Hi Chris,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on drm-intel/for-linux-next]
[also build test ERROR on v5.0-rc1 next-20190108]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Chris-Wilson/drm-i915-Track-all-held-rpm-wakerefs/20190108-233439
base:   git://anongit.freedesktop.org/drm-intel for-linux-next
config: x86_64-randconfig-s5-01090236 (attached as .config)
compiler: gcc-7 (Debian 7.3.0-1) 7.3.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

All errors (new ones prefixed by >>):

   drivers/gpu/drm/i915/intel_runtime_pm.o: In function `__print_intel_runtime_pm_wakeref':
>> drivers/gpu/drm/i915/intel_runtime_pm.c:154: undefined reference to `depot_fetch_stack'
>> drivers/gpu/drm/i915/intel_runtime_pm.c:154: undefined reference to `depot_fetch_stack'
>> drivers/gpu/drm/i915/intel_runtime_pm.c:154: undefined reference to `depot_fetch_stack'
>> drivers/gpu/drm/i915/intel_runtime_pm.c:154: undefined reference to `depot_fetch_stack'
   drivers/gpu/drm/i915/intel_runtime_pm.o: In function `track_intel_runtime_pm_wakeref':
>> drivers/gpu/drm/i915/intel_runtime_pm.c:86: undefined reference to `depot_save_stack'

vim +154 drivers/gpu/drm/i915/intel_runtime_pm.c

    64	
    65	static noinline void
    66	track_intel_runtime_pm_wakeref(struct drm_i915_private *i915)
    67	{
    68		struct i915_runtime_pm *rpm = &i915->runtime_pm;
    69		unsigned long entries[STACKDEPTH];
    70		struct stack_trace trace = {
    71			.entries = entries,
    72			.max_entries = ARRAY_SIZE(entries),
    73			.skip = 0 /* gcc is ignoring noinline for tail calls? */
    74		};
    75		unsigned long flags;
    76		depot_stack_handle_t stack, *stacks;
    77	
    78		if (!HAS_RUNTIME_PM(i915))
    79			return;
    80	
    81		save_stack_trace(&trace);
    82		if (trace.nr_entries &&
    83		    trace.entries[trace.nr_entries - 1] == ULONG_MAX)
    84			trace.nr_entries--;
    85	
  > 86		stack = depot_save_stack(&trace, GFP_NOWAIT | __GFP_NOWARN);
    87		if (!stack)
    88			return;
    89	
    90		spin_lock_irqsave(&rpm->debug_lock, flags);
    91		stacks = krealloc(rpm->debug_owners,
    92				  (rpm->debug_count + 1) * sizeof(*stacks),
    93				  GFP_NOWAIT | __GFP_NOWARN);
    94		if (stacks) {
    95			stacks[rpm->debug_count++] = stack;
    96			rpm->debug_owners = stacks;
    97		}
    98		spin_unlock_irqrestore(&rpm->debug_lock, flags);
    99	}
   100	
   101	static void untrack_intel_runtime_pm_wakeref(struct drm_i915_private *i915)
   102	{
   103		struct i915_runtime_pm *rpm = &i915->runtime_pm;
   104		depot_stack_handle_t *stacks;
   105		unsigned long flags;
   106	
   107		spin_lock_irqsave(&rpm->debug_lock, flags);
   108		stacks = fetch_and_zero(&rpm->debug_owners);
   109		rpm->debug_count = 0;
   110		spin_unlock_irqrestore(&rpm->debug_lock, flags);
   111	
   112		kfree(stacks);
   113	}
   114	
   115	static int cmphandle(const void *_a, const void *_b)
   116	{
   117		const depot_stack_handle_t * const a = _a, * const b = _b;
   118	
   119		if (*a < *b)
   120			return -1;
   121		else if (*a > *b)
   122			return 1;
   123		else
   124			return 0;
   125	}
   126	
   127	static void __print_intel_runtime_pm_wakeref(struct drm_printer *p,
   128						     depot_stack_handle_t *stacks,
   129						     unsigned long count)
   130	{
   131		unsigned long entries[STACKDEPTH];
   132		unsigned long i;
   133		char *buf;
   134	
   135		drm_printf(p, "Wakeref count: %lu\n", count);
   136	
   137		buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
   138		if (!buf)
   139			return;
   140	
   141		sort(stacks, count, sizeof(*stacks), cmphandle, NULL);
   142	
   143		for (i = 0; i < count; i++) {
   144			struct stack_trace trace = {
   145				.entries = entries,
   146				.max_entries = ARRAY_SIZE(entries),
   147			};
   148			depot_stack_handle_t stack = stacks[i];
   149			unsigned long rep;
   150	
   151			rep = 1;
   152			while (i + 1 < count && stacks[i + 1] == stack)
   153				rep++, i++;
 > 154			depot_fetch_stack(stack, &trace);
   155			snprint_stack_trace(buf, PAGE_SIZE, &trace, 2);
   156			drm_printf(p, "Wakeref x%lu taken at:\n%s", rep, buf);
   157		}
   158	
   159		kfree(buf);
   160	}
   161	

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