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Date: Thu, 7 Aug 2014 10:05:45 -0500 (CDT)
From: Christoph Lameter <cl@...two.org>
To: Tejun Heo <htejun@...il.com>
cc: linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
Fengguang Wu <fengguang.wu@...el.com>,
Rusty Russell <rusty@...tcorp.com.au>,
Motohiro Kosaki <Motohiro.Kosaki@...fujitsu.com>,
Mike Travis <travis@....com>
Subject: percpu: Define this_cpu_cpumask_var_t_ptr
I think I finally found the source of the nasty failures of the
__get_cpu_var patchset:
Subject: __get_cpu_var/cpumask_var_t: Resolve ambiguities
__get_cpu_var can paper over differences in the definitions
of cpumask_var_t and either use the address of the cpumask
variable directly or perform a fetch of the address of the
struct cpumask allocated elsewhere. This is important
particularly when using per cpu cpumask_var_t declarations
because in one case we have an offset into a per cpu area
to handle and in the other case we need to fetch a pointer
from the offset.
This patch introduces a new macro
this_cpu_cpumask_var_t_ptr()
that is defined where cpumask_var_t is defined and performs
the proper actions. All use cases where __get_cpu_var
is used with cpumask_var_t are converted to the use
of this_cpu_cpumask_var_t_ptr().
Signed-off-by: Christoph Lameter <cl@...ux.com>
---
include/linux/kernel_stat.h | 4 ++--
kernel/events/callchain.c | 4 ++--
kernel/events/core.c | 24 ++++++++++++------------
kernel/sched/deadline.c | 2 +-
kernel/sched/fair.c | 2 +-
kernel/sched/rt.c | 2 +-
kernel/sched/sched.h | 4 ++--
kernel/taskstats.c | 2 +-
kernel/time/tick-sched.c | 4 ++--
kernel/user-return-notifier.c | 4 ++--
10 files changed, 26 insertions(+), 26 deletions(-)
Index: linux/include/linux/cpumask.h
===================================================================
--- linux.orig/include/linux/cpumask.h 2014-08-07 09:36:05.954916998 -0500
+++ linux/include/linux/cpumask.h 2014-08-07 09:55:38.732748680 -0500
@@ -666,10 +666,19 @@
*
* This code makes NR_CPUS length memcopy and brings to a memory corruption.
* cpumask_copy() provide safe copy functionality.
+ *
+ * Note that there is another evil here: If you define a cpumask_var_t
+ * as a percpu variable then the way to obtain the address of the cpumask
+ * structure differently influences what this_cpu_* operation needs to be
+ * used. Please use this_cpu_cpumask_var_t in those cases. The direct use
+ * of this_cpu_ptr() or this_cpu_read() will lead to failures when the
+ * other type of cpumask_var_t implementation is configured.
*/
#ifdef CONFIG_CPUMASK_OFFSTACK
typedef struct cpumask *cpumask_var_t;
+#define this_cpu_cpumask_var_t_ptr(x) this_cpu_read(x)
+
bool alloc_cpumask_var_node(cpumask_var_t *mask, gfp_t flags, int node);
bool alloc_cpumask_var(cpumask_var_t *mask, gfp_t flags);
bool zalloc_cpumask_var_node(cpumask_var_t *mask, gfp_t flags, int node);
@@ -681,6 +690,8 @@
#else
typedef struct cpumask cpumask_var_t[1];
+#define this_cpu_cpumask_var_t_ptr(x) this_cpu_ptr(&x)
+
static inline bool alloc_cpumask_var(cpumask_var_t *mask, gfp_t flags)
{
return true;
Index: linux/kernel/sched/deadline.c
===================================================================
--- linux.orig/kernel/sched/deadline.c 2014-08-07 09:36:05.954916998 -0500
+++ linux/kernel/sched/deadline.c 2014-08-07 09:36:05.902917978 -0500
@@ -1158,7 +1158,7 @@
static int find_later_rq(struct task_struct *task)
{
struct sched_domain *sd;
- struct cpumask *later_mask = __get_cpu_var(local_cpu_mask_dl);
+ struct cpumask *later_mask = this_cpu_cpumask_var_t_ptr(local_cpu_mask_dl);
int this_cpu = smp_processor_id();
int best_cpu, cpu = task_cpu(task);
Index: linux/kernel/sched/fair.c
===================================================================
--- linux.orig/kernel/sched/fair.c 2014-08-07 09:36:05.954916998 -0500
+++ linux/kernel/sched/fair.c 2014-08-07 09:36:05.906917903 -0500
@@ -6490,7 +6490,7 @@
struct sched_group *group;
struct rq *busiest;
unsigned long flags;
- struct cpumask *cpus = __get_cpu_var(load_balance_mask);
+ struct cpumask *cpus = this_cpu_cpumask_var_t_ptr(load_balance_mask);
struct lb_env env = {
.sd = sd,
Index: linux/kernel/sched/rt.c
===================================================================
--- linux.orig/kernel/sched/rt.c 2014-08-07 09:36:05.954916998 -0500
+++ linux/kernel/sched/rt.c 2014-08-07 09:36:05.906917903 -0500
@@ -1522,7 +1522,7 @@
static int find_lowest_rq(struct task_struct *task)
{
struct sched_domain *sd;
- struct cpumask *lowest_mask = __get_cpu_var(local_cpu_mask);
+ struct cpumask *lowest_mask = this_cpu_cpumask_var_t_ptr(local_cpu_mask);
int this_cpu = smp_processor_id();
int cpu = task_cpu(task);
Index: linux/arch/x86/include/asm/perf_event_p4.h
===================================================================
--- linux.orig/arch/x86/include/asm/perf_event_p4.h 2014-08-07 09:36:05.954916998 -0500
+++ linux/arch/x86/include/asm/perf_event_p4.h 2014-08-07 09:36:05.910917828 -0500
@@ -189,7 +189,7 @@
{
#ifdef CONFIG_SMP
if (smp_num_siblings == 2)
- return cpu != cpumask_first(__get_cpu_var(cpu_sibling_map));
+ return cpu != cpumask_first(this_cpu_cpumask_var_t_ptr(cpu_sibling_map));
#endif
return 0;
}
Index: linux/arch/x86/oprofile/op_model_p4.c
===================================================================
--- linux.orig/arch/x86/oprofile/op_model_p4.c 2014-08-07 09:36:05.954916998 -0500
+++ linux/arch/x86/oprofile/op_model_p4.c 2014-08-07 09:36:05.910917828 -0500
@@ -372,7 +372,7 @@
{
#ifdef CONFIG_SMP
int cpu = smp_processor_id();
- return cpu != cpumask_first(__get_cpu_var(cpu_sibling_map));
+ return cpu != cpumask_first(this_cpu_cpumask_var_t_ptr(cpu_sibling_map));
#endif
return 0;
}
--
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