Messages in this thread Patch in this message | | | Date | Thu, 30 Dec 2010 00:26:34 -0500 | From | Jeff Mahoney <> | Subject | Re: [PATCH] taskstats: Use better ifdef for alignment |
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On 12/29/2010 07:14 PM, Andrew Morton wrote: > On Wed, 29 Dec 2010 19:12:08 -0500 Jeff Mahoney <jeffm@suse.com> wrote: > >> Commit 4be2c95d added a null field to align the taskstats structure but >> the discussion centered around ia64. The issue exists on other platforms >> with inefficient unaligned access and adding them piecemeal would be >> an unmaintainable mess. >> >> This patch uses Dave Miller's suggestion of using a combination of >> CONFIG_64BIT && !CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS to determine >> whether alignment is needed. >> >> Note that this will cause breakage on those platforms with applications >> like iotop which had hard-coded offsets into the packet to access the >> taskstats structure. > > That seems a very good reason to not apply the patch. > > Tell us more, please...
I don't want to rehash the same discussion, but any argument that applied to ia64 applies any other 64-bit arch other than powerpc and x86_64.
- -Jeff
>> The message seen on systems without the alignment fixes looks like: >> kernel unaligned access to 0xe000023879dca9bc, ip=0xa000000100133d10 >> >> The addresses may vary but resolve to locations inside __delayacct_add_tsk. >> >> Reported-by: David S. Miller <davem@davemloft.net> >> Signed-off-by: Jeff Mahoney <jeffm@suse.com> >> --- >> kernel/taskstats.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> --- a/kernel/taskstats.c >> +++ b/kernel/taskstats.c >> @@ -349,7 +349,7 @@ static int parse(struct nlattr *na, stru >> return ret; >> } >> >> -#ifdef CONFIG_IA64 >> +#if defined(CONFIG_64BIT) && !defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) >> #define TASKSTATS_NEEDS_PADDING 1 >> #endif >>
- -- Jeff Mahoney SUSE Labs -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.16 (GNU/Linux) Comment: Using GnuPG with SUSE - http://enigmail.mozdev.org/
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