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

From: Rafael J. Wysocki
Date: Mon Feb 26 2007 - 05:53:00 EST


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@xxxxxxx>

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@xxxxxxx>
---
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);
-
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