[PATCH] avoid using smp_processor_id() in preemptible code (nr_iowait_cpu)

Sergey Senozhatsky
2010-06-15T06:19:27Z

Fixing
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

Initially fix was to use get_cpu/put_cpu in nr_iowait_cpu. However,
Arjan van de Ven 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 it callers.

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>

---

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/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..101e8aa 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -159,10 +159,12 @@ update_ts_time_stats(struct tick_sched *ts, ktime_t now, u64 *last_update_time)
ktime_t delta;

if (ts->idle_active) {
+ int cpu = get_cpu();
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(cpu) > 0)
ts->iowait_sleeptime = ktime_add(ts->iowait_sleeptime, delta);
+ put_cpu();
ts->idle_entrytime = now;
}