From: Jan Kara <jack@suse.cz>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Hans Verkuil <hverkuil@xs4all.nl>,
linux-media@vger.kernel.org,
Mauro Carvalho Chehab <mchehab@osg.samsung.com>,
linux-samsung-soc@vger.kernel.org, linux-mm@kvack.org,
Jan Kara <jack@suse.cz>
Subject: [PATCH 1/10] [media] vb2: Push mmap_sem down to memops
Date: Thu, 18 Jun 2015 16:08:31 +0200 [thread overview]
Message-ID: <1434636520-25116-2-git-send-email-jack@suse.cz> (raw)
In-Reply-To: <1434636520-25116-1-git-send-email-jack@suse.cz>
Currently vb2 core acquires mmap_sem just around call to
__qbuf_userptr(). However since commit f035eb4e976ef5 (videobuf2: fix
lockdep warning) it isn't necessary to acquire it so early as we no
longer have to drop queue mutex before acquiring mmap_sem. So push
acquisition of mmap_sem down into .get_userptr memop so that the
semaphore is acquired for a shorter time and it is clearer what it is
needed for.
Note that we also need mmap_sem in .put_userptr memop since that ends up
calling vb2_put_vma() which calls vma->vm_ops->close() which should be
called with mmap_sem held. However we didn't hold mmap_sem in some code
paths anyway (e.g. when called via vb2_ioctl_reqbufs() ->
__vb2_queue_free() -> vb2_dma_sg_put_userptr()) and getting mmap_sem in
put_userptr() introduces a lock inversion with queue->mmap_lock in the
above mentioned call path.
Luckily this whole locking mess will get resolved once we convert
videobuf2 core to the new mm helper which avoids the need for mmap_sem
in .put_userptr memop altogether.
Signed-off-by: Jan Kara <jack@suse.cz>
---
drivers/media/v4l2-core/videobuf2-core.c | 2 --
drivers/media/v4l2-core/videobuf2-dma-contig.c | 5 +++++
drivers/media/v4l2-core/videobuf2-dma-sg.c | 4 ++++
drivers/media/v4l2-core/videobuf2-vmalloc.c | 4 +++-
4 files changed, 12 insertions(+), 3 deletions(-)
diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
index 66ada01c796c..20cdbc0900ea 100644
--- a/drivers/media/v4l2-core/videobuf2-core.c
+++ b/drivers/media/v4l2-core/videobuf2-core.c
@@ -1657,9 +1657,7 @@ static int __buf_prepare(struct vb2_buffer *vb, const struct v4l2_buffer *b)
ret = __qbuf_mmap(vb, b);
break;
case V4L2_MEMORY_USERPTR:
- down_read(¤t->mm->mmap_sem);
ret = __qbuf_userptr(vb, b);
- up_read(¤t->mm->mmap_sem);
break;
case V4L2_MEMORY_DMABUF:
ret = __qbuf_dmabuf(vb, b);
diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c b/drivers/media/v4l2-core/videobuf2-dma-contig.c
index 644dec73d220..8e660f033d3c 100644
--- a/drivers/media/v4l2-core/videobuf2-dma-contig.c
+++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c
@@ -616,6 +616,7 @@ static void *vb2_dc_get_userptr(void *alloc_ctx, unsigned long vaddr,
goto fail_buf;
}
+ down_read(¤t->mm->mmap_sem);
/* current->mm->mmap_sem is taken by videobuf2 core */
vma = find_vma(current->mm, vaddr);
if (!vma) {
@@ -642,6 +643,7 @@ static void *vb2_dc_get_userptr(void *alloc_ctx, unsigned long vaddr,
if (ret) {
unsigned long pfn;
if (vb2_dc_get_user_pfn(start, n_pages, vma, &pfn) == 0) {
+ up_read(¤t->mm->mmap_sem);
buf->dma_addr = vb2_dc_pfn_to_dma(buf->dev, pfn);
buf->size = size;
kfree(pages);
@@ -651,6 +653,7 @@ static void *vb2_dc_get_userptr(void *alloc_ctx, unsigned long vaddr,
pr_err("failed to get user pages\n");
goto fail_vma;
}
+ up_read(¤t->mm->mmap_sem);
sgt = kzalloc(sizeof(*sgt), GFP_KERNEL);
if (!sgt) {
@@ -713,10 +716,12 @@ fail_get_user_pages:
while (n_pages)
put_page(pages[--n_pages]);
+ down_read(¤t->mm->mmap_sem);
fail_vma:
vb2_put_vma(buf->vma);
fail_pages:
+ up_read(¤t->mm->mmap_sem);
kfree(pages); /* kfree is NULL-proof */
fail_buf:
diff --git a/drivers/media/v4l2-core/videobuf2-dma-sg.c b/drivers/media/v4l2-core/videobuf2-dma-sg.c
index 45c708e463b9..cdcf5ad79012 100644
--- a/drivers/media/v4l2-core/videobuf2-dma-sg.c
+++ b/drivers/media/v4l2-core/videobuf2-dma-sg.c
@@ -263,6 +263,7 @@ static void *vb2_dma_sg_get_userptr(void *alloc_ctx, unsigned long vaddr,
if (!buf->pages)
goto userptr_fail_alloc_pages;
+ down_read(¤t->mm->mmap_sem);
vma = find_vma(current->mm, vaddr);
if (!vma) {
dprintk(1, "no vma for address %lu\n", vaddr);
@@ -301,6 +302,7 @@ static void *vb2_dma_sg_get_userptr(void *alloc_ctx, unsigned long vaddr,
1, /* force */
buf->pages,
NULL);
+ up_read(¤t->mm->mmap_sem);
if (num_pages_from_user != buf->num_pages)
goto userptr_fail_get_user_pages;
@@ -328,8 +330,10 @@ userptr_fail_get_user_pages:
if (!vma_is_io(buf->vma))
while (--num_pages_from_user >= 0)
put_page(buf->pages[num_pages_from_user]);
+ down_read(¤t->mm->mmap_sem);
vb2_put_vma(buf->vma);
userptr_fail_find_vma:
+ up_read(¤t->mm->mmap_sem);
kfree(buf->pages);
userptr_fail_alloc_pages:
kfree(buf);
diff --git a/drivers/media/v4l2-core/videobuf2-vmalloc.c b/drivers/media/v4l2-core/videobuf2-vmalloc.c
index 657ab302a5cf..3199c379cd47 100644
--- a/drivers/media/v4l2-core/videobuf2-vmalloc.c
+++ b/drivers/media/v4l2-core/videobuf2-vmalloc.c
@@ -89,7 +89,7 @@ static void *vb2_vmalloc_get_userptr(void *alloc_ctx, unsigned long vaddr,
offset = vaddr & ~PAGE_MASK;
buf->size = size;
-
+ down_read(¤t->mm->mmap_sem);
vma = find_vma(current->mm, vaddr);
if (vma && (vma->vm_flags & VM_PFNMAP) && (vma->vm_pgoff)) {
if (vb2_get_contig_userptr(vaddr, size, &vma, &physp))
@@ -121,6 +121,7 @@ static void *vb2_vmalloc_get_userptr(void *alloc_ctx, unsigned long vaddr,
if (!buf->vaddr)
goto fail_get_user_pages;
}
+ up_read(¤t->mm->mmap_sem);
buf->vaddr += offset;
return buf;
@@ -133,6 +134,7 @@ fail_get_user_pages:
kfree(buf->pages);
fail_pages_array_alloc:
+ up_read(¤t->mm->mmap_sem);
kfree(buf);
return NULL;
--
2.1.4
--
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WARNING: multiple messages have this Message-ID (diff)
From: Jan Kara <jack@suse.cz>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Hans Verkuil <hverkuil@xs4all.nl>,
linux-media@vger.kernel.org,
Mauro Carvalho Chehab <mchehab@osg.samsung.com>,
linux-samsung-soc@vger.kernel.org, linux-mm@kvack.org,
Jan Kara <jack@suse.cz>
Subject: [PATCH 1/10] [media] vb2: Push mmap_sem down to memops
Date: Thu, 18 Jun 2015 16:08:31 +0200 [thread overview]
Message-ID: <1434636520-25116-2-git-send-email-jack@suse.cz> (raw)
In-Reply-To: <1434636520-25116-1-git-send-email-jack@suse.cz>
Currently vb2 core acquires mmap_sem just around call to
__qbuf_userptr(). However since commit f035eb4e976ef5 (videobuf2: fix
lockdep warning) it isn't necessary to acquire it so early as we no
longer have to drop queue mutex before acquiring mmap_sem. So push
acquisition of mmap_sem down into .get_userptr memop so that the
semaphore is acquired for a shorter time and it is clearer what it is
needed for.
Note that we also need mmap_sem in .put_userptr memop since that ends up
calling vb2_put_vma() which calls vma->vm_ops->close() which should be
called with mmap_sem held. However we didn't hold mmap_sem in some code
paths anyway (e.g. when called via vb2_ioctl_reqbufs() ->
__vb2_queue_free() -> vb2_dma_sg_put_userptr()) and getting mmap_sem in
put_userptr() introduces a lock inversion with queue->mmap_lock in the
above mentioned call path.
Luckily this whole locking mess will get resolved once we convert
videobuf2 core to the new mm helper which avoids the need for mmap_sem
in .put_userptr memop altogether.
Signed-off-by: Jan Kara <jack@suse.cz>
---
drivers/media/v4l2-core/videobuf2-core.c | 2 --
drivers/media/v4l2-core/videobuf2-dma-contig.c | 5 +++++
drivers/media/v4l2-core/videobuf2-dma-sg.c | 4 ++++
drivers/media/v4l2-core/videobuf2-vmalloc.c | 4 +++-
4 files changed, 12 insertions(+), 3 deletions(-)
diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
index 66ada01c796c..20cdbc0900ea 100644
--- a/drivers/media/v4l2-core/videobuf2-core.c
+++ b/drivers/media/v4l2-core/videobuf2-core.c
@@ -1657,9 +1657,7 @@ static int __buf_prepare(struct vb2_buffer *vb, const struct v4l2_buffer *b)
ret = __qbuf_mmap(vb, b);
break;
case V4L2_MEMORY_USERPTR:
- down_read(¤t->mm->mmap_sem);
ret = __qbuf_userptr(vb, b);
- up_read(¤t->mm->mmap_sem);
break;
case V4L2_MEMORY_DMABUF:
ret = __qbuf_dmabuf(vb, b);
diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c b/drivers/media/v4l2-core/videobuf2-dma-contig.c
index 644dec73d220..8e660f033d3c 100644
--- a/drivers/media/v4l2-core/videobuf2-dma-contig.c
+++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c
@@ -616,6 +616,7 @@ static void *vb2_dc_get_userptr(void *alloc_ctx, unsigned long vaddr,
goto fail_buf;
}
+ down_read(¤t->mm->mmap_sem);
/* current->mm->mmap_sem is taken by videobuf2 core */
vma = find_vma(current->mm, vaddr);
if (!vma) {
@@ -642,6 +643,7 @@ static void *vb2_dc_get_userptr(void *alloc_ctx, unsigned long vaddr,
if (ret) {
unsigned long pfn;
if (vb2_dc_get_user_pfn(start, n_pages, vma, &pfn) == 0) {
+ up_read(¤t->mm->mmap_sem);
buf->dma_addr = vb2_dc_pfn_to_dma(buf->dev, pfn);
buf->size = size;
kfree(pages);
@@ -651,6 +653,7 @@ static void *vb2_dc_get_userptr(void *alloc_ctx, unsigned long vaddr,
pr_err("failed to get user pages\n");
goto fail_vma;
}
+ up_read(¤t->mm->mmap_sem);
sgt = kzalloc(sizeof(*sgt), GFP_KERNEL);
if (!sgt) {
@@ -713,10 +716,12 @@ fail_get_user_pages:
while (n_pages)
put_page(pages[--n_pages]);
+ down_read(¤t->mm->mmap_sem);
fail_vma:
vb2_put_vma(buf->vma);
fail_pages:
+ up_read(¤t->mm->mmap_sem);
kfree(pages); /* kfree is NULL-proof */
fail_buf:
diff --git a/drivers/media/v4l2-core/videobuf2-dma-sg.c b/drivers/media/v4l2-core/videobuf2-dma-sg.c
index 45c708e463b9..cdcf5ad79012 100644
--- a/drivers/media/v4l2-core/videobuf2-dma-sg.c
+++ b/drivers/media/v4l2-core/videobuf2-dma-sg.c
@@ -263,6 +263,7 @@ static void *vb2_dma_sg_get_userptr(void *alloc_ctx, unsigned long vaddr,
if (!buf->pages)
goto userptr_fail_alloc_pages;
+ down_read(¤t->mm->mmap_sem);
vma = find_vma(current->mm, vaddr);
if (!vma) {
dprintk(1, "no vma for address %lu\n", vaddr);
@@ -301,6 +302,7 @@ static void *vb2_dma_sg_get_userptr(void *alloc_ctx, unsigned long vaddr,
1, /* force */
buf->pages,
NULL);
+ up_read(¤t->mm->mmap_sem);
if (num_pages_from_user != buf->num_pages)
goto userptr_fail_get_user_pages;
@@ -328,8 +330,10 @@ userptr_fail_get_user_pages:
if (!vma_is_io(buf->vma))
while (--num_pages_from_user >= 0)
put_page(buf->pages[num_pages_from_user]);
+ down_read(¤t->mm->mmap_sem);
vb2_put_vma(buf->vma);
userptr_fail_find_vma:
+ up_read(¤t->mm->mmap_sem);
kfree(buf->pages);
userptr_fail_alloc_pages:
kfree(buf);
diff --git a/drivers/media/v4l2-core/videobuf2-vmalloc.c b/drivers/media/v4l2-core/videobuf2-vmalloc.c
index 657ab302a5cf..3199c379cd47 100644
--- a/drivers/media/v4l2-core/videobuf2-vmalloc.c
+++ b/drivers/media/v4l2-core/videobuf2-vmalloc.c
@@ -89,7 +89,7 @@ static void *vb2_vmalloc_get_userptr(void *alloc_ctx, unsigned long vaddr,
offset = vaddr & ~PAGE_MASK;
buf->size = size;
-
+ down_read(¤t->mm->mmap_sem);
vma = find_vma(current->mm, vaddr);
if (vma && (vma->vm_flags & VM_PFNMAP) && (vma->vm_pgoff)) {
if (vb2_get_contig_userptr(vaddr, size, &vma, &physp))
@@ -121,6 +121,7 @@ static void *vb2_vmalloc_get_userptr(void *alloc_ctx, unsigned long vaddr,
if (!buf->vaddr)
goto fail_get_user_pages;
}
+ up_read(¤t->mm->mmap_sem);
buf->vaddr += offset;
return buf;
@@ -133,6 +134,7 @@ fail_get_user_pages:
kfree(buf->pages);
fail_pages_array_alloc:
+ up_read(¤t->mm->mmap_sem);
kfree(buf);
return NULL;
--
2.1.4
next prev parent reply other threads:[~2015-06-18 14:08 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-18 14:08 [PATCH 0/10 v6] Helper to abstract vma handling in media layer Jan Kara
2015-06-18 14:08 ` Jan Kara
2015-06-18 14:08 ` Jan Kara [this message]
2015-06-18 14:08 ` [PATCH 1/10] [media] vb2: Push mmap_sem down to memops Jan Kara
2015-06-18 14:08 ` [PATCH 2/10] mm: Provide new get_vaddr_frames() helper Jan Kara
2015-06-18 14:08 ` Jan Kara
2015-06-18 14:08 ` [PATCH 3/10] media: omap_vout: Convert omap_vout_uservirt_to_phys() to use get_vaddr_pfns() Jan Kara
2015-06-18 14:08 ` Jan Kara
2015-06-18 14:08 ` [PATCH 4/10] vb2: Provide helpers for mapping virtual addresses Jan Kara
2015-06-18 14:08 ` Jan Kara
2015-06-18 14:08 ` [PATCH 5/10] media: vb2: Convert vb2_dma_sg_get_userptr() to use frame vector Jan Kara
2015-06-18 14:08 ` Jan Kara
2015-06-18 14:08 ` [PATCH 6/10] media: vb2: Convert vb2_vmalloc_get_userptr() " Jan Kara
2015-06-18 14:08 ` Jan Kara
2015-06-18 14:08 ` [PATCH 7/10] media: vb2: Convert vb2_dc_get_userptr() " Jan Kara
2015-06-18 14:08 ` Jan Kara
2015-06-18 14:08 ` [PATCH 8/10] media: vb2: Remove unused functions Jan Kara
2015-06-18 14:08 ` Jan Kara
2015-06-18 14:08 ` [PATCH 9/10] drm/exynos: Convert g2d_userptr_get_dma_addr() to use get_vaddr_frames() Jan Kara
2015-06-18 14:08 ` Jan Kara
2015-06-18 14:08 ` [PATCH 10/10] mm: Move get_vaddr_frames() behind a config option Jan Kara
2015-06-18 14:08 ` Jan Kara
2015-07-09 11:48 ` [PATCH 0/10 v6] Helper to abstract vma handling in media layer Jan Kara
2015-07-09 11:48 ` Jan Kara
2015-07-09 12:12 ` Hans Verkuil
2015-07-09 12:12 ` Hans Verkuil
2015-07-13 8:45 ` Hans Verkuil
2015-07-13 8:45 ` Hans Verkuil
2015-07-13 13:36 ` Jan Kara
2015-07-13 13:36 ` Jan Kara
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