On Thu, 27 Jan 2011 09:24:34 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote: >
>
> I'll review. Against the roll-over, I think we just need to take lock.
> So, res_counter_read_u64() implementation was wrong. It should take lock.
> Please give me time.
>
As far as I can see usages of return value of res_counter_read_u64()
in memcontrol.c, all values are handle in u64 and no >> PAGE_SHIFT
to 'int' is not done. I'll see usage of u64 return value to
functions in other files from memcontrol.c
But, at least, this patch is required, I think. There are races.
==
res_counter_read_u64 reads u64 value without lock. It's dangerous
in 32bit environment. This patch adds lock.
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
---
include/linux/res_counter.h | 13 ++++++++++++-
kernel/res_counter.c | 2 +-
2 files changed, 13 insertions(+), 2 deletions(-)
Index: mmotm-0125/include/linux/res_counter.h
===================================================================
--- mmotm-0125.orig/include/linux/res_counter.h
+++ mmotm-0125/include/linux/res_counter.h
@@ -68,7 +68,18 @@ struct res_counter {
* @pos: and the offset.
*/
-u64 res_counter_read_u64(struct res_counter *counter, int member);
+u64 res_counter_read_u64_locked(struct res_counter *counter, int member);
+
+static inline u64 res_counter_read_u64(struct res_counter *counter, int member)
+{
+ unsigned long flags;
+ u64 ret;
+
+ spin_lock_irqsave(&counter->lock, flags);
+ ret = res_counter_read_u64_locked(counter, member);
+ spin_unlock_irqrestore(&counter->lock, flags);
+ return ret;
+}
ssize_t res_counter_read(struct res_counter *counter, int member,
const char __user *buf, size_t nbytes, loff_t *pos,
Index: mmotm-0125/kernel/res_counter.c
===================================================================
--- mmotm-0125.orig/kernel/res_counter.c
+++ mmotm-0125/kernel/res_counter.c
@@ -126,7 +126,7 @@ ssize_t res_counter_read(struct res_coun
pos, buf, s - buf);
}
-u64 res_counter_read_u64(struct res_counter *counter, int member)
+u64 res_counter_read_u64_locked(struct res_counter *counter, int member)
{
return *res_counter_member(counter, member);
}
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