[RFC][PATCH 3/3] Freezer: Prevent ___call_usermodehelper from missing freezing requests

["Rafael J. Wysocki" <rjw@sisk.pl>]

NOTE: Alternatively, we can just drop flush_signals() from there, but I'm not
sure that's the right thing to do.

---
From: Rafael J. Wysocki <rjw@sisk.pl>

Since ____call_usermodehelper() calls flush_signals(current), the task that
enters it may miss a freezing request.  However, if ____call_usermodehelper()
clears TIF_FREEZE for the current task after flush_signals(current) returns, the
freezer will generate one more freezing request for this task.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
---
 kernel/kmod.c |    2 ++
 1 file changed, 2 insertions(+)

Index: linux-2.6.20-mm2/kernel/kmod.c
===================================================================
--- linux-2.6.20-mm2.orig/kernel/kmod.c	2007-02-25 12:07:15.000000000 +0100
+++ linux-2.6.20-mm2/kernel/kmod.c	2007-02-25 12:49:16.000000000 +0100
@@ -34,6 +34,7 @@
 #include <linux/kernel.h>
 #include <linux/init.h>
 #include <linux/resource.h>
+#include <linux/freezer.h>
 #include <asm/uaccess.h>
 
 extern int delete_module(const char *name, unsigned int flags);
@@ -258,6 +259,7 @@ static int ____call_usermodehelper(void 
 	new_session = key_get(sub_info->ring);
 	flush_signals(current);
 	spin_lock_irq(&current->sighand->siglock);
+	do_not_freeze(current);
 	old_session = __install_session_keyring(current, new_session);
 	flush_signal_handlers(current, 1);
 	sigemptyset(&current->blocked);