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Commit 2ca067ef authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
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poweroff: change orderly_poweroff() to use schedule_work() 



David said:

    Commit 6c0c0d4d ("poweroff: fix bug in orderly_poweroff()")
    apparently fixes one bug in orderly_poweroff(), but introduces
    another.  The comments on orderly_poweroff() claim it can be called
    from any context - and indeed we call it from interrupt context in
    arch/powerpc/platforms/pseries/ras.c for example.  But since that
    commit this is no longer safe, since call_usermodehelper_fns() is not
    safe in interrupt context without the UMH_NO_WAIT option.

orderly_poweroff() can be used from any context but UMH_WAIT_EXEC is
sleepable.  Move the "force" logic into __orderly_poweroff() and change
orderly_poweroff() to use the global poweroff_work which simply calls
__orderly_poweroff().

While at it, remove the unneeded "int argc" and change argv_split() to
use GFP_KERNEL.

We use the global "bool poweroff_force" to pass the argument, this can
obviously affect the previous request if it is pending/running.  So we
only allow the "false => true" transition assuming that the pending
"true" should succeed anyway.  If schedule_work() fails after that we
know that work->func() was not called yet, it must see the new value.

This means that orderly_poweroff() becomes async even if we do not run
the command and always succeeds, schedule_work() can only fail if the
work is already pending.  We can export __orderly_poweroff() and change
the non-atomic callers which want the old semantics.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Reported-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
Reported-by: default avatarDavid Gibson <david@gibson.dropbear.id.au>
Cc: Lucas De Marchi <lucas.demarchi@profusion.mobi>
Cc: Feng Hong <hongfeng@marvell.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Serge Hallyn <serge.hallyn@canonical.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent d0028588

kernel/sys.c

+32 −25
Original line number Original line Diff line number Diff line
@@ -2185,9 +2185,8 @@ SYSCALL_DEFINE3(getcpu, unsigned __user *, cpup, unsigned __user *, nodep, 




char poweroff_cmd[POWEROFF_CMD_PATH_LEN] = "/sbin/poweroff";

char poweroff_cmd[POWEROFF_CMD_PATH_LEN] = "/sbin/poweroff";





static int __orderly_poweroff(void)

static int __orderly_poweroff(bool force)

{

{

	int argc;

	char **argv;

	char **argv;

	static char *envp[] = {

	static char *envp[] = {

		"HOME=/",

		"HOME=/",
@@ -2196,35 +2195,19 @@ static int __orderly_poweroff(void) 
	};

	};

	int ret;

	int ret;





	argv = argv_split(GFP_ATOMIC, poweroff_cmd, &argc);

	argv = argv_split(GFP_KERNEL, poweroff_cmd, NULL);

	if (argv == NULL) {

	if (argv) {

		ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);

		argv_free(argv);

	} else {

		printk(KERN_WARNING "%s failed to allocate memory for \"%s\"\n",

		printk(KERN_WARNING "%s failed to allocate memory for \"%s\"\n",

					 __func__, poweroff_cmd);

					 __func__, poweroff_cmd);

		return -ENOMEM;

		ret = -ENOMEM;

	}

	}





	ret = call_usermodehelper_fns(argv[0], argv, envp, UMH_WAIT_EXEC,

				      NULL, NULL, NULL);

	argv_free(argv);



	return ret;

}



/**

 * orderly_poweroff - Trigger an orderly system poweroff

 * @force: force poweroff if command execution fails

 *

 * This may be called from any context to trigger a system shutdown.

 * If the orderly shutdown fails, it will force an immediate shutdown.

 */

int orderly_poweroff(bool force)

{

	int ret = __orderly_poweroff();



	if (ret && force) {

	if (ret && force) {

		printk(KERN_WARNING "Failed to start orderly shutdown: "

		printk(KERN_WARNING "Failed to start orderly shutdown: "

					"forcing the issue\n");

					"forcing the issue\n");



		/*

		/*

		 * I guess this should try to kick off some daemon to sync and

		 * I guess this should try to kick off some daemon to sync and

		 * poweroff asap.  Or not even bother syncing if we're doing an

		 * poweroff asap.  Or not even bother syncing if we're doing an
@@ -2236,4 +2219,28 @@ int orderly_poweroff(bool force) 




	return ret;

	return ret;

}

}



static bool poweroff_force;



static void poweroff_work_func(struct work_struct *work)

{

	__orderly_poweroff(poweroff_force);

}



static DECLARE_WORK(poweroff_work, poweroff_work_func);



/**

 * orderly_poweroff - Trigger an orderly system poweroff

 * @force: force poweroff if command execution fails

 *

 * This may be called from any context to trigger a system shutdown.

 * If the orderly shutdown fails, it will force an immediate shutdown.

 */

int orderly_poweroff(bool force)

{

	if (force) /* do not override the pending "true" */

		poweroff_force = true;

	schedule_work(&poweroff_work);

	return 0;

}

EXPORT_SYMBOL_GPL(orderly_poweroff);
 
EXPORT_SYMBOL_GPL(orderly_poweroff);