mirror of
https://github.com/torvalds/linux.git
synced 2024-12-05 18:41:23 +00:00
d48eb23315
The eventfd was using the unlocked waitqueue operations, but it was using a different lock, so poll_wait() would race with it. This makes eventfd directly use the waitqueue lock. Signed-off-by: Davide Libenzi <davidel@xmailserver.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
227 lines
5.1 KiB
C
227 lines
5.1 KiB
C
/*
|
|
* fs/eventfd.c
|
|
*
|
|
* Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org>
|
|
*
|
|
*/
|
|
|
|
#include <linux/file.h>
|
|
#include <linux/poll.h>
|
|
#include <linux/init.h>
|
|
#include <linux/fs.h>
|
|
#include <linux/sched.h>
|
|
#include <linux/kernel.h>
|
|
#include <linux/list.h>
|
|
#include <linux/spinlock.h>
|
|
#include <linux/anon_inodes.h>
|
|
#include <linux/eventfd.h>
|
|
|
|
struct eventfd_ctx {
|
|
wait_queue_head_t wqh;
|
|
/*
|
|
* Every time that a write(2) is performed on an eventfd, the
|
|
* value of the __u64 being written is added to "count" and a
|
|
* wakeup is performed on "wqh". A read(2) will return the "count"
|
|
* value to userspace, and will reset "count" to zero. The kernel
|
|
* size eventfd_signal() also, adds to the "count" counter and
|
|
* issue a wakeup.
|
|
*/
|
|
__u64 count;
|
|
};
|
|
|
|
/*
|
|
* Adds "n" to the eventfd counter "count". Returns "n" in case of
|
|
* success, or a value lower then "n" in case of coutner overflow.
|
|
* This function is supposed to be called by the kernel in paths
|
|
* that do not allow sleeping. In this function we allow the counter
|
|
* to reach the ULLONG_MAX value, and we signal this as overflow
|
|
* condition by returining a POLLERR to poll(2).
|
|
*/
|
|
int eventfd_signal(struct file *file, int n)
|
|
{
|
|
struct eventfd_ctx *ctx = file->private_data;
|
|
unsigned long flags;
|
|
|
|
if (n < 0)
|
|
return -EINVAL;
|
|
spin_lock_irqsave(&ctx->wqh.lock, flags);
|
|
if (ULLONG_MAX - ctx->count < n)
|
|
n = (int) (ULLONG_MAX - ctx->count);
|
|
ctx->count += n;
|
|
if (waitqueue_active(&ctx->wqh))
|
|
wake_up_locked(&ctx->wqh);
|
|
spin_unlock_irqrestore(&ctx->wqh.lock, flags);
|
|
|
|
return n;
|
|
}
|
|
|
|
static int eventfd_release(struct inode *inode, struct file *file)
|
|
{
|
|
kfree(file->private_data);
|
|
return 0;
|
|
}
|
|
|
|
static unsigned int eventfd_poll(struct file *file, poll_table *wait)
|
|
{
|
|
struct eventfd_ctx *ctx = file->private_data;
|
|
unsigned int events = 0;
|
|
unsigned long flags;
|
|
|
|
poll_wait(file, &ctx->wqh, wait);
|
|
|
|
spin_lock_irqsave(&ctx->wqh.lock, flags);
|
|
if (ctx->count > 0)
|
|
events |= POLLIN;
|
|
if (ctx->count == ULLONG_MAX)
|
|
events |= POLLERR;
|
|
if (ULLONG_MAX - 1 > ctx->count)
|
|
events |= POLLOUT;
|
|
spin_unlock_irqrestore(&ctx->wqh.lock, flags);
|
|
|
|
return events;
|
|
}
|
|
|
|
static ssize_t eventfd_read(struct file *file, char __user *buf, size_t count,
|
|
loff_t *ppos)
|
|
{
|
|
struct eventfd_ctx *ctx = file->private_data;
|
|
ssize_t res;
|
|
__u64 ucnt;
|
|
DECLARE_WAITQUEUE(wait, current);
|
|
|
|
if (count < sizeof(ucnt))
|
|
return -EINVAL;
|
|
spin_lock_irq(&ctx->wqh.lock);
|
|
res = -EAGAIN;
|
|
ucnt = ctx->count;
|
|
if (ucnt > 0)
|
|
res = sizeof(ucnt);
|
|
else if (!(file->f_flags & O_NONBLOCK)) {
|
|
__add_wait_queue(&ctx->wqh, &wait);
|
|
for (res = 0;;) {
|
|
set_current_state(TASK_INTERRUPTIBLE);
|
|
if (ctx->count > 0) {
|
|
ucnt = ctx->count;
|
|
res = sizeof(ucnt);
|
|
break;
|
|
}
|
|
if (signal_pending(current)) {
|
|
res = -ERESTARTSYS;
|
|
break;
|
|
}
|
|
spin_unlock_irq(&ctx->wqh.lock);
|
|
schedule();
|
|
spin_lock_irq(&ctx->wqh.lock);
|
|
}
|
|
__remove_wait_queue(&ctx->wqh, &wait);
|
|
__set_current_state(TASK_RUNNING);
|
|
}
|
|
if (res > 0) {
|
|
ctx->count = 0;
|
|
if (waitqueue_active(&ctx->wqh))
|
|
wake_up_locked(&ctx->wqh);
|
|
}
|
|
spin_unlock_irq(&ctx->wqh.lock);
|
|
if (res > 0 && put_user(ucnt, (__u64 __user *) buf))
|
|
return -EFAULT;
|
|
|
|
return res;
|
|
}
|
|
|
|
static ssize_t eventfd_write(struct file *file, const char __user *buf, size_t count,
|
|
loff_t *ppos)
|
|
{
|
|
struct eventfd_ctx *ctx = file->private_data;
|
|
ssize_t res;
|
|
__u64 ucnt;
|
|
DECLARE_WAITQUEUE(wait, current);
|
|
|
|
if (count < sizeof(ucnt))
|
|
return -EINVAL;
|
|
if (copy_from_user(&ucnt, buf, sizeof(ucnt)))
|
|
return -EFAULT;
|
|
if (ucnt == ULLONG_MAX)
|
|
return -EINVAL;
|
|
spin_lock_irq(&ctx->wqh.lock);
|
|
res = -EAGAIN;
|
|
if (ULLONG_MAX - ctx->count > ucnt)
|
|
res = sizeof(ucnt);
|
|
else if (!(file->f_flags & O_NONBLOCK)) {
|
|
__add_wait_queue(&ctx->wqh, &wait);
|
|
for (res = 0;;) {
|
|
set_current_state(TASK_INTERRUPTIBLE);
|
|
if (ULLONG_MAX - ctx->count > ucnt) {
|
|
res = sizeof(ucnt);
|
|
break;
|
|
}
|
|
if (signal_pending(current)) {
|
|
res = -ERESTARTSYS;
|
|
break;
|
|
}
|
|
spin_unlock_irq(&ctx->wqh.lock);
|
|
schedule();
|
|
spin_lock_irq(&ctx->wqh.lock);
|
|
}
|
|
__remove_wait_queue(&ctx->wqh, &wait);
|
|
__set_current_state(TASK_RUNNING);
|
|
}
|
|
if (res > 0) {
|
|
ctx->count += ucnt;
|
|
if (waitqueue_active(&ctx->wqh))
|
|
wake_up_locked(&ctx->wqh);
|
|
}
|
|
spin_unlock_irq(&ctx->wqh.lock);
|
|
|
|
return res;
|
|
}
|
|
|
|
static const struct file_operations eventfd_fops = {
|
|
.release = eventfd_release,
|
|
.poll = eventfd_poll,
|
|
.read = eventfd_read,
|
|
.write = eventfd_write,
|
|
};
|
|
|
|
struct file *eventfd_fget(int fd)
|
|
{
|
|
struct file *file;
|
|
|
|
file = fget(fd);
|
|
if (!file)
|
|
return ERR_PTR(-EBADF);
|
|
if (file->f_op != &eventfd_fops) {
|
|
fput(file);
|
|
return ERR_PTR(-EINVAL);
|
|
}
|
|
|
|
return file;
|
|
}
|
|
|
|
asmlinkage long sys_eventfd(unsigned int count)
|
|
{
|
|
int error, fd;
|
|
struct eventfd_ctx *ctx;
|
|
struct file *file;
|
|
struct inode *inode;
|
|
|
|
ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
|
|
if (!ctx)
|
|
return -ENOMEM;
|
|
|
|
init_waitqueue_head(&ctx->wqh);
|
|
ctx->count = count;
|
|
|
|
/*
|
|
* When we call this, the initialization must be complete, since
|
|
* anon_inode_getfd() will install the fd.
|
|
*/
|
|
error = anon_inode_getfd(&fd, &inode, &file, "[eventfd]",
|
|
&eventfd_fops, ctx);
|
|
if (!error)
|
|
return fd;
|
|
|
|
kfree(ctx);
|
|
return error;
|
|
}
|
|
|