From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=113.46.200.225 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1792634468; b=b+4aqelNfKBxPce2oSwOdJTXcS4L857RfAT8+OxVxQU72R8fiOyO6EslO6VikI+2h5ga 1G/egWXrUza/oeuX6WMHauOUnVnUj8+smqOf1uOP5D3o5oyaFHptr9wEmBxGek6B7CAPY wGlVTGZpCJla9yNZi4NJZ97sZQ17MTytGcDUbYbxPRRPUhkyfldLhEpH/R56ARE3gP3TO ppnD61XPUgqjPOIxmyyFjJYQUs0XYl2kcQceV7Z8yMLz5aWEU2qMDrWxRRZFfucEPyTOt KkJVpPXu26pYL7APeN8jEOKFl8EMM0v4p5/F/880JoLlDdDzc0aRBrKSR1IJZJ/slKA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792634468; h=DMARC-Filter:dkim-signature:Received:Received:Received:Message-ID: Date:MIME-Version:User-Agent:Subject:To:CC:References:From: In-Reply-To:Content-Type:Content-Transfer-Encoding:X-Originating-IP: X-ClientProxiedBy; bh=loBgwUbLOnAAak0q9uGjIQKEwQ4a4j4TVh8P+20MXEg=; b=TsW8l/UCyh5OCp5iA7oqWRwA/AO4TZbKsSBOLLMWEDfNQzxhd0b8B14UgtMBMkbqLtlu Cm7R4nq8lWZOpIIWoWD026uWUXTYRbUZez4a7G5Db7dMl6BcIoIYQI2eNcs/jxGUKe1x/ w4AXVadi06pxer6TndPgFkFzm0cpA4Yjs+gib2RwGchAAN9NCx0avMtOfEea9BqwANtDv 3MneyhycFPubfMk2A2wgjbJyEIjhqjaXzGzmp/P+unCZoZnp+8I4hisEK7hlQOsNqXRn1 zqkUchWnOSaubRYQ5+KSkcF8q+vNMfuDr5/h3GveeJzU3nX4L6tkyelW4q8ifDCpsew== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; dkim=pass header.d=huawei.com header.i=@huawei.com header.a=rsa-sha256 header.s=dkim header.b=Q+4ivRAN; arc=none smtp.remote-ip=113.46.200.225 Received: from canpmsgout10.his.huawei.com (canpmsgout10.his.huawei.com [113.46.200.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DBDB8606A31A; Thu, 22 Oct 2026 02:01:05 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org DBDB8606A31A 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, unprotected) header.d=huawei.com header.i=@huawei.com header.a=rsa-sha256 header.s=dkim header.b=Q+4ivRAN dkim-signature: v=1; a=rsa-sha256; d=huawei.com; s=dkim; c=relaxed/relaxed; q=dns/txt; h=From; bh=loBgwUbLOnAAak0q9uGjIQKEwQ4a4j4TVh8P+20MXEg=; b=Q+4ivRANcgbbFZT+RuqnOmzfQRgx/LVfmZmJnBznw3aijzTfLqiAXmQFPpHZ4wQr5N/a+UnSk 9QkwZygXGFsy6k2d0kw287r6cGCOPL2MK5xfPM3ACXVTWwq6O1+K0stbkZqxhIDb9q0MkhN+DRw UTGHL86gM/CDOpMtrrbG38U= Received: from mail.maildlp.com (unknown [172.19.163.200]) by canpmsgout10.his.huawei.com (SkyGuard) with ESMTPS id 4j98WL5Vhfz1K972; Thu, 22 Oct 2026 10:00:46 +0800 (CST) Received: from kwepemk200008.china.huawei.com (unknown [7.202.194.74]) by mail.maildlp.com (Postfix) with ESMTPS id 2FEAB40563; Thu, 22 Oct 2026 10:00:51 +0800 (CST) Received: from [10.67.110.68] (10.67.110.68) by kwepemk200008.china.huawei.com (7.202.194.74) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.45; Thu, 22 Oct 2026 10:00:49 +0800 Message-ID: <31d63208-3ef2-420f-a0c2-d9d6d49c5e21@huawei.com> Date: Thu, 22 Oct 2026 10:00:49 +0800 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v9 3/8] crash_core: serialize crash header preparation against hotplug To: Wandun , , , , CC: , , , , , , , , , , , , , , , , , , , , , , , , , , , , References: <20261021083011.2170525-1-chenwandun1@gmail.com> <20261021083011.2170525-4-chenwandun1@gmail.com> <12e4e687-1ff0-41b2-bdf8-7f48b29e1f2f@huawei.com> From: Jinjie Ruan In-Reply-To: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-ClientProxiedBy: kwepems200001.china.huawei.com (7.221.188.67) To kwepemk200008.china.huawei.com (7.202.194.74) 在 2026/10/21 17:48, Wandun 写道: > > > On 10/21/26 17:13, Jinjie Ruan wrote: >> >> >> 在 2026/10/21 16:30, Wandun Chen 写道: >>> From: Wandun Chen >>> >>> crash_prepare_headers() counts memory ranges before populating the >>> allocated crash_mem array. The weak implementation used by ARM64, >>> RISC-V and LoongArch walks memblock.memory, while x86 performs the same >>> two-pass operation over system RAM resources. Concurrent memory hotplug >>> can change range source between the two walks and make the populate >>> pass overflow cmem->ranges. >>> >>> Take device_hotplug_lock when preparing crash headers during >>> kexec_file_load(). The x86/riscv memory hotplug path already takes >>> device_hotplug_lock, so call __crash_prepare_headers() directly >>> to avoid recursive locking. >>> >>> Sashiko reported this issue in [1]. >>> >>> Fixes: 3751e728cef2 ("arm64: kexec_file: add crash dump support") >>> Fixes: 1bcca8620a91 ("LoongArch: Add crash dump support for kexec_file") >>> Fixes: 8acea455fafa ("RISC-V: Support for kexec_file on panic") >>> Fixes: dd5f726076cc ("kexec: support for kexec on panic using new system call") >>> Signed-off-by: Wandun Chen >>> Link: https://sashiko.dev/#/message/20260806101002.1F84E1F000E9@smtp.kernel.org [1] >>> Acked-by: Baoquan He >>> --- >>> arch/riscv/kernel/crash.c | 2 +- >>> arch/x86/kernel/crash.c | 2 +- >>> include/linux/crash_core.h | 2 ++ >>> kernel/crash_core.c | 17 +++++++++++++++-- >>> 4 files changed, 19 insertions(+), 4 deletions(-) >>> >>> diff --git a/arch/riscv/kernel/crash.c b/arch/riscv/kernel/crash.c >>> index fe5a4b306aae..ac8df2edf2a7 100644 >>> --- a/arch/riscv/kernel/crash.c >>> +++ b/arch/riscv/kernel/crash.c >>> @@ -70,7 +70,7 @@ void arch_crash_handle_hotplug_event(struct kimage *image, void *arg) >>> * Create the new elfcorehdr reflecting the changes to CPU and/or >>> * memory resources. >>> */ >>> - if (crash_prepare_headers(true, &elfbuf, &elfsz, NULL)) { >>> + if (__crash_prepare_headers(true, &elfbuf, &elfsz, NULL)) { >>> pr_err("unable to create new elfcorehdr"); >>> goto out; >>> } >>> diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c >>> index e6f23933a6df..bef008a0cb22 100644 >>> --- a/arch/x86/kernel/crash.c >>> +++ b/arch/x86/kernel/crash.c >>> @@ -465,7 +465,7 @@ void arch_crash_handle_hotplug_event(struct kimage *image, void *arg) >>> * Create the new elfcorehdr reflecting the changes to CPU and/or >>> * memory resources. >>> */ >>> - if (crash_prepare_headers(IS_ENABLED(CONFIG_X86_64), &elfbuf, &elfsz, NULL)) { >>> + if (__crash_prepare_headers(IS_ENABLED(CONFIG_X86_64), &elfbuf, &elfsz, NULL)) { >>> pr_err("unable to create new elfcorehdr"); >>> goto out; >>> } >>> diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h >>> index bc087124cd78..28e7a81cf263 100644 >>> --- a/include/linux/crash_core.h >>> +++ b/include/linux/crash_core.h >>> @@ -61,6 +61,8 @@ extern int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_ma >>> void **addr, unsigned long *sz); >>> extern int crash_prepare_headers(int need_kernel_map, void **addr, >>> unsigned long *sz, unsigned long *nr_mem_ranges); >>> +int __crash_prepare_headers(int need_kernel_map, void **addr, unsigned long *sz, >>> + unsigned long *nr_mem_ranges); >>> extern int crash_exclude_core_ranges(struct crash_mem **cmem); >>> >>> struct kimage; >>> diff --git a/kernel/crash_core.c b/kernel/crash_core.c >>> index faa0f22dbb41..8a861a946e26 100644 >>> --- a/kernel/crash_core.c >>> +++ b/kernel/crash_core.c >>> @@ -16,6 +16,7 @@ >>> #include >>> #include >>> #include >>> +#include >>> #include >>> #include >>> #include >>> @@ -344,8 +345,8 @@ int crash_exclude_core_ranges(struct crash_mem **cmem) >>> return 0; >>> } >>> >>> -int crash_prepare_headers(int need_kernel_map, void **addr, unsigned long *sz, >>> - unsigned long *nr_mem_ranges) >>> +int __crash_prepare_headers(int need_kernel_map, void **addr, unsigned long *sz, >>> + unsigned long *nr_mem_ranges) >>> { >>> unsigned int max_nr_ranges; >>> struct crash_mem *cmem; >>> @@ -382,6 +383,18 @@ int crash_prepare_headers(int need_kernel_map, void **addr, unsigned long *sz, >>> return ret; >>> } >>> >>> +int crash_prepare_headers(int need_kernel_map, void **addr, unsigned long *sz, >>> + unsigned long *nr_mem_ranges) >>> +{ >>> + int ret; >>> + >>> + lock_device_hotplug(); >>> + ret = __crash_prepare_headers(need_kernel_map, addr, sz, nr_mem_ranges); >>> + unlock_device_hotplug(); >> >> I think this patch conflicts with my changes and would also conflict >> with the implementation of arm64 crash hotplug. >> >> https://lore.kernel.org/all/20260921090450.807575-15-ruanjinjie@huawei.com/ >> > Have these patches already been merged? My current work is based on the latest > linux-next. If they have already been merged into the maintainer's branch, > please let me know, I will update my tree and rebase/re-adapt my changes accordingly. > > > Also, regarding the changes in kernel/crash_core.c: it looks like we modified > the same spot, the change is not wrong, is that right? Hi Wandun, However, I think someone should have informed me in advance; otherwise, doing duplicate fix work is pointless. I see that part of your patch series modifies code I previously changed, but I was not CC'd. > >> arm64 crash hotplug: >> https://lore.kernel.org/all/20260918100442.3841135-18-ruanjinjie@huawei.com/ > > In addition, if arm64 gains crash hotplug support, the code there would indeed > need to be modified (to avoid a deadlock). As of now, arm64 crash hotplug > support has not been merged yet either, has it? I just want to make sure I > haven't missed anything. Yes, you are right. If your patch series will be merged soon, I will develop based on it. > >> >>> + >>> + return ret; >>> +} >>> + >>> /** >>> * crash_exclude_mem_range - exclude a mem range for existing ranges >>> * @mem: mem->range contains an array of ranges sorted in ascending order >> > -- Best regards, Jinjie