linux-kernel - [PATCH] perf/x86: Avoid kfree() in CPU

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Message-Id: <1350281023-9262-1-git-send-email-zheng.z.yan@intel.com>
Date:	Mon, 15 Oct 2012 14:03:43 +0800
From:	"Yan, Zheng" <zheng.z.yan@...el.com>
To:	peterz@...radead.org, tglx@...utronix.de, eranian@...gle.com,
	mingo@...nel.org, linux-kernel@...r.kernel.org
Cc:	"Yan, Zheng" <zheng.z.yan@...el.com>
Subject: [PATCH] perf/x86: Avoid kfree() in CPU_{STARTING,DYING}

From: "Yan, Zheng" <zheng.z.yan@...el.com>

On -rt kfree() can schedule, but CPU_{STARTING,DYING} should be
atomic. So use a list to defer kfree until CPU_{ONLINE,DEAD}.

Signed-off-by: Yan, Zheng <zheng.z.yan@...el.com>
---
 arch/x86/kernel/cpu/perf_event_intel_uncore.c | 27 ++++++++++++++++++++++++---
 1 file changed, 24 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event_intel_uncore.c b/arch/x86/kernel/cpu/perf_event_intel_uncore.c
index 99d96a4..6df0e60 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_uncore.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_uncore.c
@@ -2611,6 +2611,20 @@ static void __init uncore_pci_exit(void)
 	}
 }
 
+static LIST_HEAD(boxes_to_free);
+
+static void __cpuinit uncore_kfree_boxes(void)
+{
+	struct intel_uncore_box *box;
+
+	while (!list_empty(&boxes_to_free)) {
+		box = list_entry(boxes_to_free.next,
+				 struct intel_uncore_box, list);
+		list_del(&box->list);
+		kfree(box);
+	}
+}
+
 static void __cpuinit uncore_cpu_dying(int cpu)
 {
 	struct intel_uncore_type *type;
@@ -2625,7 +2639,7 @@ static void __cpuinit uncore_cpu_dying(int cpu)
 			box = *per_cpu_ptr(pmu->box, cpu);
 			*per_cpu_ptr(pmu->box, cpu) = NULL;
 			if (box && atomic_dec_and_test(&box->refcnt))
-				kfree(box);
+				list_add(&box->list, &boxes_to_free);
 		}
 	}
 }
@@ -2655,8 +2669,11 @@ static int __cpuinit uncore_cpu_starting(int cpu)
 				if (exist && exist->phys_id == phys_id) {
 					atomic_inc(&exist->refcnt);
 					*per_cpu_ptr(pmu->box, cpu) = exist;
-					kfree(box);
-					box = NULL;
+					if (box) {
+						list_add(&box->list,
+							 &boxes_to_free);
+						box = NULL;
+					}
 					break;
 				}
 			}
@@ -2795,6 +2812,10 @@ static int
 	case CPU_DYING:
 		uncore_cpu_dying(cpu);
 		break;
+	case CPU_ONLINE:
+	case CPU_DEAD:
+		uncore_kfree_boxes();
+		break;
 	default:
 		break;
 	}
-- 
1.7.11.7

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/