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SubjectRe: [patch 1/2] fork_connector: add a fork connector
From
Date
ChangeLog:

- Remove the global cn_fork_lock and replace it by a per CPU
counter.
- The processor ID has been added in the data part of the message.
Thus datas sent in a message are: "CPU_ID PARENT_PID CHILD_PID"

Those modifications were done to be more scalable because, as
mentioned by Jesse Barnes, the global cn_fork_lock won't work well on a
large CPU system.

This patch applies to 2.6.11-mm4.

Regards,
Guillaume

---
drivers/connector/Kconfig | 11 +++++
drivers/connector/Makefile | 1
drivers/connector/cn_fork.c | 85 ++++++++++++++++++++++++++++++++++++++++++++
include/linux/connector.h | 4 ++
kernel/fork.c | 44 ++++++++++++++++++++++
5 files changed, 145 insertions(+)

Index: linux-2.6.11-mm4-cnfork/drivers/connector/Kconfig
===================================================================
--- linux-2.6.11-mm4-cnfork.orig/drivers/connector/Kconfig 2005-03-16 14:21:46.000000000 +0100
+++ linux-2.6.11-mm4-cnfork/drivers/connector/Kconfig 2005-03-16 14:34:41.000000000 +0100
@@ -10,4 +10,15 @@
Connector support can also be built as a module. If so, the module
will be called cn.ko.

+config FORK_CONNECTOR
+ bool "Enable fork connector"
+ depends on CONNECTOR=y
+ default y
+ ---help---
+ It adds a connector in kernel/fork.c:do_fork() function. When a fork
+ occurs, netlink is used to transfer information about the parent and
+ its child. This information can be used by a user space application.
+ The fork connector can be enable/disable by sending a message to the
+ connector with the corresponding group id.
+
endmenu
Index: linux-2.6.11-mm4-cnfork/drivers/connector/Makefile
===================================================================
--- linux-2.6.11-mm4-cnfork.orig/drivers/connector/Makefile 2005-03-16 14:21:46.000000000 +0100
+++ linux-2.6.11-mm4-cnfork/drivers/connector/Makefile 2005-03-16 14:34:41.000000000 +0100
@@ -1,2 +1,3 @@
obj-$(CONFIG_CONNECTOR) += cn.o
+obj-$(CONFIG_FORK_CONNECTOR) += cn_fork.o
cn-objs := cn_queue.o connector.o
Index: linux-2.6.11-mm4-cnfork/drivers/connector/cn_fork.c
===================================================================
--- linux-2.6.11-mm4-cnfork.orig/drivers/connector/cn_fork.c 2003-01-30 11:24:37.000000000 +0100
+++ linux-2.6.11-mm4-cnfork/drivers/connector/cn_fork.c 2005-03-16 14:34:41.000000000 +0100
@@ -0,0 +1,85 @@
+/*
+ * cn_fork.c
+ *
+ * 2005 Copyright (c) Guillaume Thouvenin <guillaume.thouvenin@bull.net>
+ * 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/module.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+
+#include <linux/connector.h>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Guillaume Thouvenin <guillaume.thouvenin@bull.net>");
+MODULE_DESCRIPTION("Enable or disable the usage of the fork connector");
+
+int cn_fork_enable = 0;
+struct cb_id cb_fork_id = { CN_IDX_FORK, CN_VAL_FORK };
+
+/**
+ * cn_fork_callback - enable or disable the fork connector
+ * @data: message send by the connector
+ *
+ * The callback allows to enable or disable the sending of information
+ * about fork in the do_fork() routine. To enable the fork, the user
+ * space application must send the integer 1 in the data part of the
+ * message. To disable the fork connector, it must send the integer 0.
+ */
+static void cn_fork_callback(void *data)
+{
+ struct cn_msg *msg = (struct cn_msg *)data;
+
+ if (cn_already_initialized && (msg->len == sizeof(cn_fork_enable)))
+ memcpy(&cn_fork_enable, msg->data, sizeof(cn_fork_enable));
+}
+
+/**
+ * cn_fork_init - initialization entry point
+ *
+ * This routine will be run at kernel boot time because this driver is
+ * built in the kernel. It adds the connector callback to the connector
+ * driver.
+ */
+static int cn_fork_init(void)
+{
+ int err;
+
+ err = cn_add_callback(&cb_fork_id, "cn_fork", &cn_fork_callback);
+ if (err) {
+ printk(KERN_WARNING "Failed to register cn_fork\n");
+ return -EINVAL;
+ }
+
+ printk(KERN_NOTICE "cn_fork is registered\n");
+ return 0;
+}
+
+/**
+ * cn_fork_exit - exit entry point
+ *
+ * As this driver is always statically compiled into the kernel the
+ * cn_fork_exit has no effect.
+ */
+static void cn_fork_exit(void)
+{
+ cn_del_callback(&cb_fork_id);
+}
+
+module_init(cn_fork_init);
+module_exit(cn_fork_exit);
Index: linux-2.6.11-mm4-cnfork/include/linux/connector.h
===================================================================
--- linux-2.6.11-mm4-cnfork.orig/include/linux/connector.h 2005-03-16 14:21:49.000000000 +0100
+++ linux-2.6.11-mm4-cnfork/include/linux/connector.h 2005-03-16 14:34:41.000000000 +0100
@@ -28,6 +28,8 @@
#define CN_VAL_KOBJECT_UEVENT 0x0000
#define CN_IDX_SUPERIO 0xaabb /* SuperIO subsystem */
#define CN_VAL_SUPERIO 0xccdd
+#define CN_IDX_FORK 0xfeed /* fork events */
+#define CN_VAL_FORK 0xbeef


#define CONNECTOR_MAX_MSG_SIZE 1024
@@ -133,6 +135,8 @@
};

extern int cn_already_initialized;
+extern int cn_fork_enable;
+extern struct cb_id cb_fork_id;

int cn_add_callback(struct cb_id *, char *, void (* callback)(void *));
void cn_del_callback(struct cb_id *);
Index: linux-2.6.11-mm4-cnfork/kernel/fork.c
===================================================================
--- linux-2.6.11-mm4-cnfork.orig/kernel/fork.c 2005-03-16 14:21:49.000000000 +0100
+++ linux-2.6.11-mm4-cnfork/kernel/fork.c 2005-03-21 13:13:25.000000000 +0100
@@ -41,6 +41,7 @@
#include <linux/profile.h>
#include <linux/rmap.h>
#include <linux/acct.h>
+#include <linux/connector.h>

#include <asm/pgtable.h>
#include <asm/pgalloc.h>
@@ -63,6 +64,47 @@

EXPORT_SYMBOL(tasklist_lock);

+#ifdef CONFIG_FORK_CONNECTOR
+
+#define CN_FORK_INFO_SIZE 64
+#define CN_FORK_MSG_SIZE (sizeof(struct cn_msg) + CN_FORK_INFO_SIZE)
+
+static DEFINE_PER_CPU(unsigned long, fork_counts);
+
+static inline void fork_connector(pid_t parent, pid_t child)
+{
+ if (cn_fork_enable) {
+ struct cn_msg *msg;
+ __u8 buffer[CN_FORK_MSG_SIZE];
+
+ msg = (struct cn_msg *)buffer;
+
+ memcpy(&msg->id, &cb_fork_id, sizeof(msg->id));
+
+ msg->ack = 0; /* not used */
+ msg->seq = get_cpu_var(fork_counts)++;
+
+ /*
+ * size of data is the number of characters
+ * printed plus one for the trailing '\0'
+ */
+ memset(msg->data, '\0', CN_FORK_INFO_SIZE);
+ msg->len = scnprintf(msg->data, CN_FORK_INFO_SIZE-1,
+ "%i %i %i",
+ smp_processor_id(), parent, child) + 1;
+
+ put_cpu_var(fork_counts);
+
+ cn_netlink_send(msg, CN_IDX_FORK);
+ }
+}
+#else
+static inline void fork_connector(pid_t parent, pid_t child)
+{
+ return;
+}
+#endif /* CONFIG_FORK_CONNECTOR */
+
int nr_processes(void)
{
int cpu;
@@ -1253,6 +1295,8 @@
if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE))
ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP);
}
+
+ fork_connector(current->pid, p->pid);
} else {
free_pidmap(pid);
pid = PTR_ERR(p);

-
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