From nobody Wed Dec 17 07:24:41 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 84A0BE7E62E for ; Tue, 26 Sep 2023 12:10:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234531AbjIZMKI (ORCPT ); Tue, 26 Sep 2023 08:10:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42348 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230231AbjIZMKG (ORCPT ); Tue, 26 Sep 2023 08:10:06 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0ED19120 for ; Tue, 26 Sep 2023 05:09:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1695730157; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=jimOcMvQCcdItEjwgV6HXjLHWStYRcQsZMjaE32LDyE=; b=e2YN7FhzhG9Uk06AOc7G3spKkNhhOyi/9fq1aAS10QfG2Ga2oe6RrUBVzVwrH8OrukMssf QscCTWVbFVLQr90tb1KriSwQMl8NbJ5SfDYhlP8kevhcmYfC9enReXdQFuQ+VLeHvcuKvP DnptCk9u2DS/9brvgwn3OIXNVYZppoI= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-360-ilM1DyNsNf--dzhCtfc2KA-1; Tue, 26 Sep 2023 08:09:12 -0400 X-MC-Unique: ilM1DyNsNf--dzhCtfc2KA-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 52ACA1C0CCAD; Tue, 26 Sep 2023 12:09:12 +0000 (UTC) Received: from MiWiFi-R3L-srv.redhat.com (unknown [10.72.112.19]) by smtp.corp.redhat.com (Postfix) with ESMTP id 3EA09140E950; Tue, 26 Sep 2023 12:09:07 +0000 (UTC) From: Baoquan He To: linux-kernel@vger.kernel.org Cc: kexec@lists.infradead.org, akpm@linux-foundation.org, eric.devolder@oracle.com, vschneid@redhat.com, sourabhjain@linux.ibm.com, Baoquan He Subject: [PATCH v3] Crash: add lock to serialize crash hotplug handling Date: Tue, 26 Sep 2023 20:09:05 +0800 Message-ID: <20230926120905.392903-1-bhe@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.7 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Eric reported that handling corresponding crash hotplug event can be failed easily when many memory hotplug event are notified in a short period. They failed because failing to take __kexec_lock. =3D=3D=3D=3D=3D=3D=3D [ 78.714569] Fallback order for Node 0: 0 [ 78.714575] Built 1 zonelists, mobility grouping on. Total pages: 18178= 86 [ 78.717133] Policy zone: Normal [ 78.724423] crash hp: kexec_trylock() failed, elfcorehdr may be inaccura= te [ 78.727207] crash hp: kexec_trylock() failed, elfcorehdr may be inaccura= te [ 80.056643] PEFILE: Unsigned PE binary =3D=3D=3D=3D=3D=3D=3D The memory hotplug events are notified very quickly and very many, while the handling of crash hotplug is much slower relatively. So the atomic variable __kexec_lock and kexec_trylock() can't guarantee the serialization of crash hotplug handling. Here, add a new mutex lock __crash_hotplug_lock to serialize crash hotplug handling specifically. This doesn't impact the usage of __kexec_lock. Signed-off-by: Baoquan He Reviewed-by: Eric DeVolder Reviewed-by: Valentin Schneider Tested-by: Eric DeVolder --- v2->v3: - crash_check_update_elfcorehdr() need take __crash_hotplug_lock too because there's tiny racing window when kexec_load interface is taken. Eric pointed out this. v1->v2: - Move mutex lock definition into CONFIG_CRASH_HOTPLUG ifdeffery scope in kernel/crash_core.c because the lock is only needed and used in that scope. Suggested by Eric. kernel/crash_core.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/kernel/crash_core.c b/kernel/crash_core.c index 03a7932cde0a..2f675ef045d4 100644 --- a/kernel/crash_core.c +++ b/kernel/crash_core.c @@ -739,6 +739,17 @@ subsys_initcall(crash_notes_memory_init); #undef pr_fmt #define pr_fmt(fmt) "crash hp: " fmt =20 +/* + * Different than kexec/kdump loading/unloading/jumping/shrinking which + * usually rarely happen, there will be many crash hotplug events notified + * during one short period, e.g one memory board is hot added and memory + * regions are online. So mutex lock __crash_hotplug_lock is used to + * serialize the crash hotplug handling specifically. + */ +DEFINE_MUTEX(__crash_hotplug_lock); +#define crash_hotplug_lock() mutex_lock(&__crash_hotplug_lock) +#define crash_hotplug_unlock() mutex_unlock(&__crash_hotplug_lock) + /* * This routine utilized when the crash_hotplug sysfs node is read. * It reflects the kernel's ability/permission to update the crash @@ -748,9 +759,11 @@ int crash_check_update_elfcorehdr(void) { int rc =3D 0; =20 + crash_hotplug_lock(); /* Obtain lock while reading crash information */ if (!kexec_trylock()) { pr_info("kexec_trylock() failed, elfcorehdr may be inaccurate\n"); + crash_hotplug_unlock(); return 0; } if (kexec_crash_image) { @@ -761,6 +774,7 @@ int crash_check_update_elfcorehdr(void) } /* Release lock now that update complete */ kexec_unlock(); + crash_hotplug_unlock(); =20 return rc; } @@ -783,9 +797,11 @@ static void crash_handle_hotplug_event(unsigned int hp= _action, unsigned int cpu) { struct kimage *image; =20 + crash_hotplug_lock(); /* Obtain lock while changing crash information */ if (!kexec_trylock()) { pr_info("kexec_trylock() failed, elfcorehdr may be inaccurate\n"); + crash_hotplug_unlock(); return; } =20 @@ -852,6 +868,7 @@ static void crash_handle_hotplug_event(unsigned int hp_= action, unsigned int cpu) out: /* Release lock now that update complete */ kexec_unlock(); + crash_hotplug_unlock(); } =20 static int crash_memhp_notifier(struct notifier_block *nb, unsigned long v= al, void *v) --=20 2.41.0