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4 Apr 2025 01:47:06 +0200 Message-ID: <8b7dedfc-b97d-4ff8-86af-8c92b3fb37cf@o2.pl> Date: Fri, 4 Apr 2025 01:46:19 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [ BUG: Invalid wait context ] rtc_lock at: mc146818_avoid_UIP To: Thomas Gleixner , Borislav Petkov , linux-rtc@vger.kernel.org, Alexandre Belloni Cc: lkml , Frederic Weisbecker , Peter Zijlstra , Sebastian Andrzej Siewior , Chris Bainbridge References: <20250330113202.GAZ-krsjAnurOlTcp-@fat_crate.local> <87sempv17b.ffs@tglx> Content-Language: en-GB, pl From: =?UTF-8?Q?Mateusz_Jo=C5=84czyk?= Autocrypt: addr=mat.jonczyk@o2.pl; keydata= xsFNBFqMDyQBEAC2VYhOvwXdcGfmMs9amNUFjGFgLixeS2C1uYwaC3tYqjgDQNo/qDoPh52f ExoTMJRqx48qvvY/i6iwia7wOTBxbYCBDqGYxDudjtL41ko8AmbGOSkxJww5X/2ZAtFjUJxO QjNESFlRscMfDv5vcCvtH7PaJJob4TBZvKxdL4VCDCgEsmOadTy5hvwv0rjNjohau1y4XfxU DdvOcl6LpWMEezsHGc/PbSHNAKtVht4BZYg66kSEAhs2rOTN6pnWJVd7ErauehrET2xo2JbO 4lAv0nbXmCpPj37ZvURswCeP8PcHoA1QQKWsCnHU2WeVw+XcvR/hmFMI2QnE6V/ObHAb9bzg jxSYVZRAWVsdNakfT7xhkaeHjEQMVRQYBL6bqrJMFFXyh9YDj+MALjyb5hDG3mUcB4Wg7yln DRrda+1EVObfszfBWm2pC9Vz1QUQ4CD88FcmrlC7n2witke3gr38xmiYBzDqi1hRmrSj2WnS RP/s9t+C8M8SweQ2WuoVBLWUvcULYMzwy6mte0aSA8XV6+02a3VuBjP/6Y8yZUd0aZfAHyPi Rf60WVjYNRSeg27lZ9DJmHjSfZNn1FrtZi3W9Ff6bry/SY9D136qXBQxPYxXQfaGDhVeLUVF Q+NIZ6NEjqrLQ07LEvUW2Qzk2q851/IaXZPtP6swx0gqrpjNrwARAQABzSRNYXRldXN6IEpv xYRjenlrIDxtYXQuam9uY3p5a0BvMi5wbD7CwX4EEwECACgFAlqMDyQCGwMFCRLMAwAGCwkI BwMCBhUIAgkKCwQWAgMBAh4BAheAAAoJEPvWWrhhCv7Gb0MQAJVIpJ1KAOH6WaT8e65xZulI 1jkwGwNp+3bWWc5eLjKUnXtOYpa9oIsUUAqvh/L8MofGtM1V11kSX9dEloyqlqDyNSQk0h52 hZxMsCQyzjGOcBAi0zmWGYB4xu6SXj4LpVpIPW0sogduEOfbC0i7uAIyotHgepQ8RPGmZoXU 9bzFCyqZ8kAqwOoCCx+ccnXtbnlAXQmDb88cIprAU+Elk4k4t7Bpjn2ek4fv35PsvsBdRTq3 ADg8sGuq4KQXhbY53n1tyiab3M88uv6Cv//Ncgx+AqMdXq2AJ7amFsYdvkTC98sx20qk6Cul oHggmCre4MBcDD4S0qDXo5Z9NxVR/e9yUHxGLc5BlNj+FJPO7zwvkmIaMMnMlbydWVke0FSR AzJaEV/NNZKYctw2wYThdXPiz/y7aKd6/sM1jgPlleQhs3tZAIdjPfFjGdeeggv668M7GmKl +SEzpeFQ4b0x64XfLfLXX8GP/ArTuxEfJX4L05/Y9w9AJwXCVEwW4q17v8gNsPyVUVEdIroK cve6cgNNSWoxTaYcATePmkKnrAPqfg+6qFM4TuOWmyzCLQ1YoUZMxH+ddivDQtlKCp6JgGCz c9YCESxVii0vo8TsHdIAjQ/px9KsuYBmOlKnHXKbj6BsE/pkMMKQg/L415dvKzhLm2qVih7I U16IAtK5b7RpzsFNBFqMDyQBEACclVvbzpor4XfU6WLUofqnO3QSTwDuNyoNQaE4GJKEXA+p Bw5/D2ruHhj1Bgs6Qx7G4XL3odzO1xT3Iz6w26ZrxH69hYjeTdT8VW4EoYFvliUvgye2cC01 ltYrMYV1IBXwJqSEAImU0Xb+AItAnHA1NNUUb9wKHvOLrW4Y7Ntoy1tp7Vww2ecAWEIYjcO6 AMoUX8Q6gfVPxVEQv1EpspSwww+x/VlDGEiiYO4Ewm4MMSP4bmxsTmPb/f/K3rv830ZCQ5Ds U0rzUMG2CkyF45qXVWZ974NqZIeVCTE+liCTU7ARX1bN8VlU/yRs/nP2ISO0OAAMBKea7slr mu93to9gXNt3LEt+5aVIQdwEwPcqR09vGvTWdRaEQPqgkOJFyiZ0vYAUTwtITyjYxZWJbKJh JFaHpMds9kZLF9bH45SGb64uZrrE2eXTyI3DSeUS1YvMlJwKGumRTPXIzmVQ5PHiGXr2/9S4 16W9lBDJeHhmcVOsn+04x5KIxHtqAP3mkMjDBYa0A3ksqD84qUBNuEKkZKgibBbs4qT35oXf kgWJtW+JziZf6LYx4WvRa80VDIIYCcQM6TrpsXIJI+su5qpzON1XJQG2iswY8PJ40pkRI9Sm kfTFrHOgiTpwZnI9saWqJh2ABavtnKZ1CtAY2VA8gmEqQeqs2hjdiNHAmRxR2wARAQABwsFl BBgBAgAPBQJajA8kAhsMBQkSzAMAAAoJEPvWWrhhCv7GhpYP/1tH/Kc35OgWu2lsgJxR9Z49 4q+yYAuu11p0aQidL5utMFiemYHvxh/sJ4vMq65uPQXoQ3vo8lu9YR/p8kEt8jbljJusw6xQ iKA1Cc68xtseiKcUrjmN/rk3csbT+Qj2rZwkgod8v9GlKo6BJXMcKGbHb1GJtLF5HyI1q4j/ zfeu7G1gVjGTx8e2OLyuBJp0HlFXWs2vWSMesmZQIBVNyyL9mmDLEwO4ULK2quF6RYtbvg+2 PMyomNAaQB4s1UbXAO87s75hM79iszIzak2am4dEjTx+uYCWpvcw3rRDz7aMs401CphrlMKr WndS5qYcdiS9fvAfu/Jp5KIawpM0tVrojnKWCKHG4UnJIn+RF26+E7bjzE/Q5/NpkMblKD/Y 6LHzJWsnLnL1o7MUARU++ztOl2Upofyuj7BSath0N632+XCTXk9m5yeDCl/UzPbP9brIChuw gF7DbkdscM7fkYzkUVRJM45rKOupy5Z03EtAzuT5Z/If3qJPU0txAJsquDohppFsGHrzn/X2 0nI2LedLnIMUWwLRT4EvdYzsbP6im/7FXps15jaBOreobCaWTWtKtwD2LNI0l9LU9/RF+4Ac gwYu1CerMmdFbSo8ZdnaXlbEHinySUPqKmLHmPgDfxKNhfRDm1jJcGATkHCP80Fww8Ihl8aS TANkZ3QqXNX2 In-Reply-To: <87sempv17b.ffs@tglx> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-WP-MailID: d63111ab4b34202c8c63b3759b5597c4 X-WP-AV: skaner antywirusowy Poczty o2 X-WP-SPAM: NO 0000000 [4XMk] W dniu 3.04.2025 o 15:12, Thomas Gleixner pisze: > On Sun, Mar 30 2025 at 13:32, Borislav Petkov wrote: >> while playing with suspend to RAM, I got this lockdep splat below. >> >> Poking around I found: >> >> ec5895c0f2d8 ("rtc: mc146818-lib: extract mc146818_avoid_UIP") >> >> which is doing this funky taking and dropping the rtc_lock and I guess that's >> inherited from ye olde times. >> >> I "fixed" it so lockdeup doesn't warn by converting rtc_lock to a raw spinlock >> but this is definitely not the right fix so let me bounce it off to the folks >> on Cc who might have a better idea perhaps... > Converting it to a raw lock "fixes" the problem, but RT people will hunt > you down with a big latency bat. > > But this is not related to the commit above and not new. > > timekeeping_suspend() has always invoked mach_get_cmos_time() with the > freeze lock held and mc146818_get_time() has always locked rtc_lock. > > I wonder, why this splat hasn't popped before. On RT lockdep should have > complained forever. Sebastian??? Hello, I was able to trigger the bug on Linux 6.1.0 with CONFIG_PROVE_RAW_LOCK_NESTING enabled and I suspect it can be triggered much earlier. It is likely that only after commit 560af5dc839eef ("lockdep: Enable PROVE_RAW_LOCK_NESTING with PROVE_LOCKING.") people are seeing this simply because no one previously did the test with CONFIG_PROVE_RAW_LOCK_NESTING=y. See https://lore.kernel.org/all/CAP-bSRZ0CWyZZsMtx046YV8L28LhY0fson2g4EqcwRAVN1Jk+Q@mail.gmail.com/ : > This splat happens on suspend/resume on a HP laptop. It doesn't appear > to be a recent regression, as a bisect only leads to 560af5dc839e > ("lockdep: Enable PROVE_RAW_LOCK_NESTING with PROVE_LOCKING.") - Ccing Chris Bainbridge , author of the previous bug report. Greetings, Mateusz