN_CRIT "flush_tlb_page: timed out\n");
 	}
 
-	preempt_enable();
+	put_online_cpus_atomic();
 }
 EXPORT_SYMBOL(flush_tlb_page);
 
@@ -786,7 +785,7 @@ flush_icache_user_range(struct vm_area_struct *vma, struct page *page,
 	if ((vma->vm_flags & VM_EXEC) == 0)
 		return;
 
-	preempt_disable();
+	get_online_cpus_atomic();
 
 	if (mm == current->active_mm) {
 		__load_new_mm_context(mm);
@@ -798,7 +797,7 @@ flush_icache_user_range(struct vm_area_struct *vma, struct page *page,
 				if (mm->context[cpu])
 					mm->context[cpu] = 0;
 			}
-			preempt_enable();
+			put_online_cpus_atomic();
 			return;
 		}
 	}
@@ -807,5 +806,5 @@ flush_icache_user_range(struct vm_area_struct *vma, struct page *page,
 		printk(KERN_CRIT "flush_icache_page: timed out\n");
 	}
 
-	preempt_enable();
+	put_online_cpus_atomic();
 }