From mboxrd@z Thu Jan 1 00:00:00 1970 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 0AA03E7E62E for ; Tue, 26 Sep 2023 12:09:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:Message-ID:Date:Subject:Cc :To:From:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References: List-Owner; bh=cFqrd1QnX18KORy5ncYBt2Ijr1w11MswlHZ1WC1GnC8=; b=xYOcl3o4PAiYxE mfMMnsm9HTIriF12sbA6AkUIMwWhFhRn3MxjywXMYlbQbqJ+GUE2ZLg0sje7yW6yV2b1aTsk0sORW GJY27A4Rxtt9G8sbYyrzEF3GY5eyyHl5kUf+Uux6gRUfJRVaKGY67B3T/P553IzgBTqTUp47q/6xr FZb69KTXh64KMvWPMnBLWiUpB2FkXHOkKPvvKMjF04C8o7KR+l7xP/TxONBBilmfcKbRtSvB9bppm PuoukL0xmx3bYHkjIKeP7f8V5tX8h/JXtVDxMzrdag8oAVpSvLrloJjiITEWfz8nzM2voOysfNT8w b1gbYT5JGQGJNlQn8NMA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1ql6sV-00GKgE-1A; Tue, 26 Sep 2023 12:09:23 +0000 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1ql6sR-00GKdf-1A for kexec@lists.infradead.org; Tue, 26 Sep 2023 12:09:21 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1695730156; 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=H2ZFiN9n+2lQoNoY9m+OeSLJJcomCC5Ka2XiSf0bnd+M9PnpCf+1hbOTrp6V909PwQ9tFz OR+uinXiEDiBIWLB3xn+A8tNEHj180sGFVSt9aJnEpq9HOOt1RNhLR/YcTLXV0bz9YfpRq kVS/rdC2ZrBauuT4JfK7IipqKhCSbag= 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 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.7 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230926_050919_912728_338D0E6F X-CRM114-Status: GOOD ( 13.69 ) X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+kexec=archiver.kernel.org@lists.infradead.org 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. ======= [ 78.714569] Fallback order for Node 0: 0 [ 78.714575] Built 1 zonelists, mobility grouping on. Total pages: 1817886 [ 78.717133] Policy zone: Normal [ 78.724423] crash hp: kexec_trylock() failed, elfcorehdr may be inaccurate [ 78.727207] crash hp: kexec_trylock() failed, elfcorehdr may be inaccurate [ 80.056643] PEFILE: Unsigned PE binary ======= 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 --- 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 +/* + * 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 = 0; + 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(); return rc; } @@ -783,9 +797,11 @@ static void crash_handle_hotplug_event(unsigned int hp_action, unsigned int cpu) { struct kimage *image; + 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; } @@ -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(); } static int crash_memhp_notifier(struct notifier_block *nb, unsigned long val, void *v) -- 2.41.0 _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec