backport kernel changeset 831441862956fffa17b9801db37e6ea1650b0f69

From: Mauro Carvalho Chehab <mchehab@infradead.org>


kernel-sync:

Original patch description from the patch by Rafael J. Wysocki <rjw@sisk.pl>:

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.


Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/linux/drivers/media/video/msp3400-kthreads.c b/linux/drivers/media/video/msp3400-kthreads.c
index 041ad89c6..d10f683d9 100644
--- a/linux/drivers/media/video/msp3400-kthreads.c
+++ b/linux/drivers/media/video/msp3400-kthreads.c
@@ -23,6 +23,7 @@
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/i2c.h>
+#include <linux/freezer.h>
 #include <linux/videodev.h>
 #include <linux/videodev2.h>
 #include <media/v4l2-common.h>
@@ -477,6 +478,7 @@ int msp3400c_thread(void *data)
 #endif
 
 	v4l_dbg(1, msp_debug, client, "msp3400 daemon started\n");
+	set_freezable();
 	for (;;) {
 		v4l_dbg(2, msp_debug, client, "msp3400 thread: sleep\n");
 		msp_sleep(state, -1);
@@ -668,7 +670,7 @@ int msp3410d_thread(void *data)
 	msp_setup_thread(state);
 #endif
 	v4l_dbg(1, msp_debug, client, "msp3410 daemon started\n");
-
+	set_freezable();
 	for (;;) {
 		v4l_dbg(2, msp_debug, client, "msp3410 thread: sleep\n");
 		msp_sleep(state,-1);
@@ -975,7 +977,7 @@ int msp34xxg_thread(void *data)
 	msp_setup_thread(state);
 #endif
 	v4l_dbg(1, msp_debug, client, "msp34xxg daemon started\n");
-
+	set_freezable();
 	for (;;) {
 		v4l_dbg(2, msp_debug, client, "msp34xxg thread: sleep\n");
 		msp_sleep(state, -1);