linux-kernel - [PATCH 2/2] x86/intel_rdt: Fix bug in initialization, locks and write cbm mask.

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Message-Id: <1446689969-67703-2-git-send-email-davidcc@google.com>
Date:	Wed,  4 Nov 2015 18:19:29 -0800
From:	David Carrillo-Cisneros <davidcc@...gle.com>
To:	Fenghua Yu <fenghua.yu@...el.com>
Cc:	Stephane Eranian <eranian@...gle.com>,
	Paul Turner <pjt@...gle.com>, linux-kernel@...r.kernel.org,
	David Carrillo-Cisneros <davidcc@...gle.com>
Subject: [PATCH 2/2] x86/intel_rdt: Fix bug in initialization, locks and write cbm mask.

Fix bugs in patch series "x86:Intel Cache Allocation Technology Support"
patches by Fenghua Yu. Changes are:
  1) Instruct task_css_check not to print a warning for
    unnecesary lockdeps when calling from __rdt_intel_sched_in
    since all callers are already synchronized by task_rq_lock().
  2) Add missing mutex_locks surrounding accesses to clos_cbm_table.
  3) Properly initialize online cpus in intel_rdt_late_init by using
    intel_rdt_cpu_start() instead of rdt_cpumask_update().
  4) Make cbm_validate_rdt_cgroup to actually use the children's mask
    when validating children's masks (as it should).

Signed-off-by: David Carrillo-Cisneros <davidcc@...gle.com>
---
 arch/x86/include/asm/intel_rdt.h | 12 +++++++++---
 arch/x86/kernel/cpu/intel_rdt.c  | 24 ++++++++++++++++++------
 2 files changed, 27 insertions(+), 9 deletions(-)

diff --git a/arch/x86/include/asm/intel_rdt.h b/arch/x86/include/asm/intel_rdt.h
index fbe1e00..f487a93 100644
--- a/arch/x86/include/asm/intel_rdt.h
+++ b/arch/x86/include/asm/intel_rdt.h
@@ -37,11 +37,17 @@ static inline struct intel_rdt *parent_rdt(struct intel_rdt *ir)
 }
 
 /*
- * Return rdt group to which this task belongs.
+ * Return rdt group to which this task belongs without checking for lockdep.
  */
-static inline struct intel_rdt *task_rdt(struct task_struct *task)
+static inline struct intel_rdt *task_rdt_nocheck(struct task_struct *task)
 {
-	return css_rdt(task_css(task, intel_rdt_cgrp_id));
+	/*
+	 * The checks for lockdep performed by task_subsys_state are not
+	 * necessary when callers are properly synchronized by other locks.
+	 * If the caller for this function is not properly synchronized
+	 * use task_css instead.
+	 */
+	return css_rdt(task_css_check(task, intel_rdt_cgrp_id, true));
 }
 
 /*
diff --git a/arch/x86/kernel/cpu/intel_rdt.c b/arch/x86/kernel/cpu/intel_rdt.c
index cb4d2ef..d5fa76f 100644
--- a/arch/x86/kernel/cpu/intel_rdt.c
+++ b/arch/x86/kernel/cpu/intel_rdt.c
@@ -115,7 +115,13 @@ static inline bool cache_alloc_supported(struct cpuinfo_x86 *c)
 void __intel_rdt_sched_in(void *dummy)
 {
 	struct intel_pqr_state *state = this_cpu_ptr(&pqr_state);
-	struct intel_rdt *ir = task_rdt(current);
+
+	/*
+	 * All callers are synchronized by task_rq_lock(); we do not use RCU
+	 * which is pointless here. Thus, we call task_rdt_nocheck that avoids
+	 * the lockdep checks.
+	 */
+	struct intel_rdt *ir = task_rdt_nocheck(current);
 
 	if (ir->closid == state->closid)
 		return;
@@ -403,7 +409,9 @@ static int intel_cache_alloc_cbm_read(struct seq_file *m, void *v)
 	struct intel_rdt *ir = css_rdt(seq_css(m));
 	unsigned long l3_cbm = 0;
 
+	mutex_lock(&rdt_group_mutex);
 	clos_cbm_table_read(ir->closid, &l3_cbm);
+	mutex_unlock(&rdt_group_mutex);
 	seq_printf(m, "%08lx\n", l3_cbm);
 
 	return 0;
@@ -431,7 +439,7 @@ static int cbm_validate_rdt_cgroup(struct intel_rdt *ir, unsigned long cbmvalue)
 	rcu_read_lock();
 	rdt_for_each_child(css, ir) {
 		c = css_rdt(css);
-		clos_cbm_table_read(par->closid, &cbm_tmp);
+		clos_cbm_table_read(c->closid, &cbm_tmp);
 		if (!bitmap_subset(&cbm_tmp, &cbmvalue, MAX_CBM_LENGTH)) {
 			rcu_read_unlock();
 			err = -EINVAL;
@@ -504,7 +512,6 @@ static int intel_cache_alloc_cbm_write(struct cgroup_subsys_state *css,
 	closcbm_map_dump();
 out:
 	mutex_unlock(&rdt_group_mutex);
-
 	return err;
 }
 
@@ -513,12 +520,16 @@ static void rdt_cgroup_init(void)
 	int max_cbm_len = boot_cpu_data.x86_cache_max_cbm_len;
 	u32 closid;
 
+	mutex_lock(&rdt_group_mutex);
+
 	closid_alloc(&closid);
 
 	WARN_ON(closid != 0);
 
 	rdt_root_group.closid = closid;
 	clos_cbm_table_update(closid, (1ULL << max_cbm_len) - 1);
+
+	mutex_unlock(&rdt_group_mutex);
 }
 
 static int __init intel_rdt_late_init(void)
@@ -552,15 +563,16 @@ static int __init intel_rdt_late_init(void)
 	cpu_notifier_register_begin();
 
 	for_each_online_cpu(i)
-		rdt_cpumask_update(i);
-
+		intel_rdt_cpu_start(i);
 	__hotcpu_notifier(intel_rdt_cpu_notifier, 0);
 
 	cpu_notifier_register_done();
+
 	rdt_cgroup_init();
 
 	static_key_slow_inc(&rdt_enable_key);
-	pr_info("Intel cache allocation enabled\n");
+	pr_info("Intel cache allocation enabled\n"
+		"max_closid:%u, max_cbm_len:%u\n", maxid, max_cbm_len);
 out_err:
 
 	return err;
-- 
2.6.0.rc2.230.g3dd15c0

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