Date:   Tue, 31 Jan 2017 13:12:05 +0100
From:   "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
To:     imre.deak@...el.com
Cc:     sedat.dilek@...il.com, "Rafael J. Wysocki" <rafael@...nel.org>,
        Jani Nikula <jani.nikula@...el.com>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        intel-gfx <intel-gfx@...ts.freedesktop.org>,
        the arch/x86 maintainers <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>, Pavel Machek <pavel@....cz>,
        Linux PM <linux-pm@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Chris Wilson <chris@...is-wilson.co.uk>
Subject: Re: [Intel-gfx] [Linux v4.10.0-rc1+] Still call-traces after
 suspend-resume (pm? i915? cpu/hotplug?)

On 1/31/2017 1:02 PM, Imre Deak wrote:
> On Tue, Jan 31, 2017 at 12:39:35PM +0100, Rafael J. Wysocki wrote:
>> On 1/31/2017 11:58 AM, Imre Deak wrote:
>>> Hi Rafael,
>> Hi,
>>
>>> 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@...nel.org> wrote:
>>>>>> On Fri, Dec 30, 2016 at 12:40 PM, Sedat Dilek <sedat.dilek@...il.com> wrote:
>>>>>>> Hi,
>>>>>>>
>>>>>>> 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
>>>>>>> drivers/base/power/runtime.c:1032
>>>>>>> [   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.
> Well, my point was that interrupts (or preemption) doesn't seem to get
> disabled anywhere on that path.

But the might_sleep_if() assertion in __pm_runtime_resume() triggers for 
some reason.  I wonder why then?

Of course, I may be overlooking something in the i915 code.

In any case, if you do

pm_runtime_get_sync(dev)
local_irq_disable()
pm_runtime_get_sync(dev)
<do something>
pm_runtime_put(dev)
local_irq_enable()
pm_runtime_put(dev)

that is technically correct, but it will cause the core to complain.

Thanks,
Rafael

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