linux/kernel/delayacct.c
Peter Zijlstra 64efade11c [PATCH] lockdep: fix delayacct locking bug
Make the delayacct lock irqsave; this avoids the possible deadlock where
an interrupt is taken while holding the delayacct lock which needs to
take the delayacct lock.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Shailabh Nagar <nagar@watson.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-11-06 01:46:23 -08:00

166 lines
4.3 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/slab.h>
#include <linux/time.h>
#include <linux/sysctl.h>
#include <linux/delayacct.h>
int delayacct_on __read_mostly = 1; /* Delay accounting turned on/off */
kmem_cache_t *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_create("delayacct_cache",
sizeof(struct task_delay_info),
0,
SLAB_PANIC,
NULL, NULL);
delayacct_tsk_init(&init_task);
}
void __delayacct_tsk_init(struct task_struct *tsk)
{
tsk->delays = kmem_cache_zalloc(delayacct_cache, SLAB_KERNEL);
if (tsk->delays)
spin_lock_init(&tsk->delays->lock);
}
/*
* Start accounting for a delay statistic using
* its starting timestamp (@start)
*/
static inline void delayacct_start(struct timespec *start)
{
do_posix_clock_monotonic_gettime(start);
}
/*
* Finish delay accounting for a statistic using
* its timestamps (@start, @end), accumalator (@total) and @count
*/
static void delayacct_end(struct timespec *start, struct timespec *end,
u64 *total, u32 *count)
{
struct timespec ts;
s64 ns;
unsigned long flags;
do_posix_clock_monotonic_gettime(end);
ts = timespec_sub(*end, *start);
ns = timespec_to_ns(&ts);
if (ns < 0)
return;
spin_lock_irqsave(&current->delays->lock, flags);
*total += ns;
(*count)++;
spin_unlock_irqrestore(&current->delays->lock, flags);
}
void __delayacct_blkio_start(void)
{
delayacct_start(&current->delays->blkio_start);
}
void __delayacct_blkio_end(void)
{
if (current->delays->flags & DELAYACCT_PF_SWAPIN)
/* Swapin block I/O */
delayacct_end(&current->delays->blkio_start,
&current->delays->blkio_end,
&current->delays->swapin_delay,
&current->delays->swapin_count);
else /* Other block I/O */
delayacct_end(&current->delays->blkio_start,
&current->delays->blkio_end,
&current->delays->blkio_delay,
&current->delays->blkio_count);
}
int __delayacct_add_tsk(struct taskstats *d, struct task_struct *tsk)
{
s64 tmp;
struct timespec ts;
unsigned long t1,t2,t3;
unsigned long flags;
/* Though tsk->delays accessed later, early exit avoids
* unnecessary returning of other data
*/
if (!tsk->delays)
goto done;
tmp = (s64)d->cpu_run_real_total;
cputime_to_timespec(tsk->utime + tsk->stime, &ts);
tmp += timespec_to_ns(&ts);
d->cpu_run_real_total = (tmp < (s64)d->cpu_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.pcnt;
t2 = tsk->sched_info.run_delay;
t3 = tsk->sched_info.cpu_time;
d->cpu_count += t1;
jiffies_to_timespec(t2, &ts);
tmp = (s64)d->cpu_delay_total + timespec_to_ns(&ts);
d->cpu_delay_total = (tmp < (s64)d->cpu_delay_total) ? 0 : tmp;
tmp = (s64)d->cpu_run_virtual_total + (s64)jiffies_to_usecs(t3) * 1000;
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 */
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;
d->blkio_count += tsk->delays->blkio_count;
d->swapin_count += tsk->delays->swapin_count;
spin_unlock_irqrestore(&tsk->delays->lock, flags);
done:
return 0;
}
__u64 __delayacct_blkio_ticks(struct task_struct *tsk)
{
__u64 ret;
unsigned long flags;
spin_lock_irqsave(&tsk->delays->lock, flags);
ret = nsec_to_clock_t(tsk->delays->blkio_delay +
tsk->delays->swapin_delay);
spin_unlock_irqrestore(&tsk->delays->lock, flags);
return ret;
}