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Date: Thu, 14 Jun 2012 18:36:42 +0900 From: Akinobu Mita <akinobu.mita@...il.com> To: Takuya Yoshikawa <takuya.yoshikawa@...il.com> Cc: Grant Grundler <grantgrundler@...il.com>, Takuya Yoshikawa <yoshikawa.takuya@....ntt.co.jp>, akpm@...ux-foundation.org, bhutchings@...arflare.com, grundler@...isc-linux.org, arnd@...db.de, benh@...nel.crashing.org, avi@...hat.com, mtosatti@...hat.com, linux-net-drivers@...arflare.com, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org, kvm@...r.kernel.org Subject: Re: [PATCH 2/5] drivers/net/ethernet/dec/tulip: Use standard __set_bit_le() function 2012/6/14 Takuya Yoshikawa <takuya.yoshikawa@...il.com>: > On Wed, 13 Jun 2012 08:21:18 -0700 > Grant Grundler <grantgrundler@...il.com> wrote: > >> >> >> Should this hash_table be converted from u16 hash_table[32] to >> >> >> DECLARE_BITMAP(hash_table, 16 * 32) to ensure that it is aligned >> >> >> on long-word boundary? >> >> > >> >> > I think hash_table is already long-word aligned because it is placed >> >> > right after a pointer. >> >> >> >> I recommend converting to proper bitmap. Because such an implicit >> >> assumption is easily broken by someone touching this function. >> > >> > Do you mean something like: >> > DECLARE_BITMAP(__hash_table, 16 * 32); >> > u16 *hash_table = (u16 *)__hash_table; >> > ? >> > >> > Grant, what do you think about this? >> >> Hi Takuya, >> two thoughts: >> 1) while I agree with Akinobu and thank him for pointing out a >> _potential_ alignment problem, this is a separate issue and your >> existing patch should go in anyway. There are probably other drivers >> with _potential_ alignment issues. Akinobu could get credit for >> finding them by submitting patches after reviewing calls to set_bit >> and set_bit_le() - similar to what you are doing now. > > I prefer approach 1. > > hash_table is local in build_setup_frame_hash(), so if further > improvement is also required, we can do that locally there later. This potential alignment problem is introduced by this patch. Because the original set_bit_le() in tulip driver can handle unaligned bitmap. This is why I recommended it should be fixed in this patch. But please just ignore me if I'm too much paranoid. And I'll handle this issue if no one wants to do it. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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