From: Reinette Chatre <reinette.chatre@intel.com>
To: Chen Yu <yu.c.chen@intel.com>, <tony.luck@intel.com>
Cc: <x86@kernel.org>, <linux-kernel@vger.kernel.org>,
<tglx@kernel.org>, <bp@alien8.de>, <mingo@redhat.com>,
<dave.hansen@linux.intel.com>, <hpa@zytor.com>,
<fenghuay@nvidia.com>, <babu.moger@amd.com>,
<anil.keshavamurthy@broadcom.com>, <chen.yu@linux.dev>,
Hongyu Ning <hongyu.ning@linux.intel.com>
Subject: Re: [PATCH v5 08/10] fs/resctrl: Do not invoke smp_processor_id() in preemptible context
Date: Fri, 10 Jul 2026 16:48:09 -0700 [thread overview]
Message-ID: <f8a66ddf-8696-49ac-83c3-fa6f364949e3@intel.com> (raw)
In-Reply-To: <cd5e7dbc58230498e5c31e362a0e4110924b8fef.1782866200.git.yu.c.chen@intel.com>
Hi Chenyu,
On 7/1/26 6:47 AM, Chen Yu wrote:
> From: Tony Luck <tony.luck@intel.com>
>
> Currently, mon_evt::any_cpu is false for all events associated with
> RDT_RESOURCE_L3. The MMIO-based CMT will set any_cpu to true in a
> follow-up patch. This change will trigger a warning when calling
Please drop the "in a follow-up patch" since that becomes irrelevant after
merge. Also please rewrite this paragraph to not just describe code but
what this actually means at a high level.
> smp_processor_id() inside __l3_mon_event_count(), because
> __l3_mon_event_count() may be invoked from arbitrary CPUs in task
> context. Since the calling context is preemptible here,
> smp_processor_id() will emit a debug warning.
>
> To prepare for MMIO-based CMT reads, skip the current CPU lookup
> when an event's any_cpu flag is set. Events with this flag do not
> require execution on a specific CPU.
Please note there is an upcoming change that will impact this change.
Nothing major, the change should be clear.
https://lore.kernel.org/lkml/6b3c66a49788828bd8c04a6911bd74c91ccd56f3.1782857711.git.reinette.chatre@intel.com/
Reinette
next prev parent reply other threads:[~2026-07-10 23:48 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-01 13:44 [PATCH v5 00/10] Introduce MMIO-based CMT access for Enhanced RDT Chen Yu
2026-07-01 13:45 ` [PATCH v5 01/10] x86/resctrl: Require 64-bit x86 for resctrl support Chen Yu
2026-07-01 13:45 ` [PATCH v5 02/10] x86/topology: Export topo_lookup_cpuid() for resctrl use Chen Yu
2026-07-10 23:35 ` Reinette Chatre
2026-07-01 13:45 ` [PATCH v5 03/10] x86/resctrl: Parse ACPI ERDT table and save CACD cpumask for RMDD domains Chen Yu
2026-07-10 23:42 ` Reinette Chatre
2026-07-01 13:45 ` [PATCH v5 04/10] x86/resctrl: Attach ACPI ERDT information to L3 mon domain on CPU online Chen Yu
2026-07-10 23:45 ` Reinette Chatre
2026-07-01 13:46 ` [PATCH v5 05/10] x86/resctrl: Parse ACPI CMRC table Chen Yu
2026-07-10 23:46 ` Reinette Chatre
2026-07-01 13:46 ` [PATCH v5 06/10] x86/resctrl: Replace "msr" in monitoring data identifiers Chen Yu
2026-07-10 23:47 ` Reinette Chatre
2026-07-01 13:46 ` [PATCH v5 07/10] x86/resctrl: Refactor the monitor read function Chen Yu
2026-07-01 13:47 ` [PATCH v5 08/10] fs/resctrl: Do not invoke smp_processor_id() in preemptible context Chen Yu
2026-07-10 23:48 ` Reinette Chatre [this message]
2026-07-01 13:47 ` [PATCH v5 09/10] x86/resctrl: Introduce helpers to read L3 occupancy via MMIO Chen Yu
2026-07-10 23:53 ` Reinette Chatre
2026-07-01 13:47 ` [PATCH v5 10/10] x86/resctrl: Enable " Chen Yu
2026-07-10 23:55 ` Reinette Chatre
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