From nobody Mon Jun 8 23:58:18 2026 Received: from canpmsgout01.his.huawei.com (canpmsgout01.his.huawei.com [113.46.200.216]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A241019F12D; Mon, 25 May 2026 13:08:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=113.46.200.216 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779714538; cv=none; b=flfx38W6zCh8oFWv4FfBogen6DSH2f/boQyX/IHqDPpsv3VuxvHo2Upxi7Ql/ixJf7X3fSk2ZLMNIdWnLNOdi7PhiK/TfwlfR26Vk6tFNjBKLXiuHkXRmNZiJJoc/J7lwKnp6qG9R9eH61zHp9bTgXUikYK6fRL2QuAaRqhkpSg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779714538; c=relaxed/simple; bh=AJnfyEu0MJoCHaW2I0rVs9/A/GEGbBG4fseJWQwg2TQ=; h=From:To:CC:Subject:Date:Message-ID:MIME-Version:Content-Type; b=K4u077/MyysRucoa2zn5kSWIhvgjTrb6rJfSBBPmbxOpPqXHlPFdEpEaO9uLXGJ5crSUy3fyKTp8igdXYw6Zv0Me+JFGYqWUOKLAKrnoLjrBJ0ep47g3EwHAvr6tNtZq0BNaCCzD06Of+Ta3x33wOWglJALLFu2yAAkEPDmzNik= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; dkim=pass (1024-bit key) header.d=huawei.com header.i=@huawei.com header.b=hcM7a7x6; arc=none smtp.client-ip=113.46.200.216 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=huawei.com header.i=@huawei.com header.b="hcM7a7x6" dkim-signature: v=1; a=rsa-sha256; d=huawei.com; s=dkim; c=relaxed/relaxed; q=dns/txt; h=From; bh=BDZAkoMDZmk4/1OiDYc7l7h4pQDfCOhfv04SS9wg3Qg=; b=hcM7a7x6IokjQvg0XI0RP/SUxHTeA3OMvWqQ514oZVdxon0/YuwFJtOKkrjj0oEKRz7UWZbwS KaG60NfRgT6+wE9b0LwF9VFeusMSO5bS1W11ck2OYCbikKB+4OnTyNi29UhtszAuhyREq/BgSXj 6XYHsgEbIw11n8eyKsltNoc= Received: from mail.maildlp.com (unknown [172.19.163.0]) by canpmsgout01.his.huawei.com (SkyGuard) with ESMTPS id 4gPGGD2BGfz1T4Gw; Mon, 25 May 2026 21:00:52 +0800 (CST) Received: from dggpemf500011.china.huawei.com (unknown [7.185.36.131]) by mail.maildlp.com (Postfix) with ESMTPS id D6A6A40537; Mon, 25 May 2026 21:08:50 +0800 (CST) Received: from huawei.com (10.90.53.73) by dggpemf500011.china.huawei.com (7.185.36.131) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Mon, 25 May 2026 21:08:50 +0800 From: Jinjie Ruan To: , , CC: Subject: [PATCH] rtc: interface: Add rtc time jump debug in rtc_timer_do_work() Date: Mon, 25 May 2026 21:08:25 +0800 Message-ID: <20260525130825.954214-1-ruanjinjie@huawei.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: kwepems100002.china.huawei.com (7.221.188.206) To dggpemf500011.china.huawei.com (7.185.36.131) Content-Type: text/plain; charset="utf-8" In virtualization environments like QEMU [1], or during hardware clocksource anomalies, an extreme time-warp event can occur. When the system time abruptly jumps forward, the rtc_timer_do_work() handler falls into a prolonged processing loop to clear accumulated historical timers via timerqueue_getnext(). Running this loop indefinitely under the rtc->ops_lock mutex triggers a kernel softlockup, stalling the system. Introduce an adaptive telemetry and loop guard mechanism to enhance debug visibility and prevent softlockups: 1. Record `start_jiffies` upon entry and leverage `time_after()` to check if the loop has monopolized the CPU for more than 1s (HZ). If so, the handler prints a telemetry warning, triggers a WARN stack dump, and breaks the loop to safely yield the CPU. 2. Track the execution via a `loop_count` metric. Printing this counter in the warning log provides vital diagnostics to distinguish an aggressive time-warp storm (high count) from a bogged-down callback bug (low count). 3. Utilize the kernel format specifier `%ptR` to convert the raw ktime into a human-readable timestamp (YYYY-MM-DD HH:MM:SS), allowing developers to instantly pinpoint the exact boundary of the time jump in dmesg. This non-destructive telemetry guard provides precise hardware/emulator diagnostic visibility while ensuring core kernel availability. [1]: https://lore.kernel.org/all/20260114013257.3500578-1-ruanjinjie@huawei= .com/ Signed-off-by: Jinjie Ruan --- drivers/rtc/interface.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c index 1906f4884a83..f6c5fd16cc4e 100644 --- a/drivers/rtc/interface.c +++ b/drivers/rtc/interface.c @@ -927,10 +927,12 @@ static void rtc_timer_remove(struct rtc_device *rtc, = struct rtc_timer *timer) */ void rtc_timer_do_work(struct work_struct *work) { - struct rtc_timer *timer; + unsigned long start_jiffies =3D jiffies; struct timerqueue_node *next; - ktime_t now; + struct rtc_timer *timer; struct rtc_time tm; + int loop_count =3D 0; + ktime_t now; int err; =20 struct rtc_device *rtc =3D @@ -945,6 +947,15 @@ void rtc_timer_do_work(struct work_struct *work) } now =3D rtc_tm_to_ktime(tm); while ((next =3D timerqueue_getnext(&rtc->timerqueue))) { + loop_count++; + + if (unlikely(time_after(jiffies, start_jiffies + HZ))) { + dev_warn(&rtc->dev, "RTC time jump (loop: %d) to %ptR.\n", + loop_count, &tm); + WARN_ON_ONCE(1); + break; + } + if (next->expires > now) break; =20 --=20 2.34.1