linux/kernel/delayacct.c
Sebastian Andrzej Siewior 02acc80d19 delayacct: Use raw_spinlocks
try_to_wake_up() might invoke delayacct_blkio_end() while holding the
pi_lock (which is a raw_spinlock_t). delayacct_blkio_end() acquires
task_delay_info.lock which is a spinlock_t. This causes a might sleep splat
on -RT where non raw spinlocks are converted to 'sleeping' spinlocks.

task_delay_info.lock is only held for a short amount of time so it's not a
problem latency wise to make convert it to a raw spinlock.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Balbir Singh <bsingharora@gmail.com>
Link: https://lkml.kernel.org/r/20180423161024.6710-1-bigeasy@linutronix.de
2018-04-27 14:34:51 +02:00

172 lines
4.7 KiB
C

/* delayacct.c - per-task delay accounting
*
* Copyright (C) Shailabh Nagar, IBM Corp. 2006
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it would be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
* the GNU General Public License for more details.
*/
#include <linux/sched.h>
#include <linux/sched/task.h>
#include <linux/sched/cputime.h>
#include <linux/slab.h>
#include <linux/taskstats.h>
#include <linux/time.h>
#include <linux/sysctl.h>
#include <linux/delayacct.h>
#include <linux/module.h>
int delayacct_on __read_mostly = 1; /* Delay accounting turned on/off */
EXPORT_SYMBOL_GPL(delayacct_on);
struct kmem_cache *delayacct_cache;
static int __init delayacct_setup_disable(char *str)
{
delayacct_on = 0;
return 1;
}
__setup("nodelayacct", delayacct_setup_disable);
void delayacct_init(void)
{
delayacct_cache = KMEM_CACHE(task_delay_info, SLAB_PANIC|SLAB_ACCOUNT);
delayacct_tsk_init(&init_task);
}
void __delayacct_tsk_init(struct task_struct *tsk)
{
tsk->delays = kmem_cache_zalloc(delayacct_cache, GFP_KERNEL);
if (tsk->delays)
raw_spin_lock_init(&tsk->delays->lock);
}
/*
* Finish delay accounting for a statistic using its timestamps (@start),
* accumalator (@total) and @count
*/
static void delayacct_end(raw_spinlock_t *lock, u64 *start, u64 *total,
u32 *count)
{
s64 ns = ktime_get_ns() - *start;
unsigned long flags;
if (ns > 0) {
raw_spin_lock_irqsave(lock, flags);
*total += ns;
(*count)++;
raw_spin_unlock_irqrestore(lock, flags);
}
}
void __delayacct_blkio_start(void)
{
current->delays->blkio_start = ktime_get_ns();
}
/*
* We cannot rely on the `current` macro, as we haven't yet switched back to
* the process being woken.
*/
void __delayacct_blkio_end(struct task_struct *p)
{
struct task_delay_info *delays = p->delays;
u64 *total;
u32 *count;
if (p->delays->flags & DELAYACCT_PF_SWAPIN) {
total = &delays->swapin_delay;
count = &delays->swapin_count;
} else {
total = &delays->blkio_delay;
count = &delays->blkio_count;
}
delayacct_end(&delays->lock, &delays->blkio_start, total, count);
}
int __delayacct_add_tsk(struct taskstats *d, struct task_struct *tsk)
{
u64 utime, stime, stimescaled, utimescaled;
unsigned long long t2, t3;
unsigned long flags, t1;
s64 tmp;
task_cputime(tsk, &utime, &stime);
tmp = (s64)d->cpu_run_real_total;
tmp += utime + stime;
d->cpu_run_real_total = (tmp < (s64)d->cpu_run_real_total) ? 0 : tmp;
task_cputime_scaled(tsk, &utimescaled, &stimescaled);
tmp = (s64)d->cpu_scaled_run_real_total;
tmp += utimescaled + stimescaled;
d->cpu_scaled_run_real_total =
(tmp < (s64)d->cpu_scaled_run_real_total) ? 0 : tmp;
/*
* No locking available for sched_info (and too expensive to add one)
* Mitigate by taking snapshot of values
*/
t1 = tsk->sched_info.pcount;
t2 = tsk->sched_info.run_delay;
t3 = tsk->se.sum_exec_runtime;
d->cpu_count += t1;
tmp = (s64)d->cpu_delay_total + t2;
d->cpu_delay_total = (tmp < (s64)d->cpu_delay_total) ? 0 : tmp;
tmp = (s64)d->cpu_run_virtual_total + t3;
d->cpu_run_virtual_total =
(tmp < (s64)d->cpu_run_virtual_total) ? 0 : tmp;
/* zero XXX_total, non-zero XXX_count implies XXX stat overflowed */
raw_spin_lock_irqsave(&tsk->delays->lock, flags);
tmp = d->blkio_delay_total + tsk->delays->blkio_delay;
d->blkio_delay_total = (tmp < d->blkio_delay_total) ? 0 : tmp;
tmp = d->swapin_delay_total + tsk->delays->swapin_delay;
d->swapin_delay_total = (tmp < d->swapin_delay_total) ? 0 : tmp;
tmp = d->freepages_delay_total + tsk->delays->freepages_delay;
d->freepages_delay_total = (tmp < d->freepages_delay_total) ? 0 : tmp;
d->blkio_count += tsk->delays->blkio_count;
d->swapin_count += tsk->delays->swapin_count;
d->freepages_count += tsk->delays->freepages_count;
raw_spin_unlock_irqrestore(&tsk->delays->lock, flags);
return 0;
}
__u64 __delayacct_blkio_ticks(struct task_struct *tsk)
{
__u64 ret;
unsigned long flags;
raw_spin_lock_irqsave(&tsk->delays->lock, flags);
ret = nsec_to_clock_t(tsk->delays->blkio_delay +
tsk->delays->swapin_delay);
raw_spin_unlock_irqrestore(&tsk->delays->lock, flags);
return ret;
}
void __delayacct_freepages_start(void)
{
current->delays->freepages_start = ktime_get_ns();
}
void __delayacct_freepages_end(void)
{
delayacct_end(
&current->delays->lock,
&current->delays->freepages_start,
&current->delays->freepages_delay,
&current->delays->freepages_count);
}