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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 75C90C25B06 for ; Mon, 15 Aug 2022 02:01:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229841AbiHOCBE (ORCPT ); Sun, 14 Aug 2022 22:01:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39502 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229614AbiHOCBE (ORCPT ); Sun, 14 Aug 2022 22:01:04 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E61069590 for ; Sun, 14 Aug 2022 19:01:02 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 8B1E7B80C92 for ; Mon, 15 Aug 2022 02:01:01 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2736BC433C1; Mon, 15 Aug 2022 02:01:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1660528860; bh=XDB6S6/ea9m21s/4KN06Dzr/6MpfDa8emBSwuEKmEIw=; h=Date:To:From:Subject:From; b=1wlzSlBD9p7tAdYCAJJk7XYLCOI2s7Yc5nH99VkG2cxPCbIgGvLtpQflWEjveHqfz dSxnWwkKf6yZ1D9p/ZNNb3xxVqoSxRueCRfyjTelZps3f+2NxmlSo/iSOXdah03HHJ owQNDGBcLotag1+nV3K6qH6rPEaaXS6ixvZgNn2A= Date: Sun, 14 Aug 2022 19:00:58 -0700 To: mm-commits@vger.kernel.org, tglx@linutronix.de, pmladek@suse.com, linmiaohe@huawei.com, lgoncalv@redhat.com, jlelli@redhat.com, ebiederm@xmission.com, bigeasy@linutronix.de, bhe@redhat.com, arnd@arndb.de, vschneid@redhat.com, akpm@linux-foundation.org From: Andrew Morton Subject: + kexec-turn-all-kexec_mutex-acquisitions-into-trylocks.patch added to mm-nonmm-unstable branch Message-Id: <20220815020100.2736BC433C1@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org The patch titled Subject: kexec: turn all kexec_mutex acquisitions into trylocks has been added to the -mm mm-nonmm-unstable branch. Its filename is kexec-turn-all-kexec_mutex-acquisitions-into-trylocks.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kexec-turn-all-kexec_mutex-acquisitions-into-trylocks.patch This patch will later appear in the mm-nonmm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Valentin Schneider Subject: kexec: turn all kexec_mutex acquisitions into trylocks Date: Thu, 30 Jun 2022 23:32:57 +0100 Patch series "kexec, panic: Making crash_kexec() NMI safe", v4. This patch (of 2): Most acquistions of kexec_mutex are done via mutex_trylock() - those were a direct "translation" from: 8c5a1cf0ad3a ("kexec: use a mutex for locking rather than xchg()") there have however been two additions since then that use mutex_lock(): crash_get_memory_size() and crash_shrink_memory(). A later commit will replace said mutex with an atomic variable, and locking operations will become atomic_cmpxchg(). Rather than having those mutex_lock() become while (atomic_cmpxchg(&lock, 0, 1)), turn them into trylocks that can return -EBUSY on acquisition failure. This does halve the printable size of the crash kernel, but that's still neighbouring 2G for 32bit kernels which should be ample enough. Link: https://lkml.kernel.org/r/20220630223258.4144112-1-vschneid@redhat.com Link: https://lkml.kernel.org/r/20220630223258.4144112-2-vschneid@redhat.com Signed-off-by: Valentin Schneider Cc: Arnd Bergmann Cc: "Eric W . Biederman" Cc: Juri Lelli Cc: Luis Claudio R. Goncalves Cc: Miaohe Lin Cc: Petr Mladek Cc: Sebastian Andrzej Siewior Cc: Thomas Gleixner Cc: Baoquan He Signed-off-by: Andrew Morton --- include/linux/kexec.h | 2 +- kernel/kexec_core.c | 12 ++++++++---- kernel/ksysfs.c | 7 ++++++- 3 files changed, 15 insertions(+), 6 deletions(-) --- a/include/linux/kexec.h~kexec-turn-all-kexec_mutex-acquisitions-into-trylocks +++ a/include/linux/kexec.h @@ -427,7 +427,7 @@ extern int kexec_load_disabled; extern bool kexec_in_progress; int crash_shrink_memory(unsigned long new_size); -size_t crash_get_memory_size(void); +ssize_t crash_get_memory_size(void); #ifndef arch_kexec_protect_crashkres /* --- a/kernel/kexec_core.c~kexec-turn-all-kexec_mutex-acquisitions-into-trylocks +++ a/kernel/kexec_core.c @@ -1004,13 +1004,16 @@ void crash_kexec(struct pt_regs *regs) } } -size_t crash_get_memory_size(void) +ssize_t crash_get_memory_size(void) { - size_t size = 0; + ssize_t size = 0; + + if (!mutex_trylock(&kexec_mutex)) + return -EBUSY; - mutex_lock(&kexec_mutex); if (crashk_res.end != crashk_res.start) size = resource_size(&crashk_res); + mutex_unlock(&kexec_mutex); return size; } @@ -1022,7 +1025,8 @@ int crash_shrink_memory(unsigned long ne unsigned long old_size; struct resource *ram_res; - mutex_lock(&kexec_mutex); + if (!mutex_trylock(&kexec_mutex)) + return -EBUSY; if (kexec_crash_image) { ret = -ENOENT; --- a/kernel/ksysfs.c~kexec-turn-all-kexec_mutex-acquisitions-into-trylocks +++ a/kernel/ksysfs.c @@ -105,7 +105,12 @@ KERNEL_ATTR_RO(kexec_crash_loaded); static ssize_t kexec_crash_size_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { - return sprintf(buf, "%zu\n", crash_get_memory_size()); + ssize_t size = crash_get_memory_size(); + + if (size < 0) + return size; + + return sprintf(buf, "%zd\n", size); } static ssize_t kexec_crash_size_store(struct kobject *kobj, struct kobj_attribute *attr, _ Patches currently in -mm which might be from vschneid@redhat.com are kexec-turn-all-kexec_mutex-acquisitions-into-trylocks.patch panic-kexec-make-__crash_kexec-nmi-safe.patch