This is a note to let you know that I've just added the patch titled
[media] Revert "[media] videobuf_vm_{open,close} race fixes"
to the 3.12-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
revert-videobuf_vm_-open-close-race-fixes.patch
and it can be found in the queue-3.12 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From cca36e2eecec2b8fc869a50ffd3bd0adeed92b8b Mon Sep 17 00:00:00 2001
From: Hans Verkuil <hverkuil@xxxxxxxxx>
Date: Fri, 3 Jan 2014 08:10:49 -0300
Subject: [media] Revert "[media] videobuf_vm_{open,close} race fixes"
From: Hans Verkuil <hverkuil@xxxxxxxxx>
commit cca36e2eecec2b8fc869a50ffd3bd0adeed92b8b upstream.
This reverts commit a242f426108c284049a69710f871cc9f11b13e61.
That commit actually caused deadlocks, rather then fixing them.
If ext_lock is set to NULL (otherwise videobuf_queue_lock doesn't do
anything), then you get this deadlock:
The driver's mmap function calls videobuf_mmap_mapper which calls
videobuf_queue_lock on q. videobuf_mmap_mapper calls __videobuf_mmap_mapper,
__videobuf_mmap_mapper calls videobuf_vm_open and videobuf_vm_open
calls videobuf_queue_lock on q (introduced by above patch): deadlocked.
This affects drivers using dma-contig and dma-vmalloc. Only dma-sg is
not affected since it doesn't call videobuf_vm_open from __videobuf_mmap_mapper.
Most drivers these days have a non-NULL ext_lock. Those that still use
NULL there are all fairly obscure drivers, which is why this hasn't been
seen earlier.
Since everything worked perfectly fine for many years I prefer to just
revert this patch rather than trying to fix it. videobuf is quite fragile
and I rather not touch it too much. Work is (slowly) progressing to move
everything over to vb2 or at the very least use non-NULL ext_lock in
videobuf.
Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Reported-by: Pete Eberlein <pete@xxxxxxxxxxxx>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/media/v4l2-core/videobuf-dma-contig.c | 12 +++++-------
drivers/media/v4l2-core/videobuf-dma-sg.c | 10 ++++------
drivers/media/v4l2-core/videobuf-vmalloc.c | 10 ++++------
3 files changed, 13 insertions(+), 19 deletions(-)
--- a/drivers/media/v4l2-core/videobuf-dma-contig.c
+++ b/drivers/media/v4l2-core/videobuf-dma-contig.c
@@ -66,14 +66,11 @@ static void __videobuf_dc_free(struct de
static void videobuf_vm_open(struct vm_area_struct *vma)
{
struct videobuf_mapping *map = vma->vm_private_data;
- struct videobuf_queue *q = map->q;
- dev_dbg(q->dev, "vm_open %p [count=%u,vma=%08lx-%08lx]\n",
+ dev_dbg(map->q->dev, "vm_open %p [count=%u,vma=%08lx-%08lx]\n",
map, map->count, vma->vm_start, vma->vm_end);
- videobuf_queue_lock(q);
map->count++;
- videobuf_queue_unlock(q);
}
static void videobuf_vm_close(struct vm_area_struct *vma)
@@ -85,11 +82,12 @@ static void videobuf_vm_close(struct vm_
dev_dbg(q->dev, "vm_close %p [count=%u,vma=%08lx-%08lx]\n",
map, map->count, vma->vm_start, vma->vm_end);
- videobuf_queue_lock(q);
- if (!--map->count) {
+ map->count--;
+ if (0 == map->count) {
struct videobuf_dma_contig_memory *mem;
dev_dbg(q->dev, "munmap %p q=%p\n", map, q);
+ videobuf_queue_lock(q);
/* We need first to cancel streams, before unmapping */
if (q->streaming)
@@ -128,8 +126,8 @@ static void videobuf_vm_close(struct vm_
kfree(map);
+ videobuf_queue_unlock(q);
}
- videobuf_queue_unlock(q);
}
static const struct vm_operations_struct videobuf_vm_ops = {
--- a/drivers/media/v4l2-core/videobuf-dma-sg.c
+++ b/drivers/media/v4l2-core/videobuf-dma-sg.c
@@ -338,14 +338,11 @@ EXPORT_SYMBOL_GPL(videobuf_dma_free);
static void videobuf_vm_open(struct vm_area_struct *vma)
{
struct videobuf_mapping *map = vma->vm_private_data;
- struct videobuf_queue *q = map->q;
dprintk(2, "vm_open %p [count=%d,vma=%08lx-%08lx]\n", map,
map->count, vma->vm_start, vma->vm_end);
- videobuf_queue_lock(q);
map->count++;
- videobuf_queue_unlock(q);
}
static void videobuf_vm_close(struct vm_area_struct *vma)
@@ -358,9 +355,10 @@ static void videobuf_vm_close(struct vm_
dprintk(2, "vm_close %p [count=%d,vma=%08lx-%08lx]\n", map,
map->count, vma->vm_start, vma->vm_end);
- videobuf_queue_lock(q);
- if (!--map->count) {
+ map->count--;
+ if (0 == map->count) {
dprintk(1, "munmap %p q=%p\n", map, q);
+ videobuf_queue_lock(q);
for (i = 0; i < VIDEO_MAX_FRAME; i++) {
if (NULL == q->bufs[i])
continue;
@@ -376,9 +374,9 @@ static void videobuf_vm_close(struct vm_
q->bufs[i]->baddr = 0;
q->ops->buf_release(q, q->bufs[i]);
}
+ videobuf_queue_unlock(q);
kfree(map);
}
- videobuf_queue_unlock(q);
return;
}
--- a/drivers/media/v4l2-core/videobuf-vmalloc.c
+++ b/drivers/media/v4l2-core/videobuf-vmalloc.c
@@ -54,14 +54,11 @@ MODULE_LICENSE("GPL");
static void videobuf_vm_open(struct vm_area_struct *vma)
{
struct videobuf_mapping *map = vma->vm_private_data;
- struct videobuf_queue *q = map->q;
dprintk(2, "vm_open %p [count=%u,vma=%08lx-%08lx]\n", map,
map->count, vma->vm_start, vma->vm_end);
- videobuf_queue_lock(q);
map->count++;
- videobuf_queue_unlock(q);
}
static void videobuf_vm_close(struct vm_area_struct *vma)
@@ -73,11 +70,12 @@ static void videobuf_vm_close(struct vm_
dprintk(2, "vm_close %p [count=%u,vma=%08lx-%08lx]\n", map,
map->count, vma->vm_start, vma->vm_end);
- videobuf_queue_lock(q);
- if (!--map->count) {
+ map->count--;
+ if (0 == map->count) {
struct videobuf_vmalloc_memory *mem;
dprintk(1, "munmap %p q=%p\n", map, q);
+ videobuf_queue_lock(q);
/* We need first to cancel streams, before unmapping */
if (q->streaming)
@@ -116,8 +114,8 @@ static void videobuf_vm_close(struct vm_
kfree(map);
+ videobuf_queue_unlock(q);
}
- videobuf_queue_unlock(q);
return;
}
Patches currently in stable-queue which might be from hverkuil@xxxxxxxxx are
queue-3.12/revert-videobuf_vm_-open-close-race-fixes.patch
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