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35df17c57c
Cleanup allocation and freeing of tsk->delays used by delay accounting. This solves two problems reported for delay accounting: 1. oops in __delayacct_blkio_ticks http://www.uwsg.indiana.edu/hypermail/linux/kernel/0608.2/1844.html Currently tsk->delays is getting freed too early in task exit which can cause a NULL tsk->delays to get accessed via reading of /proc/<tgid>/stats. The patch fixes this problem by freeing tsk->delays closer to when task_struct itself is freed up. As a result, it also eliminates the use of tsk->delays_lock which was only being used (inadequately) to safeguard access to tsk->delays while a task was exiting. 2. Possible memory leak in kernel/delayacct.c http://www.uwsg.indiana.edu/hypermail/linux/kernel/0608.2/1389.html The patch cleans up tsk->delays allocations after a bad fork which was missing earlier. The patch has been tested to fix the problems listed above and stress tested with rapid calls to delay accounting's taskstats command interface (which is the other path that can access the same data, besides the /proc interface causing the oops above). Signed-off-by: Shailabh Nagar <nagar@watson.ibm.com> Cc: Balbir Singh <balbir@in.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
122 lines
3.2 KiB
C
122 lines
3.2 KiB
C
/* delayacct.h - per-task delay accounting
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*
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* Copyright (C) Shailabh Nagar, IBM Corp. 2006
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
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* the GNU General Public License for more details.
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*
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*/
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#ifndef _LINUX_DELAYACCT_H
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#define _LINUX_DELAYACCT_H
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#include <linux/sched.h>
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#include <linux/taskstats_kern.h>
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/*
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* Per-task flags relevant to delay accounting
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* maintained privately to avoid exhausting similar flags in sched.h:PF_*
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* Used to set current->delays->flags
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*/
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#define DELAYACCT_PF_SWAPIN 0x00000001 /* I am doing a swapin */
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#ifdef CONFIG_TASK_DELAY_ACCT
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extern int delayacct_on; /* Delay accounting turned on/off */
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extern kmem_cache_t *delayacct_cache;
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extern void delayacct_init(void);
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extern void __delayacct_tsk_init(struct task_struct *);
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extern void __delayacct_tsk_exit(struct task_struct *);
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extern void __delayacct_blkio_start(void);
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extern void __delayacct_blkio_end(void);
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extern int __delayacct_add_tsk(struct taskstats *, struct task_struct *);
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extern __u64 __delayacct_blkio_ticks(struct task_struct *);
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static inline void delayacct_set_flag(int flag)
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{
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if (current->delays)
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current->delays->flags |= flag;
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}
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static inline void delayacct_clear_flag(int flag)
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{
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if (current->delays)
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current->delays->flags &= ~flag;
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}
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static inline void delayacct_tsk_init(struct task_struct *tsk)
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{
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/* reinitialize in case parent's non-null pointer was dup'ed*/
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tsk->delays = NULL;
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if (delayacct_on)
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__delayacct_tsk_init(tsk);
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}
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/* Free tsk->delays. Called from bad fork and __put_task_struct
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* where there's no risk of tsk->delays being accessed elsewhere
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*/
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static inline void delayacct_tsk_free(struct task_struct *tsk)
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{
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if (tsk->delays)
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kmem_cache_free(delayacct_cache, tsk->delays);
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tsk->delays = NULL;
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}
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static inline void delayacct_blkio_start(void)
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{
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if (current->delays)
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__delayacct_blkio_start();
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}
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static inline void delayacct_blkio_end(void)
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{
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if (current->delays)
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__delayacct_blkio_end();
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}
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static inline int delayacct_add_tsk(struct taskstats *d,
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struct task_struct *tsk)
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{
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if (!delayacct_on || !tsk->delays)
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return 0;
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return __delayacct_add_tsk(d, tsk);
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}
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static inline __u64 delayacct_blkio_ticks(struct task_struct *tsk)
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{
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if (tsk->delays)
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return __delayacct_blkio_ticks(tsk);
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return 0;
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}
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#else
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static inline void delayacct_set_flag(int flag)
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{}
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static inline void delayacct_clear_flag(int flag)
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{}
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static inline void delayacct_init(void)
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{}
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static inline void delayacct_tsk_init(struct task_struct *tsk)
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{}
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static inline void delayacct_tsk_free(struct task_struct *tsk)
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{}
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static inline void delayacct_blkio_start(void)
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{}
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static inline void delayacct_blkio_end(void)
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{}
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static inline int delayacct_add_tsk(struct taskstats *d,
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struct task_struct *tsk)
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{ return 0; }
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static inline __u64 delayacct_blkio_ticks(struct task_struct *tsk)
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{ return 0; }
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#endif /* CONFIG_TASK_DELAY_ACCT */
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#endif
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