Fix
BUG: using smp_processor_id() in preemptible [00000000] code: s2disk/3392
caller is nr_iowait_cpu+0xe/0x1e
Pid: 3392, comm: s2disk Not tainted 2.6.35-rc3-dbg-00106-ga75e02b #2
Call Trace:
[<c1184c55>] debug_smp_processor_id+0xa5/0xbc
[<c10282a5>] nr_iowait_cpu+0xe/0x1e
[<c104ab7c>] update_ts_time_stats+0x32/0x6c
[<c104ac73>] get_cpu_idle_time_us+0x36/0x58
[<c124229b>] get_cpu_idle_time+0x12/0x74
[<c1242963>] cpufreq_governor_dbs+0xc3/0x2dc
[<c1240437>] __cpufreq_governor+0x51/0x85
[<c1241190>] __cpufreq_set_policy+0x10c/0x13d
[<c12413d3>] cpufreq_add_dev_interface+0x212/0x233
[<c1241b1e>] ? handle_update+0x0/0xd
[<c1241a18>] cpufreq_add_dev+0x34b/0x35a
[<c103c973>] ? schedule_delayed_work_on+0x11/0x13
[<c12c14db>] cpufreq_cpu_callback+0x59/0x63
[<c1042f39>] notifier_call_chain+0x26/0x48
[<c1042f7d>] __raw_notifier_call_chain+0xe/0x10
[<c102efb9>] __cpu_notify+0x15/0x29
[<c102efda>] cpu_notify+0xd/0xf
[<c12bfb30>] _cpu_up+0xaf/0xd2
[<c12b3ad4>] enable_nonboot_cpus+0x3d/0x94
[<c1055eef>] hibernation_snapshot+0x104/0x1a2
[<c1058b49>] snapshot_ioctl+0x24b/0x53e
[<c1028ad1>] ? sub_preempt_count+0x7c/0x89
[<c10ab91d>] vfs_ioctl+0x2e/0x8c
[<c10588fe>] ? snapshot_ioctl+0x0/0x53e
[<c10ac2c7>] do_vfs_ioctl+0x42f/0x45a
[<c10a0ba5>] ? fsnotify_modify+0x4f/0x5a
[<c11e9dc3>] ? tty_write+0x0/0x1d0
[<c10a12d6>] ? vfs_write+0xa2/0xda
[<c10ac333>] sys_ioctl+0x41/0x62
[<c10027d3>] sysenter_do_call+0x12/0x2d
The initial fix was to use get_cpu/put_cpu in nr_iowait_cpu. However,
Arjan stated that "the bug is that it needs to be nr_iowait_cpu(int cpu)".
This patch introduces nr_iowait_cpu(int cpu) and changes to its callers.
Arjan also pointed out that we can't use get_cpu/put_cpu in update_ts_time_stats
since we "pick the current cpu, rather than the one denoted by ts" in that case.
To match given *ts and cpu denoted by *ts we use new field in the struct tick_sched: int cpu.
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
---
diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
index 52ff8aa..4871ed5 100644
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -137,14 +137,17 @@ static inline int which_bucket(unsigned int duration)
{
int bucket = 0;
+ int cpu = get_cpu();
/*
* We keep two groups of stats; one with no
* IO pending, one without.
* This allows us to calculate
* E(duration)|iowait
*/
- if (nr_iowait_cpu())
+ if (nr_iowait_cpu(cpu))
bucket = BUCKETS/2;
+
+ put_cpu();
if (duration < 10)
return bucket;
@@ -169,14 +172,17 @@ static inline int which_bucket(unsigned int duration)
static inline int performance_multiplier(void)
{
int mult = 1;
-
+ int cpu = get_cpu();
+
/* for higher loadavg, we are more reluctant */
mult += 2 * get_loadavg();
/* for IO wait tasks (per cpu!) we add 5x each */
- mult += 10 * nr_iowait_cpu();
+ mult += 10 * nr_iowait_cpu(cpu);
+ put_cpu();
+
return mult;
}
diff --git a/include/linux/sched.h b/include/linux/sched.h
index f118809..747fcae 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -139,7 +139,7 @@ extern int nr_processes(void);
extern unsigned long nr_running(void);
extern unsigned long nr_uninterruptible(void);
extern unsigned long nr_iowait(void);
-extern unsigned long nr_iowait_cpu(void);
+extern unsigned long nr_iowait_cpu(int cpu);
extern unsigned long this_cpu_load(void);
diff --git a/include/linux/tick.h b/include/linux/tick.h
index b232ccc..db14691 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -51,6 +51,7 @@ struct tick_sched {
unsigned long check_clocks;
enum tick_nohz_mode nohz_mode;
ktime_t idle_tick;
+ int cpu;
int inidle;
int tick_stopped;
unsigned long idle_jiffies;
diff --git a/kernel/sched.c b/kernel/sched.c
index f8b8996..f61b48e 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2864,9 +2864,9 @@ unsigned long nr_iowait(void)
return sum;
}
-unsigned long nr_iowait_cpu(void)
+unsigned long nr_iowait_cpu(int cpu)
{
- struct rq *this = this_rq();
+ struct rq *this = cpu_rq(cpu);
return atomic_read(&this->nr_iowait);
}
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 1d7b9bc..1907037 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -38,6 +38,9 @@ static ktime_t last_jiffies_update;
struct tick_sched *tick_get_tick_sched(int cpu)
{
+ /*FIXME: Arjan van de Ven:
+ can we do this bit once, when the ts structure gets initialized?*/
+ per_cpu(tick_cpu_sched, cpu).cpu = cpu;
return &per_cpu(tick_cpu_sched, cpu);
}
@@ -137,7 +140,7 @@ __setup("nohz=", setup_tick_nohz);
static void tick_nohz_update_jiffies(ktime_t now)
{
int cpu = smp_processor_id();
- struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
+ struct tick_sched *ts = tick_get_tick_sched(cpu);
unsigned long flags;
cpumask_clear_cpu(cpu, nohz_cpu_mask);
@@ -161,7 +164,7 @@ update_ts_time_stats(struct tick_sched *ts, ktime_t now, u64 *last_update_time)
if (ts->idle_active) {
delta = ktime_sub(now, ts->idle_entrytime);
ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);
- if (nr_iowait_cpu() > 0)
+ if (nr_iowait_cpu(ts->cpu) > 0)
ts->iowait_sleeptime = ktime_add(ts->iowait_sleeptime, delta);
ts->idle_entrytime = now;
}
@@ -173,7 +176,7 @@ update_ts_time_stats(struct tick_sched *ts, ktime_t now, u64 *last_update_time)
static void tick_nohz_stop_idle(int cpu, ktime_t now)
{
- struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
+ struct tick_sched *ts = tick_get_tick_sched(cpu);
update_ts_time_stats(ts, now, NULL);
ts->idle_active = 0;
@@ -211,7 +214,7 @@ static ktime_t tick_nohz_start_idle(struct tick_sched *ts)
*/
u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time)
{
- struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
+ struct tick_sched *ts = tick_get_tick_sched(cpu);
if (!tick_nohz_enabled)
return -1;
@@ -237,7 +240,7 @@ EXPORT_SYMBOL_GPL(get_cpu_idle_time_us);
*/
u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time)
{
- struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
+ struct tick_sched *ts = tick_get_tick_sched(cpu);
if (!tick_nohz_enabled)
return -1;
@@ -267,7 +270,7 @@ void tick_nohz_stop_sched_tick(int inidle)
local_irq_save(flags);
cpu = smp_processor_id();
- ts = &per_cpu(tick_cpu_sched, cpu);
+ ts = tick_get_tick_sched(cpu);
/*
* Call to tick_nohz_start_idle stops the last_update_time from being
@@ -508,7 +511,7 @@ static void tick_nohz_restart(struct tick_sched *ts, ktime_t now)
void tick_nohz_restart_sched_tick(void)
{
int cpu = smp_processor_id();
- struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
+ struct tick_sched *ts = tick_get_tick_sched(cpu);
#ifndef CONFIG_VIRT_CPU_ACCOUNTING
unsigned long ticks;
#endif
@@ -671,7 +674,7 @@ static void tick_nohz_kick_tick(int cpu, ktime_t now)
#if 0
/* Switch back to 2.6.27 behaviour */
- struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
+ struct tick_sched *ts = tick_get_tick_sched(cpu);
ktime_t delta;
/*
@@ -688,7 +691,7 @@ static void tick_nohz_kick_tick(int cpu, ktime_t now)
static inline void tick_check_nohz(int cpu)
{
- struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
+ struct tick_sched *ts = tick_get_tick_sched(cpu);
ktime_t now;
if (!ts->idle_active && !ts->tick_stopped)
@@ -818,7 +821,7 @@ void tick_setup_sched_timer(void)
#if defined CONFIG_NO_HZ || defined CONFIG_HIGH_RES_TIMERS
void tick_cancel_sched_timer(int cpu)
{
- struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
+ struct tick_sched *ts = tick_get_tick_sched(cpu);
# ifdef CONFIG_HIGH_RES_TIMERS
if (ts->sched_timer.base)
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