[PATCH 3.18 075/124] percpu: acquire pcpu_lock when updating pcpu_nr_empty_pop_pages

[Greg Kroah-Hartman]

3.18-stable review patch.  If anyone has any objections, please let me know.

--

From: Tahsin Erdogan 

commit 320661b08dd6f1746d5c7ab4eb435ec64b97cd45 upstream.

Update to pcpu_nr_empty_pop_pages in pcpu_alloc() is currently done
without holding pcpu_lock. This can lead to bad updates to the variable.
Add missing lock calls.

Fixes: b539b87fed37 ("percpu: implmeent pcpu_nr_empty_pop_pages and 
chunk->nr_populated")
Signed-off-by: Tahsin Erdogan 
Signed-off-by: Tejun Heo 
Signed-off-by: Greg Kroah-Hartman 

---
 mm/percpu.c |5 -
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -1012,8 +1012,11 @@ area_found:
mutex_unlock(_alloc_mutex);
}
 
-   if (chunk != pcpu_reserved_chunk)
+   if (chunk != pcpu_reserved_chunk) {
+   spin_lock_irqsave(_lock, flags);
pcpu_nr_empty_pop_pages -= occ_pages;
+   spin_unlock_irqrestore(_lock, flags);
+   }
 
if (pcpu_nr_empty_pop_pages < PCPU_EMPTY_POP_PAGES_LOW)
pcpu_schedule_balance_work();

[PATCH 3.18 075/124] percpu: acquire pcpu_lock when updating pcpu_nr_empty_pop_pages

[Greg Kroah-Hartman]

3.18-stable review patch.  If anyone has any objections, please let me know.

--

From: Tahsin Erdogan 

commit 320661b08dd6f1746d5c7ab4eb435ec64b97cd45 upstream.

Update to pcpu_nr_empty_pop_pages in pcpu_alloc() is currently done
without holding pcpu_lock. This can lead to bad updates to the variable.
Add missing lock calls.

Fixes: b539b87fed37 ("percpu: implmeent pcpu_nr_empty_pop_pages and 
chunk->nr_populated")
Signed-off-by: Tahsin Erdogan 
Signed-off-by: Tejun Heo 
Signed-off-by: Greg Kroah-Hartman 

---
 mm/percpu.c |5 -
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -1012,8 +1012,11 @@ area_found:
mutex_unlock(_alloc_mutex);
}
 
-   if (chunk != pcpu_reserved_chunk)
+   if (chunk != pcpu_reserved_chunk) {
+   spin_lock_irqsave(_lock, flags);
pcpu_nr_empty_pop_pages -= occ_pages;
+   spin_unlock_irqrestore(_lock, flags);
+   }
 
if (pcpu_nr_empty_pop_pages < PCPU_EMPTY_POP_PAGES_LOW)
pcpu_schedule_balance_work();