linux/init/do_mounts_initrd.c
Rafael J. Wysocki 8314418629 Freezer: make kernel threads nonfreezable by default
Currently, the freezer treats all tasks as freezable, except for the kernel
threads that explicitly set the PF_NOFREEZE flag for themselves.  This
approach is problematic, since it requires every kernel thread to either
set PF_NOFREEZE explicitly, or call try_to_freeze(), even if it doesn't
care for the freezing of tasks at all.

It seems better to only require the kernel threads that want to or need to
be frozen to use some freezer-related code and to remove any
freezer-related code from the other (nonfreezable) kernel threads, which is
done in this patch.

The patch causes all kernel threads to be nonfreezable by default (ie.  to
have PF_NOFREEZE set by default) and introduces the set_freezable()
function that should be called by the freezable kernel threads in order to
unset PF_NOFREEZE.  It also makes all of the currently freezable kernel
threads call set_freezable(), so it shouldn't cause any (intentional)
change of behaviour to appear.  Additionally, it updates documentation to
describe the freezing of tasks more accurately.

[akpm@linux-foundation.org: build fixes]
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Nigel Cunningham <nigel@nigel.suspend2.net>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-07-17 10:23:02 -07:00

121 lines
3 KiB
C

#include <linux/unistd.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/minix_fs.h>
#include <linux/ext2_fs.h>
#include <linux/romfs_fs.h>
#include <linux/initrd.h>
#include <linux/sched.h>
#include <linux/freezer.h>
#include "do_mounts.h"
unsigned long initrd_start, initrd_end;
int initrd_below_start_ok;
unsigned int real_root_dev; /* do_proc_dointvec cannot handle kdev_t */
static int __initdata old_fd, root_fd;
static int __initdata mount_initrd = 1;
static int __init no_initrd(char *str)
{
mount_initrd = 0;
return 1;
}
__setup("noinitrd", no_initrd);
static int __init do_linuxrc(void * shell)
{
static char *argv[] = { "linuxrc", NULL, };
extern char * envp_init[];
sys_close(old_fd);sys_close(root_fd);
sys_close(0);sys_close(1);sys_close(2);
sys_setsid();
(void) sys_open("/dev/console",O_RDWR,0);
(void) sys_dup(0);
(void) sys_dup(0);
return kernel_execve(shell, argv, envp_init);
}
static void __init handle_initrd(void)
{
int error;
int pid;
real_root_dev = new_encode_dev(ROOT_DEV);
create_dev("/dev/root.old", Root_RAM0);
/* mount initrd on rootfs' /root */
mount_block_root("/dev/root.old", root_mountflags & ~MS_RDONLY);
sys_mkdir("/old", 0700);
root_fd = sys_open("/", 0, 0);
old_fd = sys_open("/old", 0, 0);
/* move initrd over / and chdir/chroot in initrd root */
sys_chdir("/root");
sys_mount(".", "/", NULL, MS_MOVE, NULL);
sys_chroot(".");
pid = kernel_thread(do_linuxrc, "/linuxrc", SIGCHLD);
if (pid > 0)
while (pid != sys_wait4(-1, NULL, 0, NULL))
yield();
/* move initrd to rootfs' /old */
sys_fchdir(old_fd);
sys_mount("/", ".", NULL, MS_MOVE, NULL);
/* switch root and cwd back to / of rootfs */
sys_fchdir(root_fd);
sys_chroot(".");
sys_close(old_fd);
sys_close(root_fd);
if (new_decode_dev(real_root_dev) == Root_RAM0) {
sys_chdir("/old");
return;
}
ROOT_DEV = new_decode_dev(real_root_dev);
mount_root();
printk(KERN_NOTICE "Trying to move old root to /initrd ... ");
error = sys_mount("/old", "/root/initrd", NULL, MS_MOVE, NULL);
if (!error)
printk("okay\n");
else {
int fd = sys_open("/dev/root.old", O_RDWR, 0);
if (error == -ENOENT)
printk("/initrd does not exist. Ignored.\n");
else
printk("failed\n");
printk(KERN_NOTICE "Unmounting old root\n");
sys_umount("/old", MNT_DETACH);
printk(KERN_NOTICE "Trying to free ramdisk memory ... ");
if (fd < 0) {
error = fd;
} else {
error = sys_ioctl(fd, BLKFLSBUF, 0);
sys_close(fd);
}
printk(!error ? "okay\n" : "failed\n");
}
}
int __init initrd_load(void)
{
if (mount_initrd) {
create_dev("/dev/ram", Root_RAM0);
/*
* Load the initrd data into /dev/ram0. Execute it as initrd
* unless /dev/ram0 is supposed to be our actual root device,
* in that case the ram disk is just set up here, and gets
* mounted in the normal path.
*/
if (rd_load_image("/initrd.image") && ROOT_DEV != Root_RAM0) {
sys_unlink("/initrd.image");
handle_initrd();
return 1;
}
}
sys_unlink("/initrd.image");
return 0;
}