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([2600:1700:e321:62f0:da43:aeff:fecc:bfd5]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-21c2d4042f8sm35530375ad.236.2025.01.18.13.59.36 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 18 Jan 2025 13:59:38 -0800 (PST) Message-ID: <0f28a0b7-c24d-47d8-92f0-8957207ea309@roeck-us.net> Date: Sat, 18 Jan 2025 13:59:36 -0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: Buiild error in i915/xe To: Linus Torvalds Cc: David Laight , David Laight , Arnd Bergmann , "linux-kernel@vger.kernel.org" , Jens Axboe , Matthew Wilcox , Christoph Hellwig , Andrew Morton , Andy Shevchenko , Dan Carpenter , "Jason A . Donenfeld" , "pedro.falcato@gmail.com" , Mateusz Guzik , "linux-mm@kvack.org" , Lorenzo Stoakes , intel-xe@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, David Airlie , Simona Vetter , Jani Nikula , Rodrigo Vivi References: <34d53778977747f19cce2abb287bb3e6@AcuMS.aculab.com> <20250118170959.3aa56f4d@pumpkin> <29ef57a1-e4dd-4d5d-8726-f1f79c698b66@roeck-us.net> Content-Language: en-US From: Guenter Roeck Autocrypt: addr=linux@roeck-us.net; keydata= xsFNBE6H1WcBEACu6jIcw5kZ5dGeJ7E7B2uweQR/4FGxH10/H1O1+ApmcQ9i87XdZQiB9cpN RYHA7RCEK2dh6dDccykQk3bC90xXMPg+O3R+C/SkwcnUak1UZaeK/SwQbq/t0tkMzYDRxfJ7 nyFiKxUehbNF3r9qlJgPqONwX5vJy4/GvDHdddSCxV41P/ejsZ8PykxyJs98UWhF54tGRWFl 7i1xvaDB9lN5WTLRKSO7wICuLiSz5WZHXMkyF4d+/O5ll7yz/o/JxK5vO/sduYDIlFTvBZDh gzaEtNf5tQjsjG4io8E0Yq0ViobLkS2RTNZT8ICq/Jmvl0SpbHRvYwa2DhNsK0YjHFQBB0FX IdhdUEzNefcNcYvqigJpdICoP2e4yJSyflHFO4dr0OrdnGLe1Zi/8Xo/2+M1dSSEt196rXaC kwu2KgIgmkRBb3cp2vIBBIIowU8W3qC1+w+RdMUrZxKGWJ3juwcgveJlzMpMZNyM1jobSXZ0 VHGMNJ3MwXlrEFPXaYJgibcg6brM6wGfX/LBvc/haWw4yO24lT5eitm4UBdIy9pKkKmHHh7s jfZJkB5fWKVdoCv/omy6UyH6ykLOPFugl+hVL2Prf8xrXuZe1CMS7ID9Lc8FaL1ROIN/W8Vk BIsJMaWOhks//7d92Uf3EArDlDShwR2+D+AMon8NULuLBHiEUQARAQABzTJHdWVudGVyIFJv ZWNrIChMaW51eCBhY2NvdW50KSA8bGludXhAcm9lY2stdXMubmV0PsLBgQQTAQIAKwIbAwYL CQgHAwIGFQgCCQoLBBYCAwECHgECF4ACGQEFAlVcphcFCRmg06EACgkQyx8mb86fmYFg0RAA nzXJzuPkLJaOmSIzPAqqnutACchT/meCOgMEpS5oLf6xn5ySZkl23OxuhpMZTVX+49c9pvBx hpvl5bCWFu5qC1jC2eWRYU+aZZE4sxMaAGeWenQJsiG9lP8wkfCJP3ockNu0ZXXAXwIbY1O1 c+l11zQkZw89zNgWgKobKzrDMBFOYtAh0pAInZ9TSn7oA4Ctejouo5wUugmk8MrDtUVXmEA9 7f9fgKYSwl/H7dfKKsS1bDOpyJlqhEAH94BHJdK/b1tzwJCFAXFhMlmlbYEk8kWjcxQgDWMu GAthQzSuAyhqyZwFcOlMCNbAcTSQawSo3B9yM9mHJne5RrAbVz4TWLnEaX8gA5xK3uCNCeyI sqYuzA4OzcMwnnTASvzsGZoYHTFP3DQwf2nzxD6yBGCfwNGIYfS0i8YN8XcBgEcDFMWpOQhT Pu3HeztMnF3HXrc0t7e5rDW9zCh3k2PA6D2NV4fews9KDFhLlTfCVzf0PS1dRVVWM+4jVl6l HRIAgWp+2/f8dx5vPc4Ycp4IsZN0l1h9uT7qm1KTwz+sSl1zOqKD/BpfGNZfLRRxrXthvvY8 BltcuZ4+PGFTcRkMytUbMDFMF9Cjd2W9dXD35PEtvj8wnEyzIos8bbgtLrGTv/SYhmPpahJA l8hPhYvmAvpOmusUUyB30StsHIU2LLccUPPOwU0ETofVZwEQALlLbQeBDTDbwQYrj0gbx3bq 7kpKABxN2MqeuqGr02DpS9883d/t7ontxasXoEz2GTioevvRmllJlPQERVxM8gQoNg22twF7 pB/zsrIjxkE9heE4wYfN1AyzT+AxgYN6f8hVQ7Nrc9XgZZe+8IkuW/Nf64KzNJXnSH4u6nJM J2+Dt274YoFcXR1nG76Q259mKwzbCukKbd6piL+VsT/qBrLhZe9Ivbjq5WMdkQKnP7gYKCAi pNVJC4enWfivZsYupMd9qn7Uv/oCZDYoBTdMSBUblaLMwlcjnPpOYK5rfHvC4opxl+P/Vzyz 6WC2TLkPtKvYvXmdsI6rnEI4Uucg0Au/Ulg7aqqKhzGPIbVaL+U0Wk82nz6hz+WP2ggTrY1w ZlPlRt8WM9w6WfLf2j+PuGklj37m+KvaOEfLsF1v464dSpy1tQVHhhp8LFTxh/6RWkRIR2uF I4v3Xu/k5D0LhaZHpQ4C+xKsQxpTGuYh2tnRaRL14YMW1dlI3HfeB2gj7Yc8XdHh9vkpPyuT nY/ZsFbnvBtiw7GchKKri2gDhRb2QNNDyBnQn5mRFw7CyuFclAksOdV/sdpQnYlYcRQWOUGY HhQ5eqTRZjm9z+qQe/T0HQpmiPTqQcIaG/edgKVTUjITfA7AJMKLQHgp04Vylb+G6jocnQQX JqvvP09whbqrABEBAAHCwWUEGAECAA8CGwwFAlVcpi8FCRmg08MACgkQyx8mb86fmYHNRQ/+ J0OZsBYP4leJvQF8lx9zif+v4ZY/6C9tTcUv/KNAE5leyrD4IKbnV4PnbrVhjq861it/zRQW cFpWQszZyWRwNPWUUz7ejmm9lAwPbr8xWT4qMSA43VKQ7ZCeTQJ4TC8kjqtcbw41SjkjrcTG wF52zFO4bOWyovVAPncvV9eGA/vtnd3xEZXQiSt91kBSqK28yjxAqK/c3G6i7IX2rg6pzgqh hiH3/1qM2M/LSuqAv0Rwrt/k+pZXE+B4Ud42hwmMr0TfhNxG+X7YKvjKC+SjPjqp0CaztQ0H nsDLSLElVROxCd9m8CAUuHplgmR3seYCOrT4jriMFBtKNPtj2EE4DNV4s7k0Zy+6iRQ8G8ng QjsSqYJx8iAR8JRB7Gm2rQOMv8lSRdjva++GT0VLXtHULdlzg8VjDnFZ3lfz5PWEOeIMk7Rj trjv82EZtrhLuLjHRCaG50OOm0hwPSk1J64R8O3HjSLdertmw7eyAYOo4RuWJguYMg5DRnBk WkRwrSuCn7UG+qVWZeKEsFKFOkynOs3pVbcbq1pxbhk3TRWCGRU5JolI4ohy/7JV1TVbjiDI HP/aVnm6NC8of26P40Pg8EdAhajZnHHjA7FrJXsy3cyIGqvg9os4rNkUWmrCfLLsZDHD8FnU mDW4+i+XlNFUPUYMrIKi9joBhu18ssf5i5Q= In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: B8BFD160002 X-Stat-Signature: dh4ipo5gr7ckf5rxbtujbadjsduz99du X-Rspam-User: X-Rspamd-Server: rspam12 X-HE-Tag: 1737237580-839176 X-HE-Meta: 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 O5Ggq1I0 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 1/18/25 13:21, Linus Torvalds wrote: > On Sat, 18 Jan 2025 at 09:49, Guenter Roeck wrote: >> >> No idea why the compiler would know that the values are invalid. > > It's not that the compiler knows tat they are invalid, but I bet what > happens is in scale() (and possibly other places that do similar > checks), which does this: > > WARN_ON(source_min > source_max); > ... > source_val = clamp(source_val, source_min, source_max); > > and the compiler notices that the ordering comparison in the first > WARN_ON() is the same as the one in clamp(), so it basically converts > the logic to > > if (source_min > source_max) { > WARN(..); > /* Do the clamp() knowing that source_min > source_max */ > source_val = clamp(source_val, source_min, source_max); > } else { > /* Do the clamp knowing that source_min <= source_max */ > source_val = clamp(source_val, source_min, source_max); > } > > (obviously I dropped the other WARN_ON in the conversion, it wasn't > relevant for this case). > > And now that first clamp() case is done with source_min > source_max, > and it triggers that build error because that's invalid. > > So the condition is not statically true in the *source* code, but in > the "I have moved code around to combine tests" case it now *is* > statically true as far as the compiler is concerned. > Yes, turns out I can reproduce the problem by adding WARN_ON() ahead of similar clamp() calls (see below). However, I can only reproduce it with gcc 13.3 for parisc. I don't see the problem with other cross compilers (I tried arm, powerpc, and loongarch64). Compilers are weird :-(. I am not sure what to do here. That kind of problem seems difficult to avoid, and I am sure we will hit it again elsewhere. Should I declare gcc 13.x off limits for parisc builds ? Guenter --- diff --git a/drivers/input/mousedev.c b/drivers/input/mousedev.c index 505c562a5daa..71c0da31a9d2 100644 --- a/drivers/input/mousedev.c +++ b/drivers/input/mousedev.c @@ -179,6 +179,7 @@ static void mousedev_abs_event(struct input_dev *dev, struct mousedev *mousedev, if (size == 0) size = xres ? : 1; + WARN_ON(min > max); value = clamp(value, min, max); mousedev->packet.x = ((value - min) * xres) / size;