From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailout1.w1.samsung.com (mailout1.w1.samsung.com [210.118.77.11]) (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 6CC713CB2D7 for ; Mon, 8 Jun 2026 14:15:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=210.118.77.11 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780928113; cv=none; b=tmSW0AYdfg5FDUV2/5+aLLpdegj9NBdston68SxgBN8jcSFJEaQnyy4LGOUrY+p3bcaWdw6ItH7hhZ5N6BanlnxSM9EDhcK+iw3I+dzuQk4TJoUUUBW+efxwj393d7nxwxcxkmhJT5aLyJDR+qqJXtUABfbf0bAEgsdy3083LXM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780928113; c=relaxed/simple; bh=6M/oe/zzclJwh15lSs3rWJr3WUsdAGEM77I+HQGYLJ8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:From:In-Reply-To: Content-Type:References; b=LpsRzXp/K2VX4o3H8RNO2VSvR4oJzbFwnLREHnYiFFBPVqwZStO3xTbmaGap7E7vrfodaff7ytQU6vzBEq9SF3RZIQoJTT/IWz7c0D2pDY23q6DKFShnM0Ntq1RFjM5tpXUdQeKnU/iVOqrx0kUxfeKkViT/0h8JS+Ro2v/UZ8g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=samsung.com; spf=pass smtp.mailfrom=samsung.com; dkim=pass (1024-bit key) header.d=samsung.com header.i=@samsung.com header.b=MAigtQbb; arc=none smtp.client-ip=210.118.77.11 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=samsung.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=samsung.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=samsung.com header.i=@samsung.com header.b="MAigtQbb" Received: from eucas1p1.samsung.com (unknown [182.198.249.206]) by mailout1.w1.samsung.com (KnoxPortal) with ESMTP id 20260608141508euoutp01ffd68ad7051fa3a53b4991c00a7ebaca~3IK2_Wln41133611336euoutp01u for ; Mon, 8 Jun 2026 14:15:08 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 mailout1.w1.samsung.com 20260608141508euoutp01ffd68ad7051fa3a53b4991c00a7ebaca~3IK2_Wln41133611336euoutp01u DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=samsung.com; s=mail20170921; t=1780928108; bh=him0K+NtK6lv5Phq5fEw5VdeCYwjBK4w6Z04LJKy9e8=; h=Date:Subject:To:Cc:From:In-Reply-To:References:From; b=MAigtQbbGXQNg8QInumYS7ENZkBpfFLANGJhOWvsXOq6oWkDF0VFD4u1IaenIG17D m1WiXAj49HNxOxqX146BdIe57vAIHfrxZF3qCle3Zvc7I6cHr88QM7wiP9RNrHPlx/ eenHr18Q/nfTiA+FGIfyBpGnq3wZ8pZNHj6VNMHM= Received: from eusmtip2.samsung.com (unknown [203.254.199.222]) by eucas1p2.samsung.com (KnoxPortal) with ESMTPA id 20260608141507eucas1p278093770ade1e19d5400ea81bc191857~3IK2vh98t0309903099eucas1p2v; Mon, 8 Jun 2026 14:15:07 +0000 (GMT) Received: from [106.210.134.192] (unknown [106.210.134.192]) by eusmtip2.samsung.com (KnoxPortal) with ESMTPA id 20260608141507eusmtip27d23d88b1bfc950ccc8880e1f520cee2~3IK2ftRVJ2645226452eusmtip2R; Mon, 8 Jun 2026 14:15:07 +0000 (GMT) Message-ID: <904ced49-53e4-4f3e-977b-c4ea7c230bc5@samsung.com> Date: Mon, 8 Jun 2026 16:15:06 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Betterbird (Windows) Subject: Re: [PATCH 1/2] timers/migration: Fix hotplug migrator selection target on asymetric capacity machines To: Frederic Weisbecker Cc: Thomas Gleixner , LKML , Anna-Maria Behnsen Content-Language: en-US From: Marek Szyprowski In-Reply-To: Content-Transfer-Encoding: 8bit X-CMS-MailID: 20260608141507eucas1p278093770ade1e19d5400ea81bc191857 X-Msg-Generator: CA Content-Type: text/plain; charset="utf-8" X-RootMTR: 20260608094538eucas1p1b87572e8b8af819ccb1537c38cd51957 X-EPHeader: CA X-CMS-RootMailID: 20260608094538eucas1p1b87572e8b8af819ccb1537c38cd51957 References: <20260519220926.63437-1-frederic@kernel.org> <20260519220926.63437-2-frederic@kernel.org> <928989ef-8cca-4956-aeb6-3cfe5a74785c@samsung.com> On 08.06.2026 16:04, Frederic Weisbecker wrote: > Le Mon, Jun 08, 2026 at 11:45:37AM +0200, Marek Szyprowski a écrit : >> On 20.05.2026 00:09, Frederic Weisbecker wrote: >>> When a top-level migrator is deactivated, either at CPU down hotplug >>> time or when a CPU is domain isolated, a new migrator is elected among >>> the available CPUs and woken up to take over the migration duty. >>> >>> However that election must happen at the scope of a given hierarchy and >>> not globally, which the introduction of per-capacity hierarchies failed >>> to handle. >>> >>> As a result a given hierarchy may end up without migrator to handle >>> global timers. >>> >>> Fix it with making sure that the new migrator belongs to the same >>> hierarchy as the outgoing CPU. >>> >>> Fixes: 098cbaad8e57 ("timers/migration: Split per-capacity hierarchies") >>> Signed-off-by: Frederic Weisbecker >> This patch landed recently in linux-next as commit e4a70f5fbd43 ("timers/migration: >> Fix hotplug migrator selection target on asymetric capacity machines"). In my tests >> I found that it breaks system suspend/resume on some legacy big.LITTLE ARM machines. >> >> >> Reverting $subject, together with dependent commit d4f198c13611 ("timers/migration: >> Deactivate per-capacity hierarchies under nohz_full") on top of linux-next fixes >> this issue. Here is the log from the system suspend/resume failure introduced by >> the $subject patch: >> >> >> root@target:~# time rtcwake -s10 -mmem >> rtcwake: wakeup from "mem" using /dev/rtc0 at Mon Jun  8 11:17:23 2026 >> PM: suspend entry (deep) >> Filesystems sync: 0.000 seconds >> Freezing user space processes >> Freezing user space processes completed (elapsed 0.002 seconds) >> OOM killer disabled. >> Freezing remaining freezable tasks >> Freezing remaining freezable tasks completed (elapsed 0.042 seconds) >> printk: Suspending console(s) (use no_console_suspend to debug) >> ... >> Disabling non-boot CPUs ... >> ------------[ cut here ]------------ >> WARNING: kernel/time/timer_migration.c:1505 at >> tmigr_clear_cpu_available+0x3b8/0x3c8, CPU#5: cpuhp/5/40 > Thanks but which tree is this? The only warning I see there is on line 1521 > 1532 (tip:timers/core). > > It's probably line 1521 somehow. Is it possible that arch_scale_cpu_capacity() > returns a different result between CPU boot up and CPU down? The log has been captured on the kernel compiled from the e4a70f5fbd43 commit. Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland