This patch adds a fork connector in the do_fork() routine. It sends a netlink datagram when enabled. The message can be read by a user space application. By this way, the user space application is alerted when a fork occurs.
It uses the userspace <-> kernelspace connector that works on top of the netlink protocol. The fork connector is enabled or disabled by sending a message to the connector. This operation should be done by only one application. Such application can be downloaded from http://cvs.sourceforge.net/viewcvs.py/elsa/elsa_project/utils/fcctl.c The unique sequence number of messages can be used to check if a message is lost. This sequence number is relative to a CPU. The lmbench shows that the overhead (the construction and the sending of the message) in the fork() routine is around 7%. This patch applies to 2.6.12-rc1-mm3. Some other patches are needed that fix problems in the connector.c file. At least, you need to apply the patch provided in the second email. Signed-off-by: Guillaume Thouvenin <[EMAIL PROTECTED]> --- drivers/connector/Kconfig | 11 ++++ drivers/connector/Makefile | 1 drivers/connector/cn_fork.c | 104 ++++++++++++++++++++++++++++++++++++++++++++ include/linux/connector.h | 8 +++ kernel/fork.c | 44 ++++++++++++++++++ 5 files changed, 168 insertions(+) Index: linux-2.6.12-rc1-mm3-cnfork/drivers/connector/Kconfig =================================================================== --- linux-2.6.12-rc1-mm3-cnfork.orig/drivers/connector/Kconfig 2005-03-25 09:47:09.000000000 +0100 +++ linux-2.6.12-rc1-mm3-cnfork/drivers/connector/Kconfig 2005-03-25 10:14:21.000000000 +0100 @@ -10,4 +10,15 @@ config CONNECTOR 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-2.6.12-rc1-mm3-cnfork/drivers/connector/Makefile =================================================================== --- linux-2.6.12-rc1-mm3-cnfork.orig/drivers/connector/Makefile 2005-03-25 09:47:09.000000000 +0100 +++ linux-2.6.12-rc1-mm3-cnfork/drivers/connector/Makefile 2005-03-25 10:14:21.000000000 +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-2.6.12-rc1-mm3-cnfork/drivers/connector/cn_fork.c =================================================================== --- linux-2.6.12-rc1-mm3-cnfork.orig/drivers/connector/cn_fork.c 2003-01-30 11:24:37.000000000 +0100 +++ linux-2.6.12-rc1-mm3-cnfork/drivers/connector/cn_fork.c 2005-03-25 10:14:21.000000000 +0100 @@ -0,0 +1,104 @@ +/* + * cn_fork.c + * + * 2005 Copyright (c) Guillaume Thouvenin <[EMAIL PROTECTED]> + * 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 <[EMAIL PROTECTED]>"); +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 }; + +static inline void cn_fork_send_status(void) +{ + /* TODO */ + printk(KERN_INFO "cn_fork_enable == %d\n", cn_fork_enable); +} + +/** + * 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; + int action; + + if (cn_already_initialized && (msg->len == sizeof(cn_fork_enable))) { + memcpy(&action, msg->data, sizeof(cn_fork_enable)); + switch(action) { + case FORK_CN_START: + cn_fork_enable = 1; + break; + case FORK_CN_STOP: + cn_fork_enable = 0; + break; + case FORK_CN_STATUS: + cn_fork_send_status(); + break; + } + } +} + +/** + * 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-2.6.12-rc1-mm3-cnfork/include/linux/connector.h =================================================================== --- linux-2.6.12-rc1-mm3-cnfork.orig/include/linux/connector.h 2005-03-25 09:47:11.000000000 +0100 +++ linux-2.6.12-rc1-mm3-cnfork/include/linux/connector.h 2005-03-25 10:14:21.000000000 +0100 @@ -28,10 +28,16 @@ #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 +#define FORK_CN_STOP 0 +#define FORK_CN_START 1 +#define FORK_CN_STATUS 2 + struct cb_id { __u32 idx; @@ -133,6 +139,8 @@ struct cn_dev }; 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-2.6.12-rc1-mm3-cnfork/kernel/fork.c =================================================================== --- linux-2.6.12-rc1-mm3-cnfork.orig/kernel/fork.c 2005-03-25 09:47:11.000000000 +0100 +++ linux-2.6.12-rc1-mm3-cnfork/kernel/fork.c 2005-03-25 10:14:21.000000000 +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 @@ DEFINE_PER_CPU(unsigned long, process_co 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 @@ long do_fork(unsigned long clone_flags, 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); - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
