From: "George Spelvin" <linux@sciencehorizons.net>
To: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
maddy@linux.vnet.ibm.com
Cc: acme@kernel.org, adrian.hunter@intel.com, bp@suse.de,
dsahern@gmail.com, jolsa@redhat.com, linux@horizon.com,
linux@rasmusvillemoes.dk, mpe@ellerman.id.au,
namhyung@kernel.org, wangnan0@huawei.com, yury.norov@gmail.com
Subject: Re: [PATCH] tools/perf: fix the word selected in find_*_bit
Date: 15 Jun 2016 08:44:09 -0400 [thread overview]
Message-ID: <20160615124409.6985.qmail@ns.sciencehorizons.net> (raw)
In-Reply-To: <1465990973-31483-1-git-send-email-maddy@linux.vnet.ibm.com>
Madhavan Srinivasan wrote:
> +#if (__BYTE_ORDER == __BIG_ENDIAN) && (BITS_PER_LONG != 64)
> + tmp = addr[(((nbits - 1)/BITS_PER_LONG) - (start / BITS_PER_LONG))]
> + ^ invert;
> +#else
> tmp = addr[start / BITS_PER_LONG] ^ invert;
> +#endif
Than you for diagnosing this problem, but I don't think the fix
is correct.
1) It's not clear that all users of _find_next_bit and for_each_set_bit()
want this change.
2) Is your code even correct? I'd think you'd want addr[x ^ 1]. Are you
sure you shpuld be reversing the whole array, and not just the halves of
each 64-bit word?
3) You've now broken the case of 32-bit big-endian kernel.
I think the proper solution is uglier than this. :-(
next prev parent reply other threads:[~2016-06-15 12:44 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-15 11:42 Madhavan Srinivasan
2016-06-15 12:44 ` George Spelvin [this message]
2016-06-16 7:21 ` Madhavan Srinivasan
2016-06-15 19:51 ` Yury Norov
2016-06-15 21:11 ` Yury Norov
2016-06-15 21:29 ` Arnaldo Carvalho de Melo
2016-06-16 1:27 ` [PATCH] tools include: Fix wrong macro definitions for cpu_to_le* for big endian He Kuang
2016-06-16 1:32 ` He Kuang
2016-06-16 1:32 ` [PATCH 1/2] tools include: Sync byteorder/generic.h He Kuang
2016-06-16 6:39 ` Jiri Olsa
2016-06-16 1:32 ` [PATCH 2/2] tools include: Fix wrong macro definitions for cpu_to_le* for big endian He Kuang
2016-06-16 6:21 ` kbuild test robot
2016-06-16 6:39 ` Jiri Olsa
2016-06-16 1:35 ` [PATCH] tools/perf: fix the word selected in find_*_bit Hekuang
2016-06-16 13:11 ` Madhavan Srinivasan
2016-06-16 7:15 ` Madhavan Srinivasan
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