Release 4.11 fs/eventfd.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/signal.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/list.h>
#include <linux/spinlock.h>
#include <linux/anon_inodes.h>
#include <linux/syscalls.h>
#include <linux/export.h>
#include <linux/kref.h>
#include <linux/eventfd.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
struct eventfd_ctx {
struct kref kref;
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
* side eventfd_signal() also, adds to the "count" counter and
* issue a wakeup.
*/
__u64 count;
unsigned int flags;
};
/**
* eventfd_signal - Adds @n to the eventfd counter.
* @ctx: [in] Pointer to the eventfd context.
* @n: [in] Value of the counter to be added to the eventfd internal counter.
* The value cannot be negative.
*
* 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 returning a POLLERR
* to poll(2).
*
* Returns the amount by which the counter was incremented. This will be less
* than @n if the counter has overflowed.
*/
__u64 eventfd_signal(struct eventfd_ctx *ctx, __u64 n)
{
unsigned long flags;
spin_lock_irqsave(&ctx->wqh.lock, flags);
if (ULLONG_MAX - ctx->count < n)
n = ULLONG_MAX - ctx->count;
ctx->count += n;
if (waitqueue_active(&ctx->wqh))
wake_up_locked_poll(&ctx->wqh, POLLIN);
spin_unlock_irqrestore(&ctx->wqh.lock, flags);
return n;
}
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| Davide Libenzi | 86 | 97.73% | 4 | 80.00% |
| Sha Zhengju | 2 | 2.27% | 1 | 20.00% |
| Total | 88 | 100.00% | 5 | 100.00% |
EXPORT_SYMBOL_GPL(eventfd_signal);
static void eventfd_free_ctx(struct eventfd_ctx *ctx)
{
kfree(ctx);
}
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| Davide Libenzi | 16 | 100.00% | 1 | 100.00% |
| Total | 16 | 100.00% | 1 | 100.00% |
static void eventfd_free(struct kref *kref)
{
struct eventfd_ctx *ctx = container_of(kref, struct eventfd_ctx, kref);
eventfd_free_ctx(ctx);
}
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| Davide Libenzi | 31 | 100.00% | 2 | 100.00% |
| Total | 31 | 100.00% | 2 | 100.00% |
/**
* eventfd_ctx_get - Acquires a reference to the internal eventfd context.
* @ctx: [in] Pointer to the eventfd context.
*
* Returns: In case of success, returns a pointer to the eventfd context.
*/
struct eventfd_ctx *eventfd_ctx_get(struct eventfd_ctx *ctx)
{
kref_get(&ctx->kref);
return ctx;
}
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| Davide Libenzi | 23 | 100.00% | 1 | 100.00% |
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EXPORT_SYMBOL_GPL(eventfd_ctx_get);
/**
* eventfd_ctx_put - Releases a reference to the internal eventfd context.
* @ctx: [in] Pointer to eventfd context.
*
* The eventfd context reference must have been previously acquired either
* with eventfd_ctx_get() or eventfd_ctx_fdget().
*/
void eventfd_ctx_put(struct eventfd_ctx *ctx)
{
kref_put(&ctx->kref, eventfd_free);
}
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| Davide Libenzi | 20 | 100.00% | 1 | 100.00% |
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EXPORT_SYMBOL_GPL(eventfd_ctx_put);
static int eventfd_release(struct inode *inode, struct file *file)
{
struct eventfd_ctx *ctx = file->private_data;
wake_up_poll(&ctx->wqh, POLLHUP);
eventfd_ctx_put(ctx);
return 0;
}
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static unsigned int eventfd_poll(struct file *file, poll_table *wait)
{
struct eventfd_ctx *ctx = file->private_data;
unsigned int events = 0;
u64 count;
poll_wait(file, &ctx->wqh, wait);
/*
* All writes to ctx->count occur within ctx->wqh.lock. This read
* can be done outside ctx->wqh.lock because we know that poll_wait
* takes that lock (through add_wait_queue) if our caller will sleep.
*
* The read _can_ therefore seep into add_wait_queue's critical
* section, but cannot move above it! add_wait_queue's spin_lock acts
* as an acquire barrier and ensures that the read be ordered properly
* against the writes. The following CAN happen and is safe:
*
* poll write
* ----------------- ------------
* lock ctx->wqh.lock (in poll_wait)
* count = ctx->count
* __add_wait_queue
* unlock ctx->wqh.lock
* lock ctx->qwh.lock
* ctx->count += n
* if (waitqueue_active)
* wake_up_locked_poll
* unlock ctx->qwh.lock
* eventfd_poll returns 0
*
* but the following, which would miss a wakeup, cannot happen:
*
* poll write
* ----------------- ------------
* count = ctx->count (INVALID!)
* lock ctx->qwh.lock
* ctx->count += n
* **waitqueue_active is false**
* **no wake_up_locked_poll!**
* unlock ctx->qwh.lock
* lock ctx->wqh.lock (in poll_wait)
* __add_wait_queue
* unlock ctx->wqh.lock
* eventfd_poll returns 0
*/
count = READ_ONCE(ctx->count);
if (count > 0)
events |= POLLIN;
if (count == ULLONG_MAX)
events |= POLLERR;
if (ULLONG_MAX - 1 > count)
events |= POLLOUT;
return events;
}
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| Paolo Bonzini | 4 | 4.40% | 1 | 33.33% |
| Total | 91 | 100.00% | 3 | 100.00% |
static void eventfd_ctx_do_read(struct eventfd_ctx *ctx, __u64 *cnt)
{
*cnt = (ctx->flags & EFD_SEMAPHORE) ? 1 : ctx->count;
ctx->count -= *cnt;
}
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/**
* eventfd_ctx_remove_wait_queue - Read the current counter and removes wait queue.
* @ctx: [in] Pointer to eventfd context.
* @wait: [in] Wait queue to be removed.
* @cnt: [out] Pointer to the 64-bit counter value.
*
* Returns %0 if successful, or the following error codes:
*
* -EAGAIN : The operation would have blocked.
*
* This is used to atomically remove a wait queue entry from the eventfd wait
* queue head, and read/reset the counter value.
*/
int eventfd_ctx_remove_wait_queue(struct eventfd_ctx *ctx, wait_queue_t *wait,
__u64 *cnt)
{
unsigned long flags;
spin_lock_irqsave(&ctx->wqh.lock, flags);
eventfd_ctx_do_read(ctx, cnt);
__remove_wait_queue(&ctx->wqh, wait);
if (*cnt != 0 && waitqueue_active(&ctx->wqh))
wake_up_locked_poll(&ctx->wqh, POLLOUT);
spin_unlock_irqrestore(&ctx->wqh.lock, flags);
return *cnt != 0 ? 0 : -EAGAIN;
}
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| Total | 99 | 100.00% | 2 | 100.00% |
EXPORT_SYMBOL_GPL(eventfd_ctx_remove_wait_queue);
/**
* eventfd_ctx_read - Reads the eventfd counter or wait if it is zero.
* @ctx: [in] Pointer to eventfd context.
* @no_wait: [in] Different from zero if the operation should not block.
* @cnt: [out] Pointer to the 64-bit counter value.
*
* Returns %0 if successful, or the following error codes:
*
* -EAGAIN : The operation would have blocked but @no_wait was non-zero.
* -ERESTARTSYS : A signal interrupted the wait operation.
*
* If @no_wait is zero, the function might sleep until the eventfd internal
* counter becomes greater than zero.
*/
ssize_t eventfd_ctx_read(struct eventfd_ctx *ctx, int no_wait, __u64 *cnt)
{
ssize_t res;
DECLARE_WAITQUEUE(wait, current);
spin_lock_irq(&ctx->wqh.lock);
*cnt = 0;
res = -EAGAIN;
if (ctx->count > 0)
res = 0;
else if (!no_wait) {
__add_wait_queue(&ctx->wqh, &wait);
for (;;) {
set_current_state(TASK_INTERRUPTIBLE);
if (ctx->count > 0) {
res = 0;
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 (likely(res == 0)) {
eventfd_ctx_do_read(ctx, cnt);
if (waitqueue_active(&ctx->wqh))
wake_up_locked_poll(&ctx->wqh, POLLOUT);
}
spin_unlock_irq(&ctx->wqh.lock);
return res;
}
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| Total | 210 | 100.00% | 5 | 100.00% |
EXPORT_SYMBOL_GPL(eventfd_ctx_read);
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 cnt;
if (count < sizeof(cnt))
return -EINVAL;
res = eventfd_ctx_read(ctx, file->f_flags & O_NONBLOCK, &cnt);
if (res < 0)
return res;
return put_user(cnt, (__u64 __user *) buf) ? -EFAULT : sizeof(cnt);
}
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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 (likely(res > 0)) {
ctx->count += ucnt;
if (waitqueue_active(&ctx->wqh))
wake_up_locked_poll(&ctx->wqh, POLLIN);
}
spin_unlock_irq(&ctx->wqh.lock);
return res;
}
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| Davide Libenzi | 284 | 100.00% | 4 | 100.00% |
| Total | 284 | 100.00% | 4 | 100.00% |
#ifdef CONFIG_PROC_FS
static void eventfd_show_fdinfo(struct seq_file *m, struct file *f)
{
struct eventfd_ctx *ctx = f->private_data;
spin_lock_irq(&ctx->wqh.lock);
seq_printf(m, "eventfd-count: %16llx\n",
(unsigned long long)ctx->count);
spin_unlock_irq(&ctx->wqh.lock);
}
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| Person | Tokens | Prop | Commits | CommitProp |
| Cyrill V. Gorcunov | 60 | 98.36% | 1 | 50.00% |
| Joe Perches | 1 | 1.64% | 1 | 50.00% |
| Total | 61 | 100.00% | 2 | 100.00% |
#endif
static const struct file_operations eventfd_fops = {
#ifdef CONFIG_PROC_FS
.show_fdinfo = eventfd_show_fdinfo,
#endif
.release = eventfd_release,
.poll = eventfd_poll,
.read = eventfd_read,
.write = eventfd_write,
.llseek = noop_llseek,
};
/**
* eventfd_fget - Acquire a reference of an eventfd file descriptor.
* @fd: [in] Eventfd file descriptor.
*
* Returns a pointer to the eventfd file structure in case of success, or the
* following error pointer:
*
* -EBADF : Invalid @fd file descriptor.
* -EINVAL : The @fd file descriptor is not an eventfd file.
*/
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;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Davide Libenzi | 60 | 100.00% | 1 | 100.00% |
| Total | 60 | 100.00% | 1 | 100.00% |
EXPORT_SYMBOL_GPL(eventfd_fget);
/**
* eventfd_ctx_fdget - Acquires a reference to the internal eventfd context.
* @fd: [in] Eventfd file descriptor.
*
* Returns a pointer to the internal eventfd context, otherwise the error
* pointers returned by the following functions:
*
* eventfd_fget
*/
struct eventfd_ctx *eventfd_ctx_fdget(int fd)
{
struct eventfd_ctx *ctx;
struct fd f = fdget(fd);
if (!f.file)
return ERR_PTR(-EBADF);
ctx = eventfd_ctx_fileget(f.file);
fdput(f);
return ctx;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Davide Libenzi | 36 | 65.45% | 1 | 50.00% |
| Al Viro | 19 | 34.55% | 1 | 50.00% |
| Total | 55 | 100.00% | 2 | 100.00% |
EXPORT_SYMBOL_GPL(eventfd_ctx_fdget);
/**
* eventfd_ctx_fileget - Acquires a reference to the internal eventfd context.
* @file: [in] Eventfd file pointer.
*
* Returns a pointer to the internal eventfd context, otherwise the error
* pointer:
*
* -EINVAL : The @fd file descriptor is not an eventfd file.
*/
struct eventfd_ctx *eventfd_ctx_fileget(struct file *file)
{
if (file->f_op != &eventfd_fops)
return ERR_PTR(-EINVAL);
return eventfd_ctx_get(file->private_data);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Davide Libenzi | 36 | 100.00% | 1 | 100.00% |
| Total | 36 | 100.00% | 1 | 100.00% |
EXPORT_SYMBOL_GPL(eventfd_ctx_fileget);
/**
* eventfd_file_create - Creates an eventfd file pointer.
* @count: Initial eventfd counter value.
* @flags: Flags for the eventfd file.
*
* This function creates an eventfd file pointer, w/out installing it into
* the fd table. This is useful when the eventfd file is used during the
* initialization of data structures that require extra setup after the eventfd
* creation. So the eventfd creation is split into the file pointer creation
* phase, and the file descriptor installation phase.
* In this way races with userspace closing the newly installed file descriptor
* can be avoided.
* Returns an eventfd file pointer, or a proper error pointer.
*/
struct file *eventfd_file_create(unsigned int count, int flags)
{
struct file *file;
struct eventfd_ctx *ctx;
/* Check the EFD_* constants for consistency. */
BUILD_BUG_ON(EFD_CLOEXEC != O_CLOEXEC);
BUILD_BUG_ON(EFD_NONBLOCK != O_NONBLOCK);
if (flags & ~EFD_FLAGS_SET)
return ERR_PTR(-EINVAL);
ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
if (!ctx)
return ERR_PTR(-ENOMEM);
kref_init(&ctx->kref);
init_waitqueue_head(&ctx->wqh);
ctx->count = count;
ctx->flags = flags;
file = anon_inode_getfile("[eventfd]", &eventfd_fops, ctx,
O_RDWR | (flags & EFD_SHARED_FCNTL_FLAGS));
if (IS_ERR(file))
eventfd_free_ctx(ctx);
return file;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Davide Libenzi | 109 | 77.30% | 4 | 50.00% |
| Ulrich Drepper | 28 | 19.86% | 3 | 37.50% |
| Roland Dreier | 4 | 2.84% | 1 | 12.50% |
| Total | 141 | 100.00% | 8 | 100.00% |
SYSCALL_DEFINE2(eventfd2, unsigned int, count, int, flags)
{
int fd, error;
struct file *file;
error = get_unused_fd_flags(flags & EFD_SHARED_FCNTL_FLAGS);
if (error < 0)
return error;
fd = error;
file = eventfd_file_create(count, flags);
if (IS_ERR(file)) {
error = PTR_ERR(file);
goto err_put_unused_fd;
}
fd_install(fd, file);
return fd;
err_put_unused_fd:
put_unused_fd(fd);
return error;
}
SYSCALL_DEFINE1(eventfd, unsigned int, count)
{
return sys_eventfd2(count, 0);
}
Overall Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Davide Libenzi | 1478 | 88.40% | 7 | 25.93% |
| Cyrill V. Gorcunov | 81 | 4.84% | 1 | 3.70% |
| Ulrich Drepper | 38 | 2.27% | 3 | 11.11% |
| Al Viro | 23 | 1.38% | 2 | 7.41% |
| Rusty Russell | 12 | 0.72% | 1 | 3.70% |
| Heiko Carstens | 8 | 0.48% | 1 | 3.70% |
| Chris Mason | 5 | 0.30% | 1 | 3.70% |
| Arnd Bergmann | 5 | 0.30% | 1 | 3.70% |
| Paolo Bonzini | 4 | 0.24% | 1 | 3.70% |
| Roland Dreier | 4 | 0.24% | 1 | 3.70% |
| Tejun Heo | 3 | 0.18% | 1 | 3.70% |
| Randy Dunlap | 3 | 0.18% | 1 | 3.70% |
| Adrian Bunk | 2 | 0.12% | 1 | 3.70% |
| Sha Zhengju | 2 | 0.12% | 1 | 3.70% |
| Ingo Molnar | 1 | 0.06% | 1 | 3.70% |
| Joe Perches | 1 | 0.06% | 1 | 3.70% |
| Masanari Iida | 1 | 0.06% | 1 | 3.70% |
| Paul Gortmaker | 1 | 0.06% | 1 | 3.70% |
| Total | 1672 | 100.00% | 27 | 100.00% |
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