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linux/drivers/isdn/divert/divert_procfs.c
Arnd Bergmann c11da83bda isdn: divert, hysdn: fix interruptible_sleep_on race 
These two drivers use identical code for their procfs status
file handling, which contains a small race against status
data becoming available while reading the file.

This uses wait_event_interruptible instead to fix this
particular race and eventually get rid of all sleep_on
instances. There seems to be another race involving
multiple concurrent readers of the same procfs file, which
I don't try to fix here.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Karsten Keil <isdn@linux-pingi.de>
Cc: netdev@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>
2014-02-26 16:06:13 -05:00

337 lines
8.8 KiB
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/* $Id: divert_procfs.c,v 1.11.6.2 2001/09/23 22:24:36 kai Exp $
*
* Filesystem handling for the diversion supplementary services.
*
* Copyright 1998 by Werner Cornelius (werner@isdn4linux.de)
*
* This software may be used and distributed according to the terms
* of the GNU General Public License, incorporated herein by reference.
*
*/
#include <linux/module.h>
#include <linux/poll.h>
#include <linux/slab.h>
#ifdef CONFIG_PROC_FS
#include <linux/proc_fs.h>
#else
#include <linux/fs.h>
#endif
#include <linux/sched.h>
#include <linux/isdnif.h>
#include <net/net_namespace.h>
#include <linux/mutex.h>
#include "isdn_divert.h"
/*********************************/
/* Variables for interface queue */
/*********************************/
ulong if_used = 0; /* number of interface users */
static DEFINE_MUTEX(isdn_divert_mutex);
static struct divert_info *divert_info_head = NULL; /* head of queue */
static struct divert_info *divert_info_tail = NULL; /* pointer to last entry */
static DEFINE_SPINLOCK(divert_info_lock);/* lock for queue */
static wait_queue_head_t rd_queue;
/*********************************/
/* put an info buffer into queue */
/*********************************/
void
put_info_buffer(char *cp)
{
struct divert_info *ib;
unsigned long flags;
if (if_used <= 0)
return;
if (!cp)
return;
if (!*cp)
return;
if (!(ib = kmalloc(sizeof(struct divert_info) + strlen(cp), GFP_ATOMIC)))
return; /* no memory */
strcpy(ib->info_start, cp); /* set output string */
ib->next = NULL;
spin_lock_irqsave(&divert_info_lock, flags);
ib->usage_cnt = if_used;
if (!divert_info_head)
divert_info_head = ib; /* new head */
else
divert_info_tail->next = ib; /* follows existing messages */
divert_info_tail = ib; /* new tail */
/* delete old entrys */
while (divert_info_head->next) {
if ((divert_info_head->usage_cnt <= 0) &&
(divert_info_head->next->usage_cnt <= 0)) {
ib = divert_info_head;
divert_info_head = divert_info_head->next;
kfree(ib);
} else
break;
} /* divert_info_head->next */
spin_unlock_irqrestore(&divert_info_lock, flags);
wake_up_interruptible(&(rd_queue));
} /* put_info_buffer */
#ifdef CONFIG_PROC_FS
/**********************************/
/* deflection device read routine */
/**********************************/
static ssize_t
isdn_divert_read(struct file *file, char __user *buf, size_t count, loff_t *off)
{
struct divert_info *inf;
int len;
if (!(inf = *((struct divert_info **) file->private_data))) {
if (file->f_flags & O_NONBLOCK)
return -EAGAIN;
wait_event_interruptible(rd_queue, (inf =
*((struct divert_info **) file->private_data)));
}
if (!inf)
return (0);
inf->usage_cnt--; /* new usage count */
file->private_data = &inf->next; /* next structure */
if ((len = strlen(inf->info_start)) <= count) {
if (copy_to_user(buf, inf->info_start, len))
return -EFAULT;
*off += len;
return (len);
}
return (0);
} /* isdn_divert_read */
/**********************************/
/* deflection device write routine */
/**********************************/
static ssize_t
isdn_divert_write(struct file *file, const char __user *buf, size_t count, loff_t *off)
{
return (-ENODEV);
} /* isdn_divert_write */
/***************************************/
/* select routines for various kernels */
/***************************************/
static unsigned int
isdn_divert_poll(struct file *file, poll_table *wait)
{
unsigned int mask = 0;
poll_wait(file, &(rd_queue), wait);
/* mask = POLLOUT | POLLWRNORM; */
if (*((struct divert_info **) file->private_data)) {
mask |= POLLIN | POLLRDNORM;
}
return mask;
} /* isdn_divert_poll */
/****************/
/* Open routine */
/****************/
static int
isdn_divert_open(struct inode *ino, struct file *filep)
{
unsigned long flags;
spin_lock_irqsave(&divert_info_lock, flags);
if_used++;
if (divert_info_head)
filep->private_data = &(divert_info_tail->next);
else
filep->private_data = &divert_info_head;
spin_unlock_irqrestore(&divert_info_lock, flags);
/* start_divert(); */
return nonseekable_open(ino, filep);
} /* isdn_divert_open */
/*******************/
/* close routine */
/*******************/
static int
isdn_divert_close(struct inode *ino, struct file *filep)
{
struct divert_info *inf;
unsigned long flags;
spin_lock_irqsave(&divert_info_lock, flags);
if_used--;
inf = *((struct divert_info **) filep->private_data);
while (inf) {
inf->usage_cnt--;
inf = inf->next;
}
if (if_used <= 0)
while (divert_info_head) {
inf = divert_info_head;
divert_info_head = divert_info_head->next;
kfree(inf);
}
spin_unlock_irqrestore(&divert_info_lock, flags);
return (0);
} /* isdn_divert_close */
/*********/
/* IOCTL */
/*********/
static int isdn_divert_ioctl_unlocked(struct file *file, uint cmd, ulong arg)
{
divert_ioctl dioctl;
int i;
unsigned long flags;
divert_rule *rulep;
char *cp;
if (copy_from_user(&dioctl, (void __user *) arg, sizeof(dioctl)))
return -EFAULT;
switch (cmd) {
case IIOCGETVER:
dioctl.drv_version = DIVERT_IIOC_VERSION; /* set version */
break;
case IIOCGETDRV:
if ((dioctl.getid.drvid = divert_if.name_to_drv(dioctl.getid.drvnam)) < 0)
return (-EINVAL);
break;
case IIOCGETNAM:
cp = divert_if.drv_to_name(dioctl.getid.drvid);
if (!cp)
return (-EINVAL);
if (!*cp)
return (-EINVAL);
strcpy(dioctl.getid.drvnam, cp);
break;
case IIOCGETRULE:
if (!(rulep = getruleptr(dioctl.getsetrule.ruleidx)))
return (-EINVAL);
dioctl.getsetrule.rule = *rulep; /* copy data */
break;
case IIOCMODRULE:
if (!(rulep = getruleptr(dioctl.getsetrule.ruleidx)))
return (-EINVAL);
spin_lock_irqsave(&divert_lock, flags);
*rulep = dioctl.getsetrule.rule; /* copy data */
spin_unlock_irqrestore(&divert_lock, flags);
return (0); /* no copy required */
break;
case IIOCINSRULE:
return (insertrule(dioctl.getsetrule.ruleidx, &dioctl.getsetrule.rule));
break;
case IIOCDELRULE:
return (deleterule(dioctl.getsetrule.ruleidx));
break;
case IIOCDODFACT:
return (deflect_extern_action(dioctl.fwd_ctrl.subcmd,
dioctl.fwd_ctrl.callid,
dioctl.fwd_ctrl.to_nr));
case IIOCDOCFACT:
case IIOCDOCFDIS:
case IIOCDOCFINT:
if (!divert_if.drv_to_name(dioctl.cf_ctrl.drvid))
return (-EINVAL); /* invalid driver */
if (strnlen(dioctl.cf_ctrl.msn, sizeof(dioctl.cf_ctrl.msn)) ==
sizeof(dioctl.cf_ctrl.msn))
return -EINVAL;
if (strnlen(dioctl.cf_ctrl.fwd_nr, sizeof(dioctl.cf_ctrl.fwd_nr)) ==
sizeof(dioctl.cf_ctrl.fwd_nr))
return -EINVAL;
if ((i = cf_command(dioctl.cf_ctrl.drvid,
(cmd == IIOCDOCFACT) ? 1 : (cmd == IIOCDOCFDIS) ? 0 : 2,
dioctl.cf_ctrl.cfproc,
dioctl.cf_ctrl.msn,
dioctl.cf_ctrl.service,
dioctl.cf_ctrl.fwd_nr,
&dioctl.cf_ctrl.procid)))
return (i);
break;
default:
return (-EINVAL);
} /* switch cmd */
return copy_to_user((void __user *)arg, &dioctl, sizeof(dioctl)) ? -EFAULT : 0;
} /* isdn_divert_ioctl */
static long isdn_divert_ioctl(struct file *file, uint cmd, ulong arg)
{
long ret;
mutex_lock(&isdn_divert_mutex);
ret = isdn_divert_ioctl_unlocked(file, cmd, arg);
mutex_unlock(&isdn_divert_mutex);
return ret;
}
static const struct file_operations isdn_fops =
{
.owner = THIS_MODULE,
.llseek = no_llseek,
.read = isdn_divert_read,
.write = isdn_divert_write,
.poll = isdn_divert_poll,
.unlocked_ioctl = isdn_divert_ioctl,
.open = isdn_divert_open,
.release = isdn_divert_close,
};
/****************************/
/* isdn subdir in /proc/net */
/****************************/
static struct proc_dir_entry *isdn_proc_entry = NULL;
static struct proc_dir_entry *isdn_divert_entry = NULL;
#endif /* CONFIG_PROC_FS */
/***************************************************************************/
/* divert_dev_init must be called before the proc filesystem may be used */
/***************************************************************************/
int
divert_dev_init(void)
{
init_waitqueue_head(&rd_queue);
#ifdef CONFIG_PROC_FS
isdn_proc_entry = proc_mkdir("isdn", init_net.proc_net);
if (!isdn_proc_entry)
return (-1);
isdn_divert_entry = proc_create("divert", S_IFREG | S_IRUGO,
isdn_proc_entry, &isdn_fops);
if (!isdn_divert_entry) {
remove_proc_entry("isdn", init_net.proc_net);
return (-1);
}
#endif /* CONFIG_PROC_FS */
return (0);
} /* divert_dev_init */
/***************************************************************************/
/* divert_dev_deinit must be called before leaving isdn when included as */
/* a module. */
/***************************************************************************/
int
divert_dev_deinit(void)
{
#ifdef CONFIG_PROC_FS
remove_proc_entry("divert", isdn_proc_entry);
remove_proc_entry("isdn", init_net.proc_net);
#endif /* CONFIG_PROC_FS */
return (0);
} /* divert_dev_deinit */
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