* [PATCH v2 0/1] Generalize poll events from eventfd
@ 2015-09-16 6:27 Damian Hobson-Garcia
[not found] ` <1442384836-13045-1-git-send-email-dhobsong-AlSX/UN32fvPDbFq/vQRIQ@public.gmane.org>
0 siblings, 1 reply; 4+ messages in thread
From: Damian Hobson-Garcia @ 2015-09-16 6:27 UTC (permalink / raw
To: viro, sustrik
Cc: linux-kernel, linux-fsdevel, linux-api, netdev, David.Laight,
Damian Hobson-Garcia
Using eventfd user space can generate POLLIN/POLLOUT events but some
applications may want to generate POLLPRI/POLLERR events as well.
This patch submission aims to generalize the events generated by an
eventfd. This is a resubmission of a patch from Feb 2013[1]. The original
discussion trailed off without any conclusion, but the original author
has recently confirmed[2] that this functionality is still useful, so I
volunteered to rebase and resubmit the patch for discussion.
[1] https://lkml.org/lkml/2013/2/18/147
[2] https://lkml.org/lkml/2015/7/9/153
Changes in v2
-------------
* rebased on Linux v4.3-rc1
* Move file operation implementations for EFD_MASK to a seperate structure
* Remove 'data' element from efd_mask structure
* read() is no longer supported when EFD_MASK is set (fails with EINVAL)
* eventfd_ctx_fileget() now returns EINVAL when EFD_MASK is set, eliminating
the possibility of triggering the orginal BUG_ON() macros which have now
been removed.
Thank you,
Damian
Martin Sustrik (1):
eventfd: implementation of EFD_MASK flag
fs/eventfd.c | 91 ++++++++++++++++++++++++++++++++++++++------
include/linux/eventfd.h | 16 +-------
include/uapi/linux/eventfd.h | 40 +++++++++++++++++++
3 files changed, 121 insertions(+), 26 deletions(-)
create mode 100644 include/uapi/linux/eventfd.h
--
1.9.1
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH v2 1/1] eventfd: implementation of EFD_MASK flag
[not found] ` <1442384836-13045-1-git-send-email-dhobsong-AlSX/UN32fvPDbFq/vQRIQ@public.gmane.org>
@ 2015-09-16 6:27 ` Damian Hobson-Garcia
2015-09-16 6:51 ` Martin Sustrik
0 siblings, 1 reply; 4+ messages in thread
From: Damian Hobson-Garcia @ 2015-09-16 6:27 UTC (permalink / raw
To: viro-RmSDqhL/yNMiFSDQTTA3OLVCufUGDwFn,
sustrik-8XN41Hm7QBXQT0dZR+AlfA
Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA,
linux-fsdevel-u79uwXL29TY76Z2rM5mHXA,
linux-api-u79uwXL29TY76Z2rM5mHXA, netdev-u79uwXL29TY76Z2rM5mHXA,
David.Laight-JxhZ9S5GRejQT0dZR+AlfA, Damian Hobson-Garcia
From: Martin Sustrik <sustrik-8XN41Hm7QBXQT0dZR+AlfA@public.gmane.org>
When implementing network protocols in user space, one has to implement
fake file descriptors to represent the sockets for the protocol.
Polling on such fake file descriptors is a problem (poll/select/epoll
accept only true file descriptors) and forces protocol implementers to use
various workarounds resulting in complex, non-standard and convoluted APIs.
More generally, ability to create full-blown file descriptors for
userspace-to-userspace signalling is missing. While eventfd(2) goes half
the way towards this goal it has follwoing shorcomings:
I. There's no way to signal POLLPRI, POLLHUP etc.
II. There's no way to signal arbitrary combination of POLL* flags. Most
notably, simultaneous !POLLIN and !POLLOUT, which is a perfectly valid
combination for a network protocol (rx buffer is empty and tx buffer is
full), cannot be signaled using eventfd.
This patch implements new EFD_MASK flag which solves the above problems.
Additionally, to provide a way to associate user-space state with eventfd
object, it allows to attach user-space data to the file descriptor.
The semantics of EFD_MASK are as follows:
eventfd(2):
If eventfd is created with EFD_MASK flag set, it is initialised in such a
way as to signal no events on the file descriptor when it is polled on.
The 'initval' argument is ignored.
write(2):
User is allowed to write only buffers containing the following structure:
struct efd_mask {
uint32_t events;
};
The value of 'events' should be any combination of event flags as defined
by poll(2) function (POLLIN, POLLOUT, POLLERR, POLLHUP etc.) Specified
events will be signaled when polling (select, poll, epoll) on the eventfd
is done later on.
read(2):
read is not supported and will fail with EINVAL.
select(2), poll(2) and similar:
When polling on the eventfd marked by EFD_MASK flag, all the events
specified in last written 'events' field shall be signaled.
Signed-off-by: Martin Sustrik <sustrik-8XN41Hm7QBXQT0dZR+AlfA@public.gmane.org>
[dhobsong-AlSX/UN32fvPDbFq/vQRIQ@public.gmane.org: Rebased, and resubmitted for Linux 4.3]
Signed-off-by: Damian Hobson-Garcia <dhobsong-AlSX/UN32fvPDbFq/vQRIQ@public.gmane.org>
---
fs/eventfd.c | 102 ++++++++++++++++++++++++++++++++++++++-----
include/linux/eventfd.h | 16 +------
include/uapi/linux/eventfd.h | 39 +++++++++++++++++
3 files changed, 132 insertions(+), 25 deletions(-)
create mode 100644 include/uapi/linux/eventfd.h
diff --git a/fs/eventfd.c b/fs/eventfd.c
index 8d0c0df..1a6a066 100644
--- a/fs/eventfd.c
+++ b/fs/eventfd.c
@@ -2,6 +2,7 @@
* fs/eventfd.c
*
* Copyright (C) 2007 Davide Libenzi <davidel-AhlLAIvw+VEjIGhXcJzhZg@public.gmane.org>
+ * Copyright (C) 2013 Martin Sustrik <sustrik-8XN41Hm7QBXQT0dZR+AlfA@public.gmane.org>
*
*/
@@ -22,18 +23,31 @@
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
+#define EFD_SHARED_FCNTL_FLAGS (O_CLOEXEC | O_NONBLOCK)
+#define EFD_FLAGS_SET (EFD_SHARED_FCNTL_FLAGS | EFD_SEMAPHORE | EFD_MASK)
+#define EFD_MASK_VALID_EVENTS (POLLIN | POLLPRI | POLLOUT | POLLERR | POLLHUP)
+
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;
+ union {
+ /*
+ * 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;
+
+ /*
+ * When using eventfd in EFD_MASK mode this stracture stores the
+ * current events to be signaled on the eventfd (events member)
+ * along with opaque user-defined data (data member).
+ */
+ struct efd_mask mask;
+ };
unsigned int flags;
};
@@ -134,6 +148,14 @@ static unsigned int eventfd_poll(struct file *file, poll_table *wait)
return events;
}
+static unsigned int eventfd_mask_poll(struct file *file, poll_table *wait)
+{
+ struct eventfd_ctx *ctx = file->private_data;
+
+ poll_wait(file, &ctx->wqh, wait);
+ return ctx->mask.events;
+}
+
static void eventfd_ctx_do_read(struct eventfd_ctx *ctx, __u64 *cnt)
{
*cnt = (ctx->flags & EFD_SEMAPHORE) ? 1 : ctx->count;
@@ -239,6 +261,14 @@ static ssize_t eventfd_read(struct file *file, char __user *buf, size_t count,
return put_user(cnt, (__u64 __user *) buf) ? -EFAULT : sizeof(cnt);
}
+static ssize_t eventfd_mask_read(struct file *file, char __user *buf,
+ size_t count,
+ loff_t *ppos)
+{
+ return -EINVAL;
+}
+
+
static ssize_t eventfd_write(struct file *file, const char __user *buf, size_t count,
loff_t *ppos)
{
@@ -286,6 +316,28 @@ static ssize_t eventfd_write(struct file *file, const char __user *buf, size_t c
return res;
}
+static ssize_t eventfd_mask_write(struct file *file, const char __user *buf,
+ size_t count,
+ loff_t *ppos)
+{
+ struct eventfd_ctx *ctx = file->private_data;
+ struct efd_mask mask;
+
+ if (count < sizeof(mask))
+ return -EINVAL;
+ if (copy_from_user(&mask, buf, sizeof(mask)))
+ return -EFAULT;
+ if (mask.events & ~EFD_MASK_VALID_EVENTS)
+ return -EINVAL;
+ spin_lock_irq(&ctx->wqh.lock);
+ memcpy(&ctx->mask, &mask, sizeof(ctx->mask));
+ if (waitqueue_active(&ctx->wqh))
+ wake_up_locked_poll(&ctx->wqh,
+ (unsigned long)ctx->mask.events);
+ spin_unlock_irq(&ctx->wqh.lock);
+ return sizeof(ctx->mask);
+}
+
#ifdef CONFIG_PROC_FS
static void eventfd_show_fdinfo(struct seq_file *m, struct file *f)
{
@@ -296,6 +348,16 @@ static void eventfd_show_fdinfo(struct seq_file *m, struct file *f)
(unsigned long long)ctx->count);
spin_unlock_irq(&ctx->wqh.lock);
}
+
+static void eventfd_mask_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-mask: %x\n",
+ (unsigned)ctx->mask.events);
+ spin_unlock_irq(&ctx->wqh.lock);
+}
#endif
static const struct file_operations eventfd_fops = {
@@ -309,6 +371,17 @@ static const struct file_operations eventfd_fops = {
.llseek = noop_llseek,
};
+static const struct file_operations eventfd_mask_fops = {
+#ifdef CONFIG_PROC_FS
+ .show_fdinfo = eventfd_mask_show_fdinfo,
+#endif
+ .release = eventfd_release,
+ .poll = eventfd_mask_poll,
+ .read = eventfd_mask_read,
+ .write = eventfd_mask_write,
+ .llseek = noop_llseek,
+};
+
/**
* eventfd_fget - Acquire a reference of an eventfd file descriptor.
* @fd: [in] Eventfd file descriptor.
@@ -392,6 +465,7 @@ struct file *eventfd_file_create(unsigned int count, int flags)
{
struct file *file;
struct eventfd_ctx *ctx;
+ const struct file_operations *fops;
/* Check the EFD_* constants for consistency. */
BUILD_BUG_ON(EFD_CLOEXEC != O_CLOEXEC);
@@ -406,10 +480,16 @@ struct file *eventfd_file_create(unsigned int count, int flags)
kref_init(&ctx->kref);
init_waitqueue_head(&ctx->wqh);
- ctx->count = count;
+ if (flags & EFD_MASK) {
+ memset(&ctx->mask, 0, sizeof(ctx->mask));
+ fops = &eventfd_mask_fops;
+ } else {
+ ctx->count = count;
+ fops = &eventfd_fops;
+ }
ctx->flags = flags;
- file = anon_inode_getfile("[eventfd]", &eventfd_fops, ctx,
+ file = anon_inode_getfile("[eventfd]", fops, ctx,
O_RDWR | (flags & EFD_SHARED_FCNTL_FLAGS));
if (IS_ERR(file))
eventfd_free_ctx(ctx);
diff --git a/include/linux/eventfd.h b/include/linux/eventfd.h
index ff0b981..87de343 100644
--- a/include/linux/eventfd.h
+++ b/include/linux/eventfd.h
@@ -8,23 +8,11 @@
#ifndef _LINUX_EVENTFD_H
#define _LINUX_EVENTFD_H
+#include <uapi/linux/eventfd.h>
+
#include <linux/fcntl.h>
#include <linux/wait.h>
-/*
- * CAREFUL: Check include/uapi/asm-generic/fcntl.h when defining
- * new flags, since they might collide with O_* ones. We want
- * to re-use O_* flags that couldn't possibly have a meaning
- * from eventfd, in order to leave a free define-space for
- * shared O_* flags.
- */
-#define EFD_SEMAPHORE (1 << 0)
-#define EFD_CLOEXEC O_CLOEXEC
-#define EFD_NONBLOCK O_NONBLOCK
-
-#define EFD_SHARED_FCNTL_FLAGS (O_CLOEXEC | O_NONBLOCK)
-#define EFD_FLAGS_SET (EFD_SHARED_FCNTL_FLAGS | EFD_SEMAPHORE)
-
struct file;
#ifdef CONFIG_EVENTFD
diff --git a/include/uapi/linux/eventfd.h b/include/uapi/linux/eventfd.h
new file mode 100644
index 0000000..98ec034
--- /dev/null
+++ b/include/uapi/linux/eventfd.h
@@ -0,0 +1,39 @@
+/*
+ * Copyright (C) 2013 Martin Sustrik <sustrik-8XN41Hm7QBXQT0dZR+AlfA@public.gmane.org>
+ *
+ * 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.
+ */
+
+#ifndef _UAPI_LINUX_EVENTFD_H
+#define _UAPI_LINUX_EVENTFD_H
+
+/* For O_CLOEXEC */
+#include <linux/fcntl.h>
+#include <linux/types.h>
+
+/*
+ * CAREFUL: Check include/asm-generic/fcntl.h when defining
+ * new flags, since they might collide with O_* ones. We want
+ * to re-use O_* flags that couldn't possibly have a meaning
+ * from eventfd, in order to leave a free define-space for
+ * shared O_* flags.
+ */
+
+/* Provide semaphore-like semantics for reads from the eventfd. */
+#define EFD_SEMAPHORE (1 << 0)
+/* Provide event mask semantics for the eventfd. */
+#define EFD_MASK (1 << 1)
+/* Set the close-on-exec (FD_CLOEXEC) flag on the eventfd. */
+#define EFD_CLOEXEC O_CLOEXEC
+/* Create the eventfd in non-blocking mode. */
+#define EFD_NONBLOCK O_NONBLOCK
+
+/* Structure to read/write to eventfd in EFD_MASK mode. */
+struct efd_mask {
+ __u32 events;
+};
+
+#endif /* _UAPI_LINUX_EVENTFD_H */
--
1.9.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH v2 1/1] eventfd: implementation of EFD_MASK flag
2015-09-16 6:27 ` [PATCH v2 1/1] eventfd: implementation of EFD_MASK flag Damian Hobson-Garcia
@ 2015-09-16 6:51 ` Martin Sustrik
2015-09-16 7:43 ` Damian Hobson-Garcia
0 siblings, 1 reply; 4+ messages in thread
From: Martin Sustrik @ 2015-09-16 6:51 UTC (permalink / raw
To: Damian Hobson-Garcia
Cc: viro, linux-kernel, linux-fsdevel, linux-api, netdev,
David.Laight
On 2015-09-16 08:27, Damian Hobson-Garcia wrote:
> From: Martin Sustrik <sustrik@250bpm.com>
>
> When implementing network protocols in user space, one has to implement
> fake file descriptors to represent the sockets for the protocol.
>
> Polling on such fake file descriptors is a problem (poll/select/epoll
> accept only true file descriptors) and forces protocol implementers to
> use
> various workarounds resulting in complex, non-standard and convoluted
> APIs.
>
> More generally, ability to create full-blown file descriptors for
> userspace-to-userspace signalling is missing. While eventfd(2) goes
> half
> the way towards this goal it has follwoing shorcomings:
>
> I. There's no way to signal POLLPRI, POLLHUP etc.
> II. There's no way to signal arbitrary combination of POLL* flags. Most
> notably, simultaneous !POLLIN and !POLLOUT, which is a perfectly
> valid
> combination for a network protocol (rx buffer is empty and tx
> buffer is
> full), cannot be signaled using eventfd.
>
> This patch implements new EFD_MASK flag which solves the above
> problems.
>
> Additionally, to provide a way to associate user-space state with
> eventfd
> object, it allows to attach user-space data to the file descriptor.
The above paragraph is a leftover from the past. The functionality no
longer exist.
>
> The semantics of EFD_MASK are as follows:
>
> eventfd(2):
>
> If eventfd is created with EFD_MASK flag set, it is initialised in such
> a
> way as to signal no events on the file descriptor when it is polled on.
> The 'initval' argument is ignored.
>
> write(2):
>
> User is allowed to write only buffers containing the following
> structure:
>
> struct efd_mask {
> uint32_t events;
> };
Is it worth having a struct here? Why not just uint32_t?
Martin
>
> The value of 'events' should be any combination of event flags as
> defined
> by poll(2) function (POLLIN, POLLOUT, POLLERR, POLLHUP etc.) Specified
> events will be signaled when polling (select, poll, epoll) on the
> eventfd
> is done later on.
>
> read(2):
>
> read is not supported and will fail with EINVAL.
>
> select(2), poll(2) and similar:
>
> When polling on the eventfd marked by EFD_MASK flag, all the events
> specified in last written 'events' field shall be signaled.
>
> Signed-off-by: Martin Sustrik <sustrik@250bpm.com>
>
> [dhobsong@igel.co.jp: Rebased, and resubmitted for Linux 4.3]
> Signed-off-by: Damian Hobson-Garcia <dhobsong@igel.co.jp>
> ---
> fs/eventfd.c | 102
> ++++++++++++++++++++++++++++++++++++++-----
> include/linux/eventfd.h | 16 +------
> include/uapi/linux/eventfd.h | 39 +++++++++++++++++
> 3 files changed, 132 insertions(+), 25 deletions(-)
> create mode 100644 include/uapi/linux/eventfd.h
>
> diff --git a/fs/eventfd.c b/fs/eventfd.c
> index 8d0c0df..1a6a066 100644
> --- a/fs/eventfd.c
> +++ b/fs/eventfd.c
> @@ -2,6 +2,7 @@
> * fs/eventfd.c
> *
> * Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org>
> + * Copyright (C) 2013 Martin Sustrik <sustrik@250bpm.com>
> *
> */
>
> @@ -22,18 +23,31 @@
> #include <linux/proc_fs.h>
> #include <linux/seq_file.h>
>
> +#define EFD_SHARED_FCNTL_FLAGS (O_CLOEXEC | O_NONBLOCK)
> +#define EFD_FLAGS_SET (EFD_SHARED_FCNTL_FLAGS | EFD_SEMAPHORE |
> EFD_MASK)
> +#define EFD_MASK_VALID_EVENTS (POLLIN | POLLPRI | POLLOUT | POLLERR |
> POLLHUP)
> +
> 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;
> + union {
> + /*
> + * 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;
> +
> + /*
> + * When using eventfd in EFD_MASK mode this stracture stores the
> + * current events to be signaled on the eventfd (events member)
> + * along with opaque user-defined data (data member).
> + */
> + struct efd_mask mask;
> + };
> unsigned int flags;
> };
>
> @@ -134,6 +148,14 @@ static unsigned int eventfd_poll(struct file
> *file, poll_table *wait)
> return events;
> }
>
> +static unsigned int eventfd_mask_poll(struct file *file, poll_table
> *wait)
> +{
> + struct eventfd_ctx *ctx = file->private_data;
> +
> + poll_wait(file, &ctx->wqh, wait);
> + return ctx->mask.events;
> +}
> +
> static void eventfd_ctx_do_read(struct eventfd_ctx *ctx, __u64 *cnt)
> {
> *cnt = (ctx->flags & EFD_SEMAPHORE) ? 1 : ctx->count;
> @@ -239,6 +261,14 @@ static ssize_t eventfd_read(struct file *file,
> char __user *buf, size_t count,
> return put_user(cnt, (__u64 __user *) buf) ? -EFAULT : sizeof(cnt);
> }
>
> +static ssize_t eventfd_mask_read(struct file *file, char __user *buf,
> + size_t count,
> + loff_t *ppos)
> +{
> + return -EINVAL;
> +}
> +
> +
> static ssize_t eventfd_write(struct file *file, const char __user
> *buf, size_t count,
> loff_t *ppos)
> {
> @@ -286,6 +316,28 @@ static ssize_t eventfd_write(struct file *file,
> const char __user *buf, size_t c
> return res;
> }
>
> +static ssize_t eventfd_mask_write(struct file *file, const char __user
> *buf,
> + size_t count,
> + loff_t *ppos)
> +{
> + struct eventfd_ctx *ctx = file->private_data;
> + struct efd_mask mask;
> +
> + if (count < sizeof(mask))
> + return -EINVAL;
> + if (copy_from_user(&mask, buf, sizeof(mask)))
> + return -EFAULT;
> + if (mask.events & ~EFD_MASK_VALID_EVENTS)
> + return -EINVAL;
> + spin_lock_irq(&ctx->wqh.lock);
> + memcpy(&ctx->mask, &mask, sizeof(ctx->mask));
> + if (waitqueue_active(&ctx->wqh))
> + wake_up_locked_poll(&ctx->wqh,
> + (unsigned long)ctx->mask.events);
> + spin_unlock_irq(&ctx->wqh.lock);
> + return sizeof(ctx->mask);
> +}
> +
> #ifdef CONFIG_PROC_FS
> static void eventfd_show_fdinfo(struct seq_file *m, struct file *f)
> {
> @@ -296,6 +348,16 @@ static void eventfd_show_fdinfo(struct seq_file
> *m, struct file *f)
> (unsigned long long)ctx->count);
> spin_unlock_irq(&ctx->wqh.lock);
> }
> +
> +static void eventfd_mask_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-mask: %x\n",
> + (unsigned)ctx->mask.events);
> + spin_unlock_irq(&ctx->wqh.lock);
> +}
> #endif
>
> static const struct file_operations eventfd_fops = {
> @@ -309,6 +371,17 @@ static const struct file_operations eventfd_fops =
> {
> .llseek = noop_llseek,
> };
>
> +static const struct file_operations eventfd_mask_fops = {
> +#ifdef CONFIG_PROC_FS
> + .show_fdinfo = eventfd_mask_show_fdinfo,
> +#endif
> + .release = eventfd_release,
> + .poll = eventfd_mask_poll,
> + .read = eventfd_mask_read,
> + .write = eventfd_mask_write,
> + .llseek = noop_llseek,
> +};
> +
> /**
> * eventfd_fget - Acquire a reference of an eventfd file descriptor.
> * @fd: [in] Eventfd file descriptor.
> @@ -392,6 +465,7 @@ struct file *eventfd_file_create(unsigned int
> count, int flags)
> {
> struct file *file;
> struct eventfd_ctx *ctx;
> + const struct file_operations *fops;
>
> /* Check the EFD_* constants for consistency. */
> BUILD_BUG_ON(EFD_CLOEXEC != O_CLOEXEC);
> @@ -406,10 +480,16 @@ struct file *eventfd_file_create(unsigned int
> count, int flags)
>
> kref_init(&ctx->kref);
> init_waitqueue_head(&ctx->wqh);
> - ctx->count = count;
> + if (flags & EFD_MASK) {
> + memset(&ctx->mask, 0, sizeof(ctx->mask));
> + fops = &eventfd_mask_fops;
> + } else {
> + ctx->count = count;
> + fops = &eventfd_fops;
> + }
> ctx->flags = flags;
>
> - file = anon_inode_getfile("[eventfd]", &eventfd_fops, ctx,
> + file = anon_inode_getfile("[eventfd]", fops, ctx,
> O_RDWR | (flags & EFD_SHARED_FCNTL_FLAGS));
> if (IS_ERR(file))
> eventfd_free_ctx(ctx);
> diff --git a/include/linux/eventfd.h b/include/linux/eventfd.h
> index ff0b981..87de343 100644
> --- a/include/linux/eventfd.h
> +++ b/include/linux/eventfd.h
> @@ -8,23 +8,11 @@
> #ifndef _LINUX_EVENTFD_H
> #define _LINUX_EVENTFD_H
>
> +#include <uapi/linux/eventfd.h>
> +
> #include <linux/fcntl.h>
> #include <linux/wait.h>
>
> -/*
> - * CAREFUL: Check include/uapi/asm-generic/fcntl.h when defining
> - * new flags, since they might collide with O_* ones. We want
> - * to re-use O_* flags that couldn't possibly have a meaning
> - * from eventfd, in order to leave a free define-space for
> - * shared O_* flags.
> - */
> -#define EFD_SEMAPHORE (1 << 0)
> -#define EFD_CLOEXEC O_CLOEXEC
> -#define EFD_NONBLOCK O_NONBLOCK
> -
> -#define EFD_SHARED_FCNTL_FLAGS (O_CLOEXEC | O_NONBLOCK)
> -#define EFD_FLAGS_SET (EFD_SHARED_FCNTL_FLAGS | EFD_SEMAPHORE)
> -
> struct file;
>
> #ifdef CONFIG_EVENTFD
> diff --git a/include/uapi/linux/eventfd.h
> b/include/uapi/linux/eventfd.h
> new file mode 100644
> index 0000000..98ec034
> --- /dev/null
> +++ b/include/uapi/linux/eventfd.h
> @@ -0,0 +1,39 @@
> +/*
> + * Copyright (C) 2013 Martin Sustrik <sustrik@250bpm.com>
> + *
> + * 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.
> + */
> +
> +#ifndef _UAPI_LINUX_EVENTFD_H
> +#define _UAPI_LINUX_EVENTFD_H
> +
> +/* For O_CLOEXEC */
> +#include <linux/fcntl.h>
> +#include <linux/types.h>
> +
> +/*
> + * CAREFUL: Check include/asm-generic/fcntl.h when defining
> + * new flags, since they might collide with O_* ones. We want
> + * to re-use O_* flags that couldn't possibly have a meaning
> + * from eventfd, in order to leave a free define-space for
> + * shared O_* flags.
> + */
> +
> +/* Provide semaphore-like semantics for reads from the eventfd. */
> +#define EFD_SEMAPHORE (1 << 0)
> +/* Provide event mask semantics for the eventfd. */
> +#define EFD_MASK (1 << 1)
> +/* Set the close-on-exec (FD_CLOEXEC) flag on the eventfd. */
> +#define EFD_CLOEXEC O_CLOEXEC
> +/* Create the eventfd in non-blocking mode. */
> +#define EFD_NONBLOCK O_NONBLOCK
> +
> +/* Structure to read/write to eventfd in EFD_MASK mode. */
> +struct efd_mask {
> + __u32 events;
> +};
> +
> +#endif /* _UAPI_LINUX_EVENTFD_H */
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v2 1/1] eventfd: implementation of EFD_MASK flag
2015-09-16 6:51 ` Martin Sustrik
@ 2015-09-16 7:43 ` Damian Hobson-Garcia
0 siblings, 0 replies; 4+ messages in thread
From: Damian Hobson-Garcia @ 2015-09-16 7:43 UTC (permalink / raw
To: Martin Sustrik
Cc: viro, linux-kernel, linux-fsdevel, linux-api, netdev,
David.Laight
Hi Martin,
On 2015-09-16 3:51 PM, Martin Sustrik wrote:
> On 2015-09-16 08:27, Damian Hobson-Garcia wrote:
>>
>> Additionally, to provide a way to associate user-space state with eventfd
>> object, it allows to attach user-space data to the file descriptor.
>
> The above paragraph is a leftover from the past. The functionality no
> longer exist.
>
Oops, I forgot to delete that part. I'll get rid of it.
>>
>> The semantics of EFD_MASK are as follows:
>>
>> eventfd(2):
>>
>> If eventfd is created with EFD_MASK flag set, it is initialised in such a
>> way as to signal no events on the file descriptor when it is polled on.
>> The 'initval' argument is ignored.
>>
>> write(2):
>>
>> User is allowed to write only buffers containing the following structure:
>>
>> struct efd_mask {
>> uint32_t events;
>> };
>
> Is it worth having a struct here? Why not just uint32_t?
As it stands right now, no, the struct doesn't really add anything.
uint32_t should be just fine.
>
> Martin
Damian
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2015-09-16 7:43 UTC | newest]
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2015-09-16 6:27 [PATCH v2 0/1] Generalize poll events from eventfd Damian Hobson-Garcia
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2015-09-16 6:27 ` [PATCH v2 1/1] eventfd: implementation of EFD_MASK flag Damian Hobson-Garcia
2015-09-16 6:51 ` Martin Sustrik
2015-09-16 7:43 ` Damian Hobson-Garcia
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