Re: [Intel-gfx] [Linux v4.10.0-rc1+] Still call-traces after suspend-resume (pm? i915? cpu/hotplug?)

From: Rafael J. Wysocki
Date: Tue Jan 31 2017 - 06:40:10 EST

On 1/31/2017 11:58 AM, Imre Deak wrote:
Hi Rafael,


On Mon, Jan 30, 2017 at 11:44:37PM +0100, Rafael J. Wysocki wrote:
On 1/24/2017 2:33 AM, Sedat Dilek wrote:
On Fri, Dec 30, 2016 at 3:02 PM, Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote:
On Fri, Dec 30, 2016 at 12:40 PM, Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote:

I have already reported this issue in [1].
One of the issue was solved.
Unfortunately, it looks like there is still a different problem here
(Ubuntu/precise AMD64).

I tried v4.10-rc1 and latest Linus tree up to...

commit 98473f9f3f9bd404873cd1178c8be7d6d619f0d1
"mm/filemap: fix parameters to test_bit()"

Here we go...

[ 29.636047] BUG: sleeping function called from invalid context at
[ 29.636055] in_atomic(): 1, irqs_disabled(): 0, pid: 1500, name: Xorg
[ 29.636058] 1 lock held by Xorg/1500:
[ 29.636060] #0: (&dev->struct_mutex){+.+.+.}, at:
[<ffffffffa0680c13>] i915_mutex_lock_interruptible+0x43/0x140 [i915]
[ 29.636107] CPU: 0 PID: 1500 Comm: Xorg Not tainted
4.10.0-rc1-6-iniza-amd64 #1
[ 29.636109] Hardware name: SAMSUNG ELECTRONICS CO., LTD.
530U3BI/530U4BI/530U4BH/530U3BI/530U4BI/530U4BH, BIOS 13XK 03/28/2013
[ 29.636111] Call Trace:
[ 29.636120] dump_stack+0x85/0xc2
[ 29.636124] ___might_sleep+0x196/0x260
[ 29.636127] __might_sleep+0x53/0xb0
[ 29.636131] __pm_runtime_resume+0x7a/0x90
[ 29.636159] intel_runtime_pm_get+0x25/0x90 [i915]
[ 29.636189] aliasing_gtt_bind_vma+0xaa/0xf0 [i915]
[ 29.636220] i915_vma_bind+0xaf/0x1e0 [i915]
[ 29.636248] i915_gem_execbuffer_relocate_entry+0x513/0x6f0 [i915]
[ 29.636272] i915_gem_execbuffer_relocate_vma.isra.34+0x188/0x250 [i915]
[ 29.636275] ? trace_hardirqs_on+0xd/0x10
[ 29.636294] ? i915_gem_execbuffer_reserve_vma.isra.31+0x152/0x1f0 [i915]
[ 29.636316] ? i915_gem_execbuffer_reserve.isra.32+0x372/0x3a0 [i915]
[ 29.636342] i915_gem_do_execbuffer.isra.38+0xa70/0x1a40 [i915]
[ 29.636347] ? __might_fault+0x4e/0xb0
[ 29.636373] i915_gem_execbuffer2+0xc5/0x260 [i915]
[ 29.636376] ? __might_fault+0x4e/0xb0
[ 29.636395] drm_ioctl+0x206/0x450 [drm]
[ 29.636420] ? i915_gem_execbuffer+0x340/0x340 [i915]
[ 29.636425] ? __fget+0x5/0x200
[ 29.636429] do_vfs_ioctl+0x91/0x6f0
[ 29.636431] ? __fget+0x111/0x200
[ 29.636433] ? __fget+0x5/0x200
[ 29.636436] SyS_ioctl+0x79/0x90
[ 29.636441] entry_SYSCALL_64_fastpath+0x23/0xc6

On suspend/resume I see the same call trace.
[2] points to the "BUG" line.
Well, this appears to be an i915 issue, but not a serious one.

Clearly, a function that may sleep (pm_runtime_get_sync() in
intel_runtime_pm_get()) is called with disabled interrupts. If I
understand the code correctly, though, it actually is not going to
sleep in this particular case, because pm_runtime_get_sync() has
already been called once for this device in the same code path which
means that this particular instance will return immediately, so this
is a false-positive (most likely).
Not sure what's the root cause, but thought to clarify the above:

Yes, i915_gem_do_execbuffer() does take an RPM reference to optimize
things, so the RPM get in aliasing_gtt_bind_vma() won't need to resume
the device on this path. This isn't a guarantee though,
aliasing_gtt_bind_vma() could be called from other places without an RPM
reference. So preemption being disabled at that point is not
intentional. I also can't see where on the above path it would get
disabled due to a bug or otherwise.

The i915 code is correct AFAICS, but the core complains about a nested invocation of pm_runtime_get_sync() with disabled interrupts (which looks OK though), so the complaint is a false positive.

As I said, the way to go here appears to be to tweak the core, which I'm going to do.