From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.12]) (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 B6A7738D404 for ; Wed, 29 Jul 2026 17:28:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.12 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785346093; cv=none; b=qbrzpsHuAiwsFQ5OzfxfIDLdXs5fld7CVEiAUChHBaHbCc+Ot1LcmN4/nn//PSz4gYyn6f8op56QD6P38BUbKpAsF3raSZYHp+4IfRwRtx4F1WQ+VlrBan/y2AdYUDBHD5XQEoV8YuAkcLScN4iD50ySoJAex8Kvac3swQsgU9c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785346093; c=relaxed/simple; bh=mWVZEzDlZtNwUJUexPsoN8ix4vQboGhHSRMINCgPeY0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=a2HVRRK0keq1b1l/jTavNQE2gUJDoaAQsIUp3qvWAnOyOMtRTRe/OL1BkZZL6S7tN9tDtImelLfJTe1cf3UbpdaZhDny2RKJNskEVMj6AIXoW9qTA/ga0bbF4vbDotanykyI6maiNGJAvDeo0bpXXqO4++fB199wqnuyBzGvHUo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=P9G+yNTG; arc=none smtp.client-ip=198.175.65.12 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="P9G+yNTG" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1785346091; x=1816882091; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=mWVZEzDlZtNwUJUexPsoN8ix4vQboGhHSRMINCgPeY0=; b=P9G+yNTGy4LTvYJtXicopvS6huNePNg7Cg6vHCNCHGObKEMDxRVdICSv ehl7ZslLhaIFoDZKcBT0XVDAWWWYwnyhZ4RP6DzJ2RX9GE4RUewp71QoT 7IfZBefDqocpxpEMV7WQTGMSvV/Myn1K4BpBU0wXDeEe+rR/9jBWZmB9Q fuYeL5urYFnmszcf+MZiOMzjnm703xzZqbnPoDSGGLn2oAikawFmHcRYn tKyEb7ZQkbo0cM4rlLAiRp+AiEkProDH3HyKafUKuQzhuNjVWbeCpbuwI aI5j9zpobocYP1gBeaObgQbijbqZqMKBiDj38QnhrUD9iTkJuVrv/L6pt Q==; X-CSE-ConnectionGUID: Q6HAAc9qRP6+NjxAqD7+Kw== X-CSE-MsgGUID: ku94Swa8QmGh+1KNZJWCKw== X-IronPort-AV: E=McAfee;i="6800,10657,11859"; a="97473664" X-IronPort-AV: E=Sophos;i="6.25,192,1779174000"; d="scan'208";a="97473664" Received: from fmviesa004.fm.intel.com ([10.60.135.144]) by orvoesa104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Jul 2026 10:28:03 -0700 X-CSE-ConnectionGUID: TIir+1jVQIi7woYnDB+gOw== X-CSE-MsgGUID: LetGeuk8SDKUilw7OiKAew== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.25,192,1779174000"; d="scan'208";a="262024606" Received: from iherna2-mobl4.amr.corp.intel.com (HELO agluck-desk3.home.arpa) ([10.124.223.238]) by fmviesa004-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Jul 2026 10:28:02 -0700 From: Tony Luck To: Fenghua Yu , Reinette Chatre , Maciej Wieczor-Retman , Peter Newman , James Morse , Babu Moger , Drew Fustini , Dave Martin , Chen Yu , David E Box , x86@kernel.org Cc: Christoph Hellwig , linux-kernel@vger.kernel.org, patches@lists.linux.dev, Tony Luck Subject: [PATCH v10 12/17] x86/resctrl: Prepare to handle nested mount requests Date: Wed, 29 Jul 2026 10:27:47 -0700 Message-ID: <20260729172752.11561-13-tony.luck@intel.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260729172752.11561-1-tony.luck@intel.com> References: <20260729172752.11561-1-tony.luck@intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit There is no upper level serialization of mount(2) system calls. mount/unmount operations can happen in parallel with CPU hotplug events that need to add/remove files and directories when domains are added or removed. Use cpus_read_lock() plus mutex_lock(&domain_list_lock) to protect architecture code from races. Signed-off-by: Tony Luck --- v10: New patch include/linux/resctrl.h | 2 +- arch/x86/kernel/cpu/resctrl/core.c | 40 ++++++++++++++++++++++++------ drivers/resctrl/mpam_resctrl.c | 3 ++- 3 files changed, 35 insertions(+), 10 deletions(-) diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h index 568a650c0224..65245f2fdad0 100644 --- a/include/linux/resctrl.h +++ b/include/linux/resctrl.h @@ -579,7 +579,7 @@ void resctrl_offline_cpu(unsigned int cpu); * Architecture hook called at beginning of first file system mount attempt. * No locks are held. */ -void resctrl_arch_pre_mount(void); +int resctrl_arch_pre_mount(void); /* * Architecture hook called when mount fails, or on unmount. diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c index e335a143f3e5..906aa4dfc363 100644 --- a/arch/x86/kernel/cpu/resctrl/core.c +++ b/arch/x86/kernel/cpu/resctrl/core.c @@ -16,7 +16,6 @@ #define pr_fmt(fmt) "resctrl: " fmt -#include #include #include #include @@ -807,25 +806,47 @@ static int resctrl_arch_offline_cpu(unsigned int cpu) return 0; } -void resctrl_arch_pre_mount(void) +/* + * Linux provides no synchronization for mount(2) system calls. + * resctrl_arch_pre_mount() and resctrl_arch_unmount() are called + * with no locks held. Mount/unmount may also race with CPU hotplug + * events that add/remove per-domain files and directories. + * + * Use cpus_read_lock() plus domain_list_lock to protect operations. + * + * Keep track locally at the architecture level whether the file + * system is mounted (or in process of being mounted). + */ +static bool arch_mounted; + +int resctrl_arch_pre_mount(void) { struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_PERF_PKG].r_resctrl; + int ret = -EBUSY; int cpu; + cpus_read_lock(); + mutex_lock(&domain_list_lock); + if (arch_mounted) + goto unlock; + arch_mounted = true; + ret = 0; + if (!intel_aet_pre_mount()) - return; + goto unlock; /* * Late discovery of telemetry events means the domains for the * resource were not built. Do that now. */ - cpus_read_lock(); - mutex_lock(&domain_list_lock); r->mon_capable = true; for_each_online_cpu(cpu) domain_add_cpu_mon(cpu, r); +unlock: mutex_unlock(&domain_list_lock); cpus_read_unlock(); + + return ret; } void resctrl_arch_unmount(void) @@ -833,16 +854,19 @@ void resctrl_arch_unmount(void) struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_PERF_PKG].r_resctrl; int cpu; + cpus_read_lock(); + mutex_lock(&domain_list_lock); + arch_mounted = false; + if (!r->mon_capable) - return; + goto unlock; intel_aet_unmount(); - cpus_read_lock(); - mutex_lock(&domain_list_lock); for_each_online_cpu(cpu) domain_remove_cpu_mon(cpu, r); r->mon_capable = false; +unlock: mutex_unlock(&domain_list_lock); cpus_read_unlock(); } diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c index 5859cc0f5e37..71125779484f 100644 --- a/drivers/resctrl/mpam_resctrl.c +++ b/drivers/resctrl/mpam_resctrl.c @@ -158,8 +158,9 @@ bool resctrl_arch_get_io_alloc_enabled(struct rdt_resource *r) return false; } -void resctrl_arch_pre_mount(void) +int resctrl_arch_pre_mount(void) { + return 0; } void resctrl_arch_unmount(void) -- 2.55.0