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Date: Mon, 11 Dec 2006 12:32:55 -0400
From: "Mauricio Lin" <mauriciolin@...il.com>
To: "Evgeniy Polyakov" <johnpol@....mipt.ru>
Cc: "David Miller" <davem@...emloft.net>,
"Ulrich Drepper" <drepper@...hat.com>,
"Andrew Morton" <akpm@...l.org>, netdev <netdev@...r.kernel.org>,
"Zach Brown" <zach.brown@...cle.com>,
"Christoph Hellwig" <hch@...radead.org>,
"Chase Venters" <chase.venters@...entec.com>,
"Johann Borck" <johann.borck@...sedata.com>,
linux-kernel@...r.kernel.org, "Jeff Garzik" <jeff@...zik.org>
Subject: Re: [take26-resend1 7/8] kevent: Signal notifications.
Hi Evgeniy,
I have used kobject_uevent() to notify userspace about some events.
For instance, when memory comsumption reaches a predefined watermark,
a signal is sent to userspace to allow applications to free resources.
But I am not sure if kobject_uevent() is the more appropriate way for
that since if I have many different levels of notifications (using
kobject_uevent()) from kernel space to user space, so how the
application could know or differentiate from which level of kernel
notification the signal was sent from?
The application should perform a specific task according to different
type of received notification. So I do not know if the current kernel
provides something like that. Do you know any current kernel (2.6.19)
implementation for that?
After reading about your Kevent implementation, I guess that your
patches are able to do what I need, right? Will it be included in the
mainline kernel? Do you have examples about how can I use your socket
and/or signal notifications to establish kernel and user space
communication?
BR,
Mauricio Lin.
On 12/11/06, Evgeniy Polyakov <johnpol@....mipt.ru> wrote:
>
> Signal notifications.
>
> This type of notifications allows to deliver signals through kevent queue.
> One can find example application signal.c on project homepage.
>
> If KEVENT_SIGNAL_NOMASK bit is set in raw_u64 id then signal will be
> delivered only through queue, otherwise both delivery types are used - old
> through update of mask of pending signals and through queue.
>
> If signal is delivered only through kevent queue mask of pending signals
> is not updated at all, which is equal to putting signal into blocked mask,
> but with delivery of that signal through kevent queue.
>
> Signed-off-by: Evgeniy Polyakov <johnpol@....mipt.ru>
>
>
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index fc4a987..ef38a3c 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -80,6 +80,7 @@ struct sched_param {
> #include <linux/resource.h>
> #include <linux/timer.h>
> #include <linux/hrtimer.h>
> +#include <linux/kevent_storage.h>
>
> #include <asm/processor.h>
>
> @@ -1013,6 +1014,10 @@ struct task_struct {
> #ifdef CONFIG_TASK_DELAY_ACCT
> struct task_delay_info *delays;
> #endif
> +#ifdef CONFIG_KEVENT_SIGNAL
> + struct kevent_storage st;
> + u32 kevent_signals;
> +#endif
> };
>
> static inline pid_t process_group(struct task_struct *tsk)
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 1c999f3..e5b5b14 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -46,6 +46,7 @@
> #include <linux/delayacct.h>
> #include <linux/taskstats_kern.h>
> #include <linux/random.h>
> +#include <linux/kevent.h>
>
> #include <asm/pgtable.h>
> #include <asm/pgalloc.h>
> @@ -115,6 +116,9 @@ void __put_task_struct(struct task_struct *tsk)
> WARN_ON(atomic_read(&tsk->usage));
> WARN_ON(tsk == current);
>
> +#ifdef CONFIG_KEVENT_SIGNAL
> + kevent_storage_fini(&tsk->st);
> +#endif
> security_task_free(tsk);
> free_uid(tsk->user);
> put_group_info(tsk->group_info);
> @@ -1121,6 +1125,10 @@ static struct task_struct *copy_process(unsigned long clone_flags,
> if (retval)
> goto bad_fork_cleanup_namespace;
>
> +#ifdef CONFIG_KEVENT_SIGNAL
> + kevent_storage_init(p, &p->st);
> +#endif
> +
> p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
> /*
> * Clear TID on mm_release()?
> diff --git a/kernel/kevent/kevent_signal.c b/kernel/kevent/kevent_signal.c
> new file mode 100644
> index 0000000..0edd2e4
> --- /dev/null
> +++ b/kernel/kevent/kevent_signal.c
> @@ -0,0 +1,92 @@
> +/*
> + * kevent_signal.c
> + *
> + * 2006 Copyright (c) Evgeniy Polyakov <johnpol@....mipt.ru>
> + * All rights reserved.
> + *
> + * 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.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program; if not, write to the Free Software
> + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/types.h>
> +#include <linux/slab.h>
> +#include <linux/spinlock.h>
> +#include <linux/file.h>
> +#include <linux/fs.h>
> +#include <linux/kevent.h>
> +
> +static int kevent_signal_callback(struct kevent *k)
> +{
> + struct task_struct *tsk = k->st->origin;
> + int sig = k->event.id.raw[0];
> + int ret = 0;
> +
> + if (sig == tsk->kevent_signals)
> + ret = 1;
> +
> + if (ret && (k->event.id.raw_u64 & KEVENT_SIGNAL_NOMASK))
> + tsk->kevent_signals |= 0x80000000;
> +
> + return ret;
> +}
> +
> +int kevent_signal_enqueue(struct kevent *k)
> +{
> + int err;
> +
> + err = kevent_storage_enqueue(¤t->st, k);
> + if (err)
> + goto err_out_exit;
> +
> + if (k->event.req_flags & KEVENT_REQ_ALWAYS_QUEUE) {
> + kevent_requeue(k);
> + err = 0;
> + } else {
> + err = k->callbacks.callback(k);
> + if (err)
> + goto err_out_dequeue;
> + }
> +
> + return err;
> +
> +err_out_dequeue:
> + kevent_storage_dequeue(k->st, k);
> +err_out_exit:
> + return err;
> +}
> +
> +int kevent_signal_dequeue(struct kevent *k)
> +{
> + kevent_storage_dequeue(k->st, k);
> + return 0;
> +}
> +
> +int kevent_signal_notify(struct task_struct *tsk, int sig)
> +{
> + tsk->kevent_signals = sig;
> + kevent_storage_ready(&tsk->st, NULL, KEVENT_SIGNAL_DELIVERY);
> + return (tsk->kevent_signals & 0x80000000);
> +}
> +
> +static int __init kevent_init_signal(void)
> +{
> + struct kevent_callbacks sc = {
> + .callback = &kevent_signal_callback,
> + .enqueue = &kevent_signal_enqueue,
> + .dequeue = &kevent_signal_dequeue};
> +
> + return kevent_add_callbacks(&sc, KEVENT_SIGNAL);
> +}
> +module_init(kevent_init_signal);
> diff --git a/kernel/signal.c b/kernel/signal.c
> index fb5da6d..d3d3594 100644
> --- a/kernel/signal.c
> +++ b/kernel/signal.c
> @@ -23,6 +23,7 @@
> #include <linux/ptrace.h>
> #include <linux/signal.h>
> #include <linux/capability.h>
> +#include <linux/kevent.h>
> #include <asm/param.h>
> #include <asm/uaccess.h>
> #include <asm/unistd.h>
> @@ -703,6 +704,9 @@ static int send_signal(int sig, struct siginfo *info, struct task_struct *t,
> {
> struct sigqueue * q = NULL;
> int ret = 0;
> +
> + if (kevent_signal_notify(t, sig))
> + return 1;
>
> /*
> * fast-pathed signals for kernel-internal things like SIGSTOP
> @@ -782,6 +786,17 @@ specific_send_sig_info(int sig, struct siginfo *info, struct task_struct *t)
> ret = send_signal(sig, info, t, &t->pending);
> if (!ret && !sigismember(&t->blocked, sig))
> signal_wake_up(t, sig == SIGKILL);
> +#ifdef CONFIG_KEVENT_SIGNAL
> + /*
> + * Kevent allows to deliver signals through kevent queue,
> + * it is possible to setup kevent to not deliver
> + * signal through the usual way, in that case send_signal()
> + * returns 1 and signal is delivered only through kevent queue.
> + * We simulate successfull delivery notification through this hack:
> + */
> + if (ret == 1)
> + ret = 0;
> +#endif
> out:
> return ret;
> }
> @@ -971,6 +986,17 @@ __group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p)
> * to avoid several races.
> */
> ret = send_signal(sig, info, p, &p->signal->shared_pending);
> +#ifdef CONFIG_KEVENT_SIGNAL
> + /*
> + * Kevent allows to deliver signals through kevent queue,
> + * it is possible to setup kevent to not deliver
> + * signal through the usual way, in that case send_signal()
> + * returns 1 and signal is delivered only through kevent queue.
> + * We simulate successfull delivery notification through this hack:
> + */
> + if (ret == 1)
> + ret = 0;
> +#endif
> if (unlikely(ret))
> return ret;
>
>
> -
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