linux-kernel - [PATCH 2/3] x86/intel_rdt: Return state to default on umount

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Date:   Fri, 11 Nov 2016 17:02:37 -0800
From:   "Fenghua Yu" <fenghua.yu@...el.com>
To:     "Thomas Gleixner" <tglx@...utronix.de>
Cc:     "H. Peter Anvin" <h.peter.anvin@...el.com>,
        "Ingo Molnar" <mingo@...e.hu>, "Tony Luck" <tony.luck@...el.com>,
        "Ravi V Shankar" <ravi.v.shankar@...el.com>,
        "Sai Prakhya" <sai.praneeth.prakhya@...el.com>,
        "Vikas Shivappa" <vikas.shivappa@...ux.intel.com>,
        "linux-kernel" <linux-kernel@...r.kernel.org>,
        "x86" <x86@...nel.org>, "Fenghua Yu" <fenghua.yu@...el.com>
Subject: [PATCH 2/3] x86/intel_rdt: Return state to default on umount

From: Fenghua Yu <fenghua.yu@...el.com>

All CPUs in a rdtgroup are given back to the default rdtgroup
before the rdtgroup is removed during umount. After umount,
the default rdtgroup contains all online CPUs.

cpu_closid needs to be cleared for each cpu in root rdtgroup
during umount. Otherwise, PQR_ASSOC will be written to the
non-zero value stored in cpu_closid after next mount.

Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
---
 arch/x86/kernel/cpu/intel_rdt_rdtgroup.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
index cff286e..416b95e 100644
--- a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
+++ b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
@@ -801,6 +801,7 @@ static void rmdir_all_sub(void)
 {
 	struct rdtgroup *rdtgrp, *tmp;
 	struct task_struct *p, *t;
+	int cpu;
 
 	/* move all tasks to default resource group */
 	read_lock(&tasklist_lock);
@@ -819,10 +820,19 @@ static void rmdir_all_sub(void)
 		/* Remove each rdtgroup other than root */
 		if (rdtgrp == &rdtgroup_default)
 			continue;
+
+		/* Give any CPUs back to the default group */
+		cpumask_or(&rdtgroup_default.cpu_mask,
+			   &rdtgroup_default.cpu_mask, &rdtgrp->cpu_mask);
+
 		kernfs_remove(rdtgrp->kn);
 		list_del(&rdtgrp->rdtgroup_list);
 		kfree(rdtgrp);
 	}
+
+	for_each_cpu(cpu, &rdtgroup_default.cpu_mask)
+		per_cpu(cpu_closid, cpu) = 0;
+
 	kernfs_remove(kn_info);
 }
 
-- 
2.5.0