linux-kernel - Re: [PATCH next v4 0/5] minmax: Relax type checks in min() and max().

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Date: Fri, 19 Jan 2024 09:23:55 +0100
From: Hans Verkuil <hverkuil@...all.nl>
To: Jiri Slaby <jirislaby@...nel.org>,
 Linus Torvalds <torvalds@...ux-foundation.org>
Cc: David Laight <David.Laight@...lab.com>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 "Matthew Wilcox (Oracle)" <willy@...radead.org>,
 Christoph Hellwig <hch@...radead.org>, "Jason A. Donenfeld"
 <Jason@...c4.com>, linux-media <linux-media@...r.kernel.org>
Subject: Re: [PATCH next v4 0/5] minmax: Relax type checks in min() and max().

On 19/01/2024 08:14, Jiri Slaby wrote:
> On 08. 01. 24, 19:19, Linus Torvalds wrote:
>> On Mon, 8 Jan 2024 at 03:46, Jiri Slaby <jirislaby@...il.com> wrote:
>>>
>>>     CPP [M] drivers/media/pci/solo6x10/solo6x10-p2m.i
>>> real    0m45,002s
>>>
>>> $ git revert 867046cc7027703f60a46339ffde91a1970f2901
>>>     CPP [M] drivers/media/pci/solo6x10/solo6x10-p2m.i
>>> real    0m11,132s
>>>
>>> $ git revert 4ead534fba42fc4fd41163297528d2aa731cd121
>>>     CPP [M] drivers/media/pci/solo6x10/solo6x10-p2m.i
>>> real    0m3,711s
>>
>> Ouch. Yeah, that's unfortunate. There's a lot of nested nasty macro
>> expansion there, but that timing is excessive.
>>
>> Sparse actually complains about that file:
>>
>>    drivers/media/pci/solo6x10/solo6x10-p2m.c:309:13: error: too long
>> token expansion
>>    drivers/media/pci/solo6x10/solo6x10-p2m.c:310:17: error: too long
>> token expansion
>>
>> and while that is a sparse limitation, it's still interesting. Having
>> that file expand to 122M is not ok.
>>
>> In this case, I suspect the right thing to do is to simply not use
>> min()/max() in that header at all, but do something like
>>
>>    --- a/drivers/media/pci/solo6x10/solo6x10-offsets.h
>>    +++ b/drivers/media/pci/solo6x10/solo6x10-offsets.h
>>    @@ -56,2 +56,5 @@
>>
>>    +#define MIN(X, Y) ((X) < (Y) ? (X) : (Y))
>>    +#define MAX(X, Y) ((X) > (Y) ? (X) : (Y))
>>    +
>>     #define SOLO_MP4E_EXT_ADDR(__solo) \
>>    @@ -59,4 +62,4 @@
>>     #define SOLO_MP4E_EXT_SIZE(__solo) \
>>    -     max((..),                               \
>>    -         min(((..) - \
>>    +     MAX((..),                               \
>>    +         MIN(((..) - \
>>                   ..), 0x00ff0000))
>>    @@ -67,4 +70,4 @@
>>     #define SOLO_JPEG_EXT_SIZE(__solo) \
>>    -     max(..,                         \
>>    -         min(..)
>>    +     MAX(..,                         \
>>    +         MIN(..)
>>
>> and avoid this issue.
> 
> So can someone pick up 20240113183334.1690740-1-aurelien@...el32.net so that we are done with this? I see neither Hans, nor Linus got to take it yet.

I replied here:

https://lore.kernel.org/all/fd143cf8-5e3d-4d80-8b53-b05980558e45@xs4all.nl/

Either Linus can pick it up directly during the merge window, or it will
appear in a media fixes PR once rc1 is released.

Regards,

	Hans

> 
>> That said, I'm sure this thing exists to a smaller degree elsewhere. I
>> wonder if we could simplify our min/max type tests.
> I assume we don't care with solo fixed? Hans pointed out ath11k too. Even if there is size increase in the preproc file, I don't see much of compile time increase there.
> 
> thanks,