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From: Henrik Rydberg on 20 Jun 2010 16:20
....

diff --git a/include/linux/buflock.h b/include/linux/buflock.h
index 3d5df22..05996d5 100644
--- a/include/linux/buflock.h
+++ b/include/linux/buflock.h
@@ -125,8 +125,8 @@ static inline unsigned int bufwrite_at(const struct buflock_
writer *bw)
*/
static inline void bufwrite_unlock(struct buflock_writer *bw)
{
- ++bw->head;
smp_wmb();
+ ++bw->head;
}

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From: Henrik Rydberg on 22 Jun 2010 10:00
Andrew Morton wrote:
[...]
> I don't understand why this has "lock" in its name.
>
> The API itself is a mixture of "bufwrite_foo" and "bufread_foo".
>
> It's all a bit chaotic. I'd suggest picking a sane name for the whole
> subsytem - perhaps "mrbuf" for "multi reader buffer"? Then
> consistently name all interface functions as "mrbuf_foo".
> mrbuf.h, mrbuf_write_lock(), etc.

Point taken.

>> +static __always_inline bool __must_check bufread_retry(struct buflock_reader *br, const struct buflock_writer *bw)
>> +{
>> + smp_rmb();
>> + if (unlikely(((br->tail - br->last) & bw->page) < bw->next - br->last))
>> + return true;
>> + ++br->tail;
>> + if (unlikely(br->head - br->tail > bw->page))
>> + br->tail = br->head;
>> + return false;
>> +}
>
> This looks too large to be inlined.
>
> What's the __always_inline for? Was gcc uninlining this within
> separate compilation units?

As you say, the function is large, and I am uncertain about the rules regarding
compiler reordering across general function calls. Starting a general function
with a memory barrier feels weird. Perhaps the function should be split?

Thanks,
Henrik

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