Messages in this thread | | | Subject | Re: [x86_64] 2.6.14-git13 mplayer fails with "v4l2: ioctl queue buffer failed: Bad address" (2 Nov 2005, 11 Nov 2005) | From | "Nickolay V. Shmyrev" <> | Date | Wed, 16 Nov 2005 15:50:54 +0300 |
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В Вск, 13/11/2005 в 04:54 +0200, Matti Aarnio пишет: > On Sun, Nov 13, 2005 at 01:22:51AM +0300, Nickolay V. Shmyrev wrote: > > Hello all. > > > > We have even found the hack that fix that problem: > > A hack, but working one.. > (for the small while that I tested it) > > > Index: linux/drivers/media/video/video-buf.c > > =================================================================== > > RCS file: /cvs/video4linux/v4l-kernel/linux/drivers/media/video/video-buf.c,v > > retrieving revision 1.21 > > diff -u -p -r1.21 video-buf.c > > --- linux/drivers/media/video/video-buf.c 16 Oct 2005 12:13:58 -0000 > > +++ linux/drivers/media/video/video-buf.c 12 Nov 2005 22:19:13 -0000 > > @@ -1248,7 +1248,7 @@ int videobuf_mmap_mapper(struct videobuf > > map->end = vma->vm_end; > > map->q = q; > > vma->vm_ops = &videobuf_vm_ops; > > - vma->vm_flags |= VM_DONTEXPAND | VM_RESERVED; > > + vma->vm_flags |= VM_DONTEXPAND; > > vma->vm_flags &= ~VM_IO; /* using shared anonymous pages */ > > vma->vm_private_data = map; > > dprintk(1,"mmap %p: q=%p %08lx-%08lx pgoff %08lx bufs %d-%d\n", > > > > Somehow since 2.6.15-rc1 VM_RESERVED makes get_user_pages return EFAULT. > > I don't know the exact reason of that behavior and the correct way to fix > > that problem. Just kernel interfaces changed once again, the old > > point everyone knows. So if someone can explain it, that would be helpful. > > This EFAULT rejection is due to change in get_user_pages() function > in mm/memory.c file of 2.6.14-git2 > > > @@ -945,8 +947,8 @@ int get_user_pages(struct task_struct *t > continue; > } > > - if (!vma || (vma->vm_flags & VM_IO) > - || !(flags & vma->vm_flags)) > + if (!vma || (vma->vm_flags & (VM_IO | VM_RESERVED)) > + || !(vm_flags & vma->vm_flags)) > return i ? : -EFAULT; > > if (is_vm_hugetlb_page(vma)) { > > > I don't know how to use git tools to see, whose patch actually > did this particular change. > > > /Matti Aarnio
It's sad, but I still don't understand the way it should be fixed. Removal of VM_RESERVED is certainly not a solution, since we don't going to swap mmaped pages and VM_RESERVED is used in other drivers (for example, some sound drivers)
So, we need to find the problem itself. After looking at the code I've found that the x86_64 dependency of that problem lies in the check in memory.c:get_user_pages
if (vma && in_gate_area (task, start))
x86_64 defines it's own arch-dependant function in_gate_area which fails in our case. Can someone trace that code and find why do we fail and fail only on x86_64. It would be nice if someone could point me to get_user_pages documentation, why it's so differently behaves for 64 bit arch.
Also it seems that I had traces of video-buf module with debug enabled on 64 bit, but lost them. Can someone just enable debug option to video- buf module and collect those traces.
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