On 11/10/20 5:18 PM, Kees Cook wrote:
On Tue, Nov 10, 2020 at 09:43:02PM +0100, Greg KH wrote:
On Tue, Nov 10, 2020 at 09:41:40PM +0100, Greg KH wrote:
On Tue, Nov 10, 2020 at 12:53:27PM -0700, Shuah Khan wrote:
+Decrement interface
+-------------------
+
+Decrements sequence number and doesn't return the new value. ::
+
+ seqnum32_dec() --> atomic_dec()
+ seqnum64_dec() --> atomic64_dec()
Why would you need to decrement a sequence number? Shouldn't they just
always go up?
I see you use them in your patch 12/13, but I don't think that really is
a sequence number there, but rather just some other odd value :)
To that end, they should likely be internally cast to u32 and u64 (and
why is seqnum64 ifdef on CONFIG_64BIT?).
I had a reason for doing this, can't recall. I will revisit and remove
it which is ideal. I have to look at CONFIG_GENERIC_ATOMIC64 as well.
Not seeing any errors with my config which has CONFIG_64BIT=y
Note, other than this, I like the idea. It makes it obvious what these
atomic variables are being used for, and they can't be abused for other
things. Nice work.
Thanks.
Agreed: this is a clear wrapping sequence counter. It's only abuse would
be using it in a place where wrapping actually is _not_ safe. (bikeshed:
can we call it wrap_u32 and wrap_u64?)
Still like seqnum_ops.
There is seqcount_t in seqlock.h which is a totally different feature.
thanks,
-- Shuah
