Re: [PATCH 0/5] x86-32: improve atomic64_t functions (v2)

From: H. Peter Anvin
Date: Mon Mar 01 2010 - 02:36:05 EST

On 02/26/2010 03:23 AM, Luca Barbieri wrote:
> Sent patches, both to conditionally perform the test and implement the
> functions for x86 and x86-64.

Yes, and with the test turned on, the kernel crashes immediately on boot
on x86-64.

Some minor investigation reveals the following:

lib/atomic64.c has the wrong return value for atomic64_add_unless().
With "wrong" I mean it is the opposite sense compared to
atomic_add_unless(), not just on x86 but on all architectures.

Accordingly, I have to conclude that lib/atomic64.c is buggy, and that
since your test matches that bug, I will have to conclude that your
x86-32 implementation is also buggy. Thus, please send patches to fix
your test and your 32-bit implementations (and preferrably
lib/atomic64.c too, but I can do that just fine.)

Cc: Paul Mackerras who did the generic atomic64_t implementation for
verification that this is indeed a bug.


H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at