Re: [Nouveau] [PATCH] drm/nouveau/dmem: missing mutex_lock in error path
On 6/14/19 10:39 AM, Ralph Campbell wrote: > On 6/13/19 5:49 PM, John Hubbard wrote: >> On 6/13/19 5:11 PM, Ralph Campbell wrote: ... >> Actually, the pre-existing code is a little concerning. Your change preserves >> the behavior, but it seems questionable to be doing a "return 0" (whether >> via the above break, or your change) when it's in this partially allocated >> state. It's reporting success when it only allocates part of what was >> requested, >> and it doesn't fill in the pages array either. >> >> >> >>> + return 0; >>> return ret; >>> } >>> + mutex_lock(>dmem->mutex); >>> continue; >>> } >>> >> >> The above comment is about pre-existing potential problems, but your patch >> itself >> looks correct, so: >> >> Reviewed-by: John Hubbard >> >> >> thanks, >> > The crash was the NULL pointer bug in Christoph's patch #10. > I sent a separate reply for that. > > Below is the console output I got, then I made the changes just based on > code inspection. Do you think I should include it in the change log? Yes, I think it's good to have it in there. If you look at git log, you'll see that it's common to include the symptoms, including the backtrace. It helps people see if they are hitting the same problem, for one thing. > > As for the "return 0", If you follow the call chain, > nouveau_dmem_pages_alloc() is only ever called for one page so this > currently "works" but I agree it is a bit of a time bomb. There are a > number of other bugs that I can see that need fixing but I think those > should be separate patches. > Yes of course. I called it out for the benefit of the email list, not to say that your patch needs any changes. thanks, -- John Hubbard NVIDIA ___ Nouveau mailing list Nouveau@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/nouveau
Re: [PATCH] drm/nouveau/dmem: missing mutex_lock in error path
On 6/13/19 5:49 PM, John Hubbard wrote:
On 6/13/19 5:11 PM, Ralph Campbell wrote:
In nouveau_dmem_pages_alloc(), the drm->dmem->mutex is unlocked before
calling nouveau_dmem_chunk_alloc().
Reacquire the lock before continuing to the next page.
Signed-off-by: Ralph Campbell
---
I found this while testing Jason Gunthorpe's hmm tree but this is
independent of those changes. I guess it could go through
David Airlie's tree for nouveau or Jason's tree.
Hi Ralph,
btw, was this the fix for the crash you were seeing? It might be nice to
mention in the commit description, if you are seeing real symptoms.
drivers/gpu/drm/nouveau/nouveau_dmem.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/nouveau/nouveau_dmem.c
b/drivers/gpu/drm/nouveau/nouveau_dmem.c
index 27aa4e72abe9..00f7236af1b9 100644
--- a/drivers/gpu/drm/nouveau/nouveau_dmem.c
+++ b/drivers/gpu/drm/nouveau/nouveau_dmem.c
@@ -379,9 +379,10 @@ nouveau_dmem_pages_alloc(struct nouveau_drm *drm,
ret = nouveau_dmem_chunk_alloc(drm);
if (ret) {
if (c)
- break;
Actually, the pre-existing code is a little concerning. Your change preserves
the behavior, but it seems questionable to be doing a "return 0" (whether
via the above break, or your change) when it's in this partially allocated
state. It's reporting success when it only allocates part of what was requested,
and it doesn't fill in the pages array either.
+ return 0;
return ret;
}
+ mutex_lock(>dmem->mutex);
continue;
}
The above comment is about pre-existing potential problems, but your patch
itself
looks correct, so:
Reviewed-by: John Hubbard
thanks,
The crash was the NULL pointer bug in Christoph's patch #10.
I sent a separate reply for that.
Below is the console output I got, then I made the changes just based on
code inspection. Do you think I should include it in the change log?
As for the "return 0", If you follow the call chain,
nouveau_dmem_pages_alloc() is only ever called for one page so this
currently "works" but I agree it is a bit of a time bomb. There are a
number of other bugs that I can see that need fixing but I think those
should be separate patches.
[ 1294.871933] =
[ 1294.876656] WARNING: bad unlock balance detected!
[ 1294.881375] 5.2.0-rc3+ #5 Not tainted
[ 1294.885048] -
[ 1294.889773] test-malloc-vra/6299 is trying to release lock
(>dmem->mutex) at:
[ 1294.897482] []
nouveau_dmem_migrate_alloc_and_copy+0x79f/0xbf0 [nouveau]
[ 1294.905782] but there are no more locks to release!
[ 1294.910690]
[ 1294.910690] other info that might help us debug this:
[ 1294.917249] 1 lock held by test-malloc-vra/6299:
[ 1294.921881] #0: 16e10454 (>mmap_sem#2){}, at:
nouveau_svmm_bind+0x142/0x210 [nouveau]
[ 1294.931313]
[ 1294.931313] stack backtrace:
[ 1294.935702] CPU: 4 PID: 6299 Comm: test-malloc-vra Not tainted
5.2.0-rc3+ #5
[ 1294.942786] Hardware name: ASUS X299-A/PRIME X299-A, BIOS 1401 05/21/2018
[ 1294.949590] Call Trace:
[ 1294.952059] dump_stack+0x7c/0xc0
[ 1294.955469] ? nouveau_dmem_migrate_alloc_and_copy+0x79f/0xbf0 [nouveau]
[ 1294.962213] print_unlock_imbalance_bug.cold.52+0xca/0xcf
[ 1294.967641] lock_release+0x306/0x380
[ 1294.971383] ? nouveau_dmem_migrate_alloc_and_copy+0x79f/0xbf0 [nouveau]
[ 1294.978089] ? lock_downgrade+0x2d0/0x2d0
[ 1294.982121] ? find_held_lock+0xac/0xd0
[ 1294.985979] __mutex_unlock_slowpath+0x8f/0x3f0
[ 1294.990540] ? wait_for_completion+0x230/0x230
[ 1294.995002] ? rwlock_bug.part.2+0x60/0x60
[ 1294.999197] nouveau_dmem_migrate_alloc_and_copy+0x79f/0xbf0 [nouveau]
[ 1295.005751] ? page_mapping+0x98/0x110
[ 1295.009511] migrate_vma+0xa74/0x1090
[ 1295.013186] ? move_to_new_page+0x480/0x480
[ 1295.017400] ? __kmalloc+0x153/0x300
[ 1295.021052] ? nouveau_dmem_migrate_vma+0xd8/0x1e0 [nouveau]
[ 1295.026796] nouveau_dmem_migrate_vma+0x157/0x1e0 [nouveau]
[ 1295.032466] ? nouveau_dmem_init+0x490/0x490 [nouveau]
[ 1295.037612] ? vmacache_find+0xc2/0x110
[ 1295.041537] nouveau_svmm_bind+0x1b4/0x210 [nouveau]
[ 1295.046583] ? nouveau_svm_fault+0x13e0/0x13e0 [nouveau]
[ 1295.051912] drm_ioctl_kernel+0x14d/0x1a0
[ 1295.055930] ? drm_setversion+0x330/0x330
[ 1295.059971] drm_ioctl+0x308/0x530
[ 1295.063384] ? drm_version+0x150/0x150
[ 1295.067153] ? find_held_lock+0xac/0xd0
[ 1295.070996] ? __pm_runtime_resume+0x3f/0xa0
[ 1295.075285] ? mark_held_locks+0x29/0xa0
[ 1295.079230] ? _raw_spin_unlock_irqrestore+0x3c/0x50
[ 1295.084232] ? lockdep_hardirqs_on+0x17d/0x250
[ 1295.088768] nouveau_drm_ioctl+0x9a/0x100 [nouveau]
[ 1295.093661] do_vfs_ioctl+0x137/0x9a0
[ 1295.097341] ? ioctl_preallocate+0x140/0x140
Re: [Nouveau] [PATCH] drm/nouveau/dmem: missing mutex_lock in error path
On 6/13/19 5:11 PM, Ralph Campbell wrote:
> In nouveau_dmem_pages_alloc(), the drm->dmem->mutex is unlocked before
> calling nouveau_dmem_chunk_alloc().
> Reacquire the lock before continuing to the next page.
>
> Signed-off-by: Ralph Campbell
> ---
>
> I found this while testing Jason Gunthorpe's hmm tree but this is
> independant of those changes. I guess it could go through
> David Airlie's tree for nouveau or Jason's tree.
>
Hi Ralph,
btw, was this the fix for the crash you were seeing? It might be nice to
mention in the commit description, if you are seeing real symptoms.
> drivers/gpu/drm/nouveau/nouveau_dmem.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/nouveau/nouveau_dmem.c
> b/drivers/gpu/drm/nouveau/nouveau_dmem.c
> index 27aa4e72abe9..00f7236af1b9 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_dmem.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_dmem.c
> @@ -379,9 +379,10 @@ nouveau_dmem_pages_alloc(struct nouveau_drm *drm,
> ret = nouveau_dmem_chunk_alloc(drm);
> if (ret) {
> if (c)
> - break;
Actually, the pre-existing code is a little concerning. Your change preserves
the behavior, but it seems questionable to be doing a "return 0" (whether
via the above break, or your change) when it's in this partially allocated
state. It's reporting success when it only allocates part of what was requested,
and it doesn't fill in the pages array either.
> + return 0;
> return ret;
> }
> + mutex_lock(>dmem->mutex);
> continue;
> }
>
>
The above comment is about pre-existing potential problems, but your patch
itself
looks correct, so:
Reviewed-by: John Hubbard
thanks,
--
John Hubbard
NVIDIA
___
Nouveau mailing list
Nouveau@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/nouveau
Re: [Nouveau] [PATCH] drm/nouveau/dmem: missing mutex_lock in error path
On Thu, Jun 13, 2019 at 05:11:21PM -0700, Ralph Campbell wrote: > In nouveau_dmem_pages_alloc(), the drm->dmem->mutex is unlocked before > calling nouveau_dmem_chunk_alloc(). > Reacquire the lock before continuing to the next page. > > Signed-off-by: Ralph Campbell > --- > > I found this while testing Jason Gunthorpe's hmm tree but this is > independant of those changes. I guess it could go through > David Airlie's tree for nouveau or Jason's tree. This seems like a bad enough bug to send it into -rc? It probably should go through the normal nouveau channels, thanks Jason ___ Nouveau mailing list Nouveau@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/nouveau
[PATCH] drm/nouveau/dmem: missing mutex_lock in error path
In nouveau_dmem_pages_alloc(), the drm->dmem->mutex is unlocked before
calling nouveau_dmem_chunk_alloc().
Reacquire the lock before continuing to the next page.
Signed-off-by: Ralph Campbell
---
I found this while testing Jason Gunthorpe's hmm tree but this is
independant of those changes. I guess it could go through
David Airlie's tree for nouveau or Jason's tree.
drivers/gpu/drm/nouveau/nouveau_dmem.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/nouveau/nouveau_dmem.c
b/drivers/gpu/drm/nouveau/nouveau_dmem.c
index 27aa4e72abe9..00f7236af1b9 100644
--- a/drivers/gpu/drm/nouveau/nouveau_dmem.c
+++ b/drivers/gpu/drm/nouveau/nouveau_dmem.c
@@ -379,9 +379,10 @@ nouveau_dmem_pages_alloc(struct nouveau_drm *drm,
ret = nouveau_dmem_chunk_alloc(drm);
if (ret) {
if (c)
- break;
+ return 0;
return ret;
}
+ mutex_lock(>dmem->mutex);
continue;
}
--
2.20.1
