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* [PATCH] lib/stackdepot: allow optional init and stack_table allocation by kvmalloc()
@ 2021-10-07  9:58 Vlastimil Babka
  2021-10-07 11:01 ` Dmitry Vyukov
  2021-10-07 11:01 ` Marco Elver
  0 siblings, 2 replies; 6+ messages in thread
From: Vlastimil Babka @ 2021-10-07  9:58 UTC (permalink / raw)
  To: Andrew Morton
  Cc: linux-mm, linux-kernel, dri-devel, intel-gfx, kasan-dev,
	Vlastimil Babka, Marco Elver, Vijayanand Jitta,
	Maarten Lankhorst, Maxime Ripard, Thomas Zimmermann,
	David Airlie, Daniel Vetter, Andrey Ryabinin,
	Alexander Potapenko, Andrey Konovalov, Dmitry Vyukov,
	Geert Uytterhoeven, Oliver Glitta, Imran Khan

Currently, enabling CONFIG_STACKDEPOT means its stack_table will be allocated
from memblock, even if stack depot ends up not actually used. The default size
of stack_table is 4MB on 32-bit, 8MB on 64-bit.

This is fine for use-cases such as KASAN which is also a config option and
has overhead on its own. But it's an issue for functionality that has to be
actually enabled on boot (page_owner) or depends on hardware (GPU drivers)
and thus the memory might be wasted. This was raised as an issue when trying
to add stackdepot support for SLUB's debug object tracking functionality. It's
common to build kernels with CONFIG_SLUB_DEBUG and enable slub_debug on boot
only when needed, or create specific kmem caches with debugging for testing
purposes.

It would thus be more efficient if stackdepot's table was allocated only when
actually going to be used. This patch thus makes the allocation (and whole
stack_depot_init() call) optional:

- Add a CONFIG_STACKDEPOT_ALWAYS_INIT flag to keep using the current
  well-defined point of allocation as part of mem_init(). Make CONFIG_KASAN
  select this flag.
- Other users have to call stack_depot_init() as part of their own init when
  it's determined that stack depot will actually be used. This may depend on
  both config and runtime conditions. Convert current users which are
  page_owner and several in the DRM subsystem. Same will be done for SLUB
  later.
- Because the init might now be called after the boot-time memblock allocation
  has given all memory to the buddy allocator, change stack_depot_init() to
  allocate stack_table with kvmalloc() when memblock is no longer available.
  Also handle allocation failure by disabling stackdepot (could have
  theoretically happened even with memblock allocation previously), and don't
  unnecessarily align the memblock allocation to its own size anymore.

[1] https://lore.kernel.org/all/CAMuHMdW=eoVzM1Re5FVoEN87nKfiLmM2+Ah7eNu2KXEhCvbZyA@mail.gmail.com/

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Marco Elver <elver@google.com>
Cc: Vijayanand Jitta <vjitta@codeaurora.org>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Oliver Glitta <glittao@gmail.com>
Cc: Imran Khan <imran.f.khan@oracle.com>
---
Hi, I'd appreciate review of the DRM parts - namely that I've got correctly
that stack_depot_init() is called from the proper init functions and iff
stack_depot_save() is going to be used later. Thanks!

 drivers/gpu/drm/drm_dp_mst_topology.c   |  1 +
 drivers/gpu/drm/drm_mm.c                |  4 ++++
 drivers/gpu/drm/i915/intel_runtime_pm.c |  3 +++
 include/linux/stackdepot.h              | 19 ++++++++-------
 init/main.c                             |  3 ++-
 lib/Kconfig                             |  3 +++
 lib/Kconfig.kasan                       |  1 +
 lib/stackdepot.c                        | 32 +++++++++++++++++++++----
 mm/page_owner.c                         |  2 ++
 9 files changed, 53 insertions(+), 15 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 2d1adab9e360..bbe972d59dae 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -5490,6 +5490,7 @@ int drm_dp_mst_topology_mgr_init(struct drm_dp_mst_topology_mgr *mgr,
 	mutex_init(&mgr->probe_lock);
 #if IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS)
 	mutex_init(&mgr->topology_ref_history_lock);
+	stack_depot_init();
 #endif
 	INIT_LIST_HEAD(&mgr->tx_msg_downq);
 	INIT_LIST_HEAD(&mgr->destroy_port_list);
diff --git a/drivers/gpu/drm/drm_mm.c b/drivers/gpu/drm/drm_mm.c
index 7d1c578388d3..8257f9d4f619 100644
--- a/drivers/gpu/drm/drm_mm.c
+++ b/drivers/gpu/drm/drm_mm.c
@@ -980,6 +980,10 @@ void drm_mm_init(struct drm_mm *mm, u64 start, u64 size)
 	add_hole(&mm->head_node);
 
 	mm->scan_active = 0;
+
+#ifdef CONFIG_DRM_DEBUG_MM
+	stack_depot_init();
+#endif
 }
 EXPORT_SYMBOL(drm_mm_init);
 
diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
index 0d85f3c5c526..806c32ab410b 100644
--- a/drivers/gpu/drm/i915/intel_runtime_pm.c
+++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
@@ -68,6 +68,9 @@ static noinline depot_stack_handle_t __save_depot_stack(void)
 static void init_intel_runtime_pm_wakeref(struct intel_runtime_pm *rpm)
 {
 	spin_lock_init(&rpm->debug.lock);
+
+	if (rpm->available)
+		stack_depot_init();
 }
 
 static noinline depot_stack_handle_t
diff --git a/include/linux/stackdepot.h b/include/linux/stackdepot.h
index c34b55a6e554..60ba99a43745 100644
--- a/include/linux/stackdepot.h
+++ b/include/linux/stackdepot.h
@@ -15,6 +15,16 @@
 
 typedef u32 depot_stack_handle_t;
 
+/*
+ * Every user of stack depot has to call this during its own init when it's
+ * decided that it will be calling stack_depot_save() later.
+ *
+ * The alternative is to select STACKDEPOT_ALWAYS_INIT to have stack depot
+ * enabled as part of mm_init(), for subsystems where it's known at compile time
+ * that stack depot will be used.
+ */
+int stack_depot_init(void);
+
 depot_stack_handle_t __stack_depot_save(unsigned long *entries,
 					unsigned int nr_entries,
 					gfp_t gfp_flags, bool can_alloc);
@@ -30,13 +40,4 @@ int stack_depot_snprint(depot_stack_handle_t handle, char *buf, size_t size,
 
 void stack_depot_print(depot_stack_handle_t stack);
 
-#ifdef CONFIG_STACKDEPOT
-int stack_depot_init(void);
-#else
-static inline int stack_depot_init(void)
-{
-	return 0;
-}
-#endif	/* CONFIG_STACKDEPOT */
-
 #endif
diff --git a/init/main.c b/init/main.c
index ee4d3e1b3eb9..b6a5833d98f5 100644
--- a/init/main.c
+++ b/init/main.c
@@ -844,7 +844,8 @@ static void __init mm_init(void)
 	init_mem_debugging_and_hardening();
 	kfence_alloc_pool();
 	report_meminit();
-	stack_depot_init();
+	if (IS_ENABLED(CONFIG_STACKDEPOT_ALWAYS_INIT))
+		stack_depot_init();
 	mem_init();
 	mem_init_print_info();
 	/* page_owner must be initialized after buddy is ready */
diff --git a/lib/Kconfig b/lib/Kconfig
index 5e7165e6a346..df6bcf0a4cc3 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -671,6 +671,9 @@ config STACKDEPOT
 	bool
 	select STACKTRACE
 
+config STACKDEPOT_ALWAYS_INIT
+	bool
+
 config STACK_HASH_ORDER
 	int "stack depot hash size (12 => 4KB, 20 => 1024KB)"
 	range 12 20
diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
index cdc842d090db..695deb603c66 100644
--- a/lib/Kconfig.kasan
+++ b/lib/Kconfig.kasan
@@ -39,6 +39,7 @@ menuconfig KASAN
 		   HAVE_ARCH_KASAN_HW_TAGS
 	depends on (SLUB && SYSFS) || (SLAB && !DEBUG_SLAB)
 	select STACKDEPOT
+	select STACKDEPOT_ALWAYS_INIT
 	help
 	  Enables KASAN (KernelAddressSANitizer) - runtime memory debugger,
 	  designed to find out-of-bounds accesses and use-after-free bugs.
diff --git a/lib/stackdepot.c b/lib/stackdepot.c
index b437ae79aca1..a4f449ccd0dc 100644
--- a/lib/stackdepot.c
+++ b/lib/stackdepot.c
@@ -23,6 +23,7 @@
 #include <linux/jhash.h>
 #include <linux/kernel.h>
 #include <linux/mm.h>
+#include <linux/mutex.h>
 #include <linux/percpu.h>
 #include <linux/printk.h>
 #include <linux/slab.h>
@@ -145,6 +146,7 @@ depot_alloc_stack(unsigned long *entries, int size, u32 hash, void **prealloc)
 #define STACK_HASH_MASK (STACK_HASH_SIZE - 1)
 #define STACK_HASH_SEED 0x9747b28c
 
+DEFINE_MUTEX(stack_depot_init_mutex);
 static bool stack_depot_disable;
 static struct stack_record **stack_table;
 
@@ -161,18 +163,38 @@ static int __init is_stack_depot_disabled(char *str)
 }
 early_param("stack_depot_disable", is_stack_depot_disabled);
 
-int __init stack_depot_init(void)
+/*
+ * __ref because of memblock_alloc(), which will not be actually called after
+ * the __init code is gone
+ */
+__ref int stack_depot_init(void)
 {
-	if (!stack_depot_disable) {
+	mutex_lock(&stack_depot_init_mutex);
+	if (!stack_depot_disable && stack_table == NULL) {
 		size_t size = (STACK_HASH_SIZE * sizeof(struct stack_record *));
 		int i;
 
-		stack_table = memblock_alloc(size, size);
-		for (i = 0; i < STACK_HASH_SIZE;  i++)
-			stack_table[i] = NULL;
+		if (slab_is_available()) {
+			pr_info("Stack Depot allocating hash table with kvmalloc\n");
+			stack_table = kvmalloc(size, GFP_KERNEL);
+		} else {
+			pr_info("Stack Depot allocating hash table with memblock_alloc\n");
+			stack_table = memblock_alloc(size, SMP_CACHE_BYTES);
+		}
+		if (stack_table) {
+			for (i = 0; i < STACK_HASH_SIZE;  i++)
+				stack_table[i] = NULL;
+		} else {
+			pr_err("Stack Depot failed hash table allocationg, disabling\n");
+			stack_depot_disable = true;
+			mutex_unlock(&stack_depot_init_mutex);
+			return -ENOMEM;
+		}
 	}
+	mutex_unlock(&stack_depot_init_mutex);
 	return 0;
 }
+EXPORT_SYMBOL_GPL(stack_depot_init);
 
 /* Calculate hash for a stack */
 static inline u32 hash_stack(unsigned long *entries, unsigned int size)
diff --git a/mm/page_owner.c b/mm/page_owner.c
index a83f546c06b5..a48607b51a97 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -80,6 +80,8 @@ static void init_page_owner(void)
 	if (!page_owner_enabled)
 		return;
 
+	stack_depot_init();
+
 	register_dummy_stack();
 	register_failure_stack();
 	register_early_stack();
-- 
2.33.0


^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH] lib/stackdepot: allow optional init and stack_table allocation by kvmalloc()
  2021-10-07  9:58 [PATCH] lib/stackdepot: allow optional init and stack_table allocation by kvmalloc() Vlastimil Babka
@ 2021-10-07 11:01 ` Dmitry Vyukov
  2021-10-07 11:01 ` Marco Elver
  1 sibling, 0 replies; 6+ messages in thread
From: Dmitry Vyukov @ 2021-10-07 11:01 UTC (permalink / raw)
  To: Vlastimil Babka
  Cc: Andrew Morton, linux-mm, linux-kernel, dri-devel, intel-gfx,
	kasan-dev, Marco Elver, Vijayanand Jitta, Maarten Lankhorst,
	Maxime Ripard, Thomas Zimmermann, David Airlie, Daniel Vetter,
	Andrey Ryabinin, Alexander Potapenko, Andrey Konovalov,
	Geert Uytterhoeven, Oliver Glitta, Imran Khan

On Thu, 7 Oct 2021 at 11:58, Vlastimil Babka <vbabka@suse.cz> wrote:
>
> Currently, enabling CONFIG_STACKDEPOT means its stack_table will be allocated
> from memblock, even if stack depot ends up not actually used. The default size
> of stack_table is 4MB on 32-bit, 8MB on 64-bit.
>
> This is fine for use-cases such as KASAN which is also a config option and
> has overhead on its own. But it's an issue for functionality that has to be
> actually enabled on boot (page_owner) or depends on hardware (GPU drivers)
> and thus the memory might be wasted. This was raised as an issue when trying
> to add stackdepot support for SLUB's debug object tracking functionality. It's
> common to build kernels with CONFIG_SLUB_DEBUG and enable slub_debug on boot
> only when needed, or create specific kmem caches with debugging for testing
> purposes.
>
> It would thus be more efficient if stackdepot's table was allocated only when
> actually going to be used. This patch thus makes the allocation (and whole
> stack_depot_init() call) optional:
>
> - Add a CONFIG_STACKDEPOT_ALWAYS_INIT flag to keep using the current
>   well-defined point of allocation as part of mem_init(). Make CONFIG_KASAN
>   select this flag.
> - Other users have to call stack_depot_init() as part of their own init when
>   it's determined that stack depot will actually be used. This may depend on
>   both config and runtime conditions. Convert current users which are
>   page_owner and several in the DRM subsystem. Same will be done for SLUB
>   later.
> - Because the init might now be called after the boot-time memblock allocation
>   has given all memory to the buddy allocator, change stack_depot_init() to
>   allocate stack_table with kvmalloc() when memblock is no longer available.
>   Also handle allocation failure by disabling stackdepot (could have
>   theoretically happened even with memblock allocation previously), and don't
>   unnecessarily align the memblock allocation to its own size anymore.
>
> [1] https://lore.kernel.org/all/CAMuHMdW=eoVzM1Re5FVoEN87nKfiLmM2+Ah7eNu2KXEhCvbZyA@mail.gmail.com/
>
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
> Cc: Marco Elver <elver@google.com>
> Cc: Vijayanand Jitta <vjitta@codeaurora.org>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: Maxime Ripard <mripard@kernel.org>
> Cc: Thomas Zimmermann <tzimmermann@suse.de>
> Cc: David Airlie <airlied@linux.ie>
> Cc: Daniel Vetter <daniel@ffwll.ch>
> Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
> Cc: Alexander Potapenko <glider@google.com>
> Cc: Andrey Konovalov <andreyknvl@gmail.com>
> Cc: Dmitry Vyukov <dvyukov@google.com>
> Cc: Geert Uytterhoeven <geert@linux-m68k.org>
> Cc: Oliver Glitta <glittao@gmail.com>
> Cc: Imran Khan <imran.f.khan@oracle.com>

Acked-by: Dmitry Vyukov <dvyukov@google.com>

> ---
> Hi, I'd appreciate review of the DRM parts - namely that I've got correctly
> that stack_depot_init() is called from the proper init functions and iff
> stack_depot_save() is going to be used later. Thanks!
>
>  drivers/gpu/drm/drm_dp_mst_topology.c   |  1 +
>  drivers/gpu/drm/drm_mm.c                |  4 ++++
>  drivers/gpu/drm/i915/intel_runtime_pm.c |  3 +++
>  include/linux/stackdepot.h              | 19 ++++++++-------
>  init/main.c                             |  3 ++-
>  lib/Kconfig                             |  3 +++
>  lib/Kconfig.kasan                       |  1 +
>  lib/stackdepot.c                        | 32 +++++++++++++++++++++----
>  mm/page_owner.c                         |  2 ++
>  9 files changed, 53 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
> index 2d1adab9e360..bbe972d59dae 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -5490,6 +5490,7 @@ int drm_dp_mst_topology_mgr_init(struct drm_dp_mst_topology_mgr *mgr,
>         mutex_init(&mgr->probe_lock);
>  #if IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS)
>         mutex_init(&mgr->topology_ref_history_lock);
> +       stack_depot_init();
>  #endif
>         INIT_LIST_HEAD(&mgr->tx_msg_downq);
>         INIT_LIST_HEAD(&mgr->destroy_port_list);
> diff --git a/drivers/gpu/drm/drm_mm.c b/drivers/gpu/drm/drm_mm.c
> index 7d1c578388d3..8257f9d4f619 100644
> --- a/drivers/gpu/drm/drm_mm.c
> +++ b/drivers/gpu/drm/drm_mm.c
> @@ -980,6 +980,10 @@ void drm_mm_init(struct drm_mm *mm, u64 start, u64 size)
>         add_hole(&mm->head_node);
>
>         mm->scan_active = 0;
> +
> +#ifdef CONFIG_DRM_DEBUG_MM
> +       stack_depot_init();
> +#endif
>  }
>  EXPORT_SYMBOL(drm_mm_init);
>
> diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
> index 0d85f3c5c526..806c32ab410b 100644
> --- a/drivers/gpu/drm/i915/intel_runtime_pm.c
> +++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
> @@ -68,6 +68,9 @@ static noinline depot_stack_handle_t __save_depot_stack(void)
>  static void init_intel_runtime_pm_wakeref(struct intel_runtime_pm *rpm)
>  {
>         spin_lock_init(&rpm->debug.lock);
> +
> +       if (rpm->available)
> +               stack_depot_init();
>  }
>
>  static noinline depot_stack_handle_t
> diff --git a/include/linux/stackdepot.h b/include/linux/stackdepot.h
> index c34b55a6e554..60ba99a43745 100644
> --- a/include/linux/stackdepot.h
> +++ b/include/linux/stackdepot.h
> @@ -15,6 +15,16 @@
>
>  typedef u32 depot_stack_handle_t;
>
> +/*
> + * Every user of stack depot has to call this during its own init when it's
> + * decided that it will be calling stack_depot_save() later.
> + *
> + * The alternative is to select STACKDEPOT_ALWAYS_INIT to have stack depot
> + * enabled as part of mm_init(), for subsystems where it's known at compile time
> + * that stack depot will be used.
> + */
> +int stack_depot_init(void);
> +
>  depot_stack_handle_t __stack_depot_save(unsigned long *entries,
>                                         unsigned int nr_entries,
>                                         gfp_t gfp_flags, bool can_alloc);
> @@ -30,13 +40,4 @@ int stack_depot_snprint(depot_stack_handle_t handle, char *buf, size_t size,
>
>  void stack_depot_print(depot_stack_handle_t stack);
>
> -#ifdef CONFIG_STACKDEPOT
> -int stack_depot_init(void);
> -#else
> -static inline int stack_depot_init(void)
> -{
> -       return 0;
> -}
> -#endif /* CONFIG_STACKDEPOT */
> -
>  #endif
> diff --git a/init/main.c b/init/main.c
> index ee4d3e1b3eb9..b6a5833d98f5 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -844,7 +844,8 @@ static void __init mm_init(void)
>         init_mem_debugging_and_hardening();
>         kfence_alloc_pool();
>         report_meminit();
> -       stack_depot_init();
> +       if (IS_ENABLED(CONFIG_STACKDEPOT_ALWAYS_INIT))
> +               stack_depot_init();
>         mem_init();
>         mem_init_print_info();
>         /* page_owner must be initialized after buddy is ready */
> diff --git a/lib/Kconfig b/lib/Kconfig
> index 5e7165e6a346..df6bcf0a4cc3 100644
> --- a/lib/Kconfig
> +++ b/lib/Kconfig
> @@ -671,6 +671,9 @@ config STACKDEPOT
>         bool
>         select STACKTRACE
>
> +config STACKDEPOT_ALWAYS_INIT
> +       bool
> +
>  config STACK_HASH_ORDER
>         int "stack depot hash size (12 => 4KB, 20 => 1024KB)"
>         range 12 20
> diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
> index cdc842d090db..695deb603c66 100644
> --- a/lib/Kconfig.kasan
> +++ b/lib/Kconfig.kasan
> @@ -39,6 +39,7 @@ menuconfig KASAN
>                    HAVE_ARCH_KASAN_HW_TAGS
>         depends on (SLUB && SYSFS) || (SLAB && !DEBUG_SLAB)
>         select STACKDEPOT
> +       select STACKDEPOT_ALWAYS_INIT
>         help
>           Enables KASAN (KernelAddressSANitizer) - runtime memory debugger,
>           designed to find out-of-bounds accesses and use-after-free bugs.
> diff --git a/lib/stackdepot.c b/lib/stackdepot.c
> index b437ae79aca1..a4f449ccd0dc 100644
> --- a/lib/stackdepot.c
> +++ b/lib/stackdepot.c
> @@ -23,6 +23,7 @@
>  #include <linux/jhash.h>
>  #include <linux/kernel.h>
>  #include <linux/mm.h>
> +#include <linux/mutex.h>
>  #include <linux/percpu.h>
>  #include <linux/printk.h>
>  #include <linux/slab.h>
> @@ -145,6 +146,7 @@ depot_alloc_stack(unsigned long *entries, int size, u32 hash, void **prealloc)
>  #define STACK_HASH_MASK (STACK_HASH_SIZE - 1)
>  #define STACK_HASH_SEED 0x9747b28c
>
> +DEFINE_MUTEX(stack_depot_init_mutex);
>  static bool stack_depot_disable;
>  static struct stack_record **stack_table;
>
> @@ -161,18 +163,38 @@ static int __init is_stack_depot_disabled(char *str)
>  }
>  early_param("stack_depot_disable", is_stack_depot_disabled);
>
> -int __init stack_depot_init(void)
> +/*
> + * __ref because of memblock_alloc(), which will not be actually called after
> + * the __init code is gone
> + */
> +__ref int stack_depot_init(void)
>  {
> -       if (!stack_depot_disable) {
> +       mutex_lock(&stack_depot_init_mutex);
> +       if (!stack_depot_disable && stack_table == NULL) {
>                 size_t size = (STACK_HASH_SIZE * sizeof(struct stack_record *));
>                 int i;
>
> -               stack_table = memblock_alloc(size, size);
> -               for (i = 0; i < STACK_HASH_SIZE;  i++)
> -                       stack_table[i] = NULL;
> +               if (slab_is_available()) {
> +                       pr_info("Stack Depot allocating hash table with kvmalloc\n");
> +                       stack_table = kvmalloc(size, GFP_KERNEL);
> +               } else {
> +                       pr_info("Stack Depot allocating hash table with memblock_alloc\n");
> +                       stack_table = memblock_alloc(size, SMP_CACHE_BYTES);
> +               }
> +               if (stack_table) {
> +                       for (i = 0; i < STACK_HASH_SIZE;  i++)
> +                               stack_table[i] = NULL;
> +               } else {
> +                       pr_err("Stack Depot failed hash table allocationg, disabling\n");
> +                       stack_depot_disable = true;
> +                       mutex_unlock(&stack_depot_init_mutex);
> +                       return -ENOMEM;
> +               }
>         }
> +       mutex_unlock(&stack_depot_init_mutex);
>         return 0;
>  }
> +EXPORT_SYMBOL_GPL(stack_depot_init);
>
>  /* Calculate hash for a stack */
>  static inline u32 hash_stack(unsigned long *entries, unsigned int size)
> diff --git a/mm/page_owner.c b/mm/page_owner.c
> index a83f546c06b5..a48607b51a97 100644
> --- a/mm/page_owner.c
> +++ b/mm/page_owner.c
> @@ -80,6 +80,8 @@ static void init_page_owner(void)
>         if (!page_owner_enabled)
>                 return;
>
> +       stack_depot_init();
> +
>         register_dummy_stack();
>         register_failure_stack();
>         register_early_stack();
> --
> 2.33.0
>
> --
> You received this message because you are subscribed to the Google Groups "kasan-dev" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to kasan-dev+unsubscribe@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/20211007095815.3563-1-vbabka%40suse.cz.

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH] lib/stackdepot: allow optional init and stack_table allocation by kvmalloc()
  2021-10-07  9:58 [PATCH] lib/stackdepot: allow optional init and stack_table allocation by kvmalloc() Vlastimil Babka
  2021-10-07 11:01 ` Dmitry Vyukov
@ 2021-10-07 11:01 ` Marco Elver
  2021-10-11 17:02   ` Vlastimil Babka
  1 sibling, 1 reply; 6+ messages in thread
From: Marco Elver @ 2021-10-07 11:01 UTC (permalink / raw)
  To: Vlastimil Babka
  Cc: Andrew Morton, linux-mm, linux-kernel, dri-devel, intel-gfx,
	kasan-dev, Vijayanand Jitta, Maarten Lankhorst, Maxime Ripard,
	Thomas Zimmermann, David Airlie, Daniel Vetter, Andrey Ryabinin,
	Alexander Potapenko, Andrey Konovalov, Dmitry Vyukov,
	Geert Uytterhoeven, Oliver Glitta, Imran Khan

On Thu, Oct 07, 2021 at 11:58AM +0200, Vlastimil Babka wrote:
[...] 
> - Add a CONFIG_STACKDEPOT_ALWAYS_INIT flag to keep using the current
>   well-defined point of allocation as part of mem_init(). Make CONFIG_KASAN
>   select this flag.
> - Other users have to call stack_depot_init() as part of their own init when
>   it's determined that stack depot will actually be used. This may depend on
>   both config and runtime conditions. Convert current users which are
>   page_owner and several in the DRM subsystem. Same will be done for SLUB
>   later.
> - Because the init might now be called after the boot-time memblock allocation
>   has given all memory to the buddy allocator, change stack_depot_init() to
>   allocate stack_table with kvmalloc() when memblock is no longer available.
>   Also handle allocation failure by disabling stackdepot (could have
>   theoretically happened even with memblock allocation previously), and don't
>   unnecessarily align the memblock allocation to its own size anymore.
...
> Hi, I'd appreciate review of the DRM parts - namely that I've got correctly
> that stack_depot_init() is called from the proper init functions and iff
> stack_depot_save() is going to be used later. Thanks!

For ease of review between stackdepot and DRM changes, I thought it'd be
nice to split into 2 patches, but not sure it'll work, because you're
changing the semantics of the normal STACKDEPOT.

One option would be to flip it around, and instead have
STACKDEPOT_LAZY_INIT, but that seems counter-intuitive if the majority
of STACKDEPOT users are LAZY_INIT users.

On the other hand, the lazy initialization mode you're introducing
requires an explicit stack_depot_init() call somewhere and isn't as
straightforward as before.

Not sure what is best. My intuition tells me STACKDEPOT_LAZY_INIT would
be safer as it's a deliberate opt-in to the lazy initialization
behaviour.

Preferences?

[...]
> --- a/drivers/gpu/drm/drm_mm.c
> +++ b/drivers/gpu/drm/drm_mm.c
> @@ -980,6 +980,10 @@ void drm_mm_init(struct drm_mm *mm, u64 start, u64 size)
>  	add_hole(&mm->head_node);
>  
>  	mm->scan_active = 0;
> +
> +#ifdef CONFIG_DRM_DEBUG_MM
> +	stack_depot_init();
> +#endif

DRM_DEBUG_MM implies STACKDEPOT. Not sure what is more readable to drm
maintainers, but perhaps it'd be nicer to avoid the #ifdef here, and
instead just keep the no-op version of stack_depot_init() in
<linux/stackdepot.h>. I don't have a strong preference.

>  }
>  EXPORT_SYMBOL(drm_mm_init);
>  
> diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
> index 0d85f3c5c526..806c32ab410b 100644
> --- a/drivers/gpu/drm/i915/intel_runtime_pm.c
> +++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
> @@ -68,6 +68,9 @@ static noinline depot_stack_handle_t __save_depot_stack(void)
>  static void init_intel_runtime_pm_wakeref(struct intel_runtime_pm *rpm)
>  {
>  	spin_lock_init(&rpm->debug.lock);
> +
> +	if (rpm->available)
> +		stack_depot_init();
>  }
>  
>  static noinline depot_stack_handle_t
> diff --git a/include/linux/stackdepot.h b/include/linux/stackdepot.h
> index c34b55a6e554..60ba99a43745 100644
> --- a/include/linux/stackdepot.h
> +++ b/include/linux/stackdepot.h
> @@ -15,6 +15,16 @@
>  
>  typedef u32 depot_stack_handle_t;
>  
> +/*
> + * Every user of stack depot has to call this during its own init when it's
> + * decided that it will be calling stack_depot_save() later.
> + *
> + * The alternative is to select STACKDEPOT_ALWAYS_INIT to have stack depot
> + * enabled as part of mm_init(), for subsystems where it's known at compile time
> + * that stack depot will be used.
> + */
> +int stack_depot_init(void);
> +
>  depot_stack_handle_t __stack_depot_save(unsigned long *entries,
>  					unsigned int nr_entries,
>  					gfp_t gfp_flags, bool can_alloc);
> @@ -30,13 +40,4 @@ int stack_depot_snprint(depot_stack_handle_t handle, char *buf, size_t size,
>  
>  void stack_depot_print(depot_stack_handle_t stack);
>  
> -#ifdef CONFIG_STACKDEPOT
> -int stack_depot_init(void);
> -#else
> -static inline int stack_depot_init(void)
> -{
> -	return 0;
> -}
> -#endif	/* CONFIG_STACKDEPOT */
> -

Could we avoid the IS_ENABLED() in init/main.c by adding a wrapper here:

+#ifdef CONFIG_STACKDEPOT_ALWAYS_INIT
+static inline int stack_depot_early_init(void)	{ return stack_depot_init(); }
+#else
+static inline int stack_depot_early_init(void)	{ return 0; }
+#endif	/* CONFIG_STACKDEPOT_ALWAYS_INIT */

>  #endif
> diff --git a/init/main.c b/init/main.c
> index ee4d3e1b3eb9..b6a5833d98f5 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -844,7 +844,8 @@ static void __init mm_init(void)
>  	init_mem_debugging_and_hardening();
>  	kfence_alloc_pool();
>  	report_meminit();
> -	stack_depot_init();
> +	if (IS_ENABLED(CONFIG_STACKDEPOT_ALWAYS_INIT))
> +		stack_depot_init();

I'd push the decision of when to call this into <linux/stackdepot.h> via
wrapper stack_depot_early_init().

>  	mem_init();
>  	mem_init_print_info();
>  	/* page_owner must be initialized after buddy is ready */
> diff --git a/lib/Kconfig b/lib/Kconfig
> index 5e7165e6a346..df6bcf0a4cc3 100644
> --- a/lib/Kconfig
> +++ b/lib/Kconfig
> @@ -671,6 +671,9 @@ config STACKDEPOT
>  	bool
>  	select STACKTRACE
>  
> +config STACKDEPOT_ALWAYS_INIT
> +	bool

It looks like every users of STACKDEPOT_ALWAYS_INIT will also select
STACKDEPOT, so we could just make this:

+config STACKDEPOT_ALWAYS_INIT
+	bool
+	select STACKDEPOT

And remove the redundant 'select STACKDEPOT' in Kconfig.kasan.

>  config STACK_HASH_ORDER
>  	int "stack depot hash size (12 => 4KB, 20 => 1024KB)"
>  	range 12 20
> diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
> index cdc842d090db..695deb603c66 100644
> --- a/lib/Kconfig.kasan
> +++ b/lib/Kconfig.kasan
> @@ -39,6 +39,7 @@ menuconfig KASAN
>  		   HAVE_ARCH_KASAN_HW_TAGS
>  	depends on (SLUB && SYSFS) || (SLAB && !DEBUG_SLAB)
>  	select STACKDEPOT
> +	select STACKDEPOT_ALWAYS_INIT

[...]
>  
> -int __init stack_depot_init(void)
> +/*
> + * __ref because of memblock_alloc(), which will not be actually called after
> + * the __init code is gone

The reason is that after __init code is gone, slab_is_available() will
be true (might be worth adding to the comment).

> + */
> +__ref int stack_depot_init(void)
>  {
> -	if (!stack_depot_disable) {
> +	mutex_lock(&stack_depot_init_mutex);
> +	if (!stack_depot_disable && stack_table == NULL) {
>  		size_t size = (STACK_HASH_SIZE * sizeof(struct stack_record *));

Thanks,
-- Marco

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH] lib/stackdepot: allow optional init and stack_table allocation by kvmalloc()
  2021-10-07 11:01 ` Marco Elver
@ 2021-10-11 17:02   ` Vlastimil Babka
  2021-10-11 17:08     ` Marco Elver
  0 siblings, 1 reply; 6+ messages in thread
From: Vlastimil Babka @ 2021-10-11 17:02 UTC (permalink / raw)
  To: Marco Elver
  Cc: Andrew Morton, linux-mm, linux-kernel, dri-devel, intel-gfx,
	kasan-dev, Vijayanand Jitta, Maarten Lankhorst, Maxime Ripard,
	Thomas Zimmermann, David Airlie, Daniel Vetter, Andrey Ryabinin,
	Alexander Potapenko, Andrey Konovalov, Dmitry Vyukov,
	Geert Uytterhoeven, Oliver Glitta, Imran Khan

On 10/7/21 13:01, Marco Elver wrote:
> On Thu, Oct 07, 2021 at 11:58AM +0200, Vlastimil Babka wrote:
> [...] 
>> - Add a CONFIG_STACKDEPOT_ALWAYS_INIT flag to keep using the current
>>   well-defined point of allocation as part of mem_init(). Make CONFIG_KASAN
>>   select this flag.
>> - Other users have to call stack_depot_init() as part of their own init when
>>   it's determined that stack depot will actually be used. This may depend on
>>   both config and runtime conditions. Convert current users which are
>>   page_owner and several in the DRM subsystem. Same will be done for SLUB
>>   later.
>> - Because the init might now be called after the boot-time memblock allocation
>>   has given all memory to the buddy allocator, change stack_depot_init() to
>>   allocate stack_table with kvmalloc() when memblock is no longer available.
>>   Also handle allocation failure by disabling stackdepot (could have
>>   theoretically happened even with memblock allocation previously), and don't
>>   unnecessarily align the memblock allocation to its own size anymore.
> ...
>> Hi, I'd appreciate review of the DRM parts - namely that I've got correctly
>> that stack_depot_init() is called from the proper init functions and iff
>> stack_depot_save() is going to be used later. Thanks!
> 
> For ease of review between stackdepot and DRM changes, I thought it'd be
> nice to split into 2 patches, but not sure it'll work, because you're
> changing the semantics of the normal STACKDEPOT.

Yeah, that's why it's a single patch. As the DRM parts are clearly separated
to their files, I think review should be fine.

> One option would be to flip it around, and instead have
> STACKDEPOT_LAZY_INIT, but that seems counter-intuitive if the majority
> of STACKDEPOT users are LAZY_INIT users.

Agree.

> On the other hand, the lazy initialization mode you're introducing
> requires an explicit stack_depot_init() call somewhere and isn't as
> straightforward as before.
> 
> Not sure what is best. My intuition tells me STACKDEPOT_LAZY_INIT would
> be safer as it's a deliberate opt-in to the lazy initialization
> behaviour.

I think it should be fine with ALWAYS_INIT. There are not many stackdepot
users being added, and anyone developing a new one will very quickly find
out if they forget to call stack_depot_init()?

> Preferences?
> 
> [...]
>> --- a/drivers/gpu/drm/drm_mm.c
>> +++ b/drivers/gpu/drm/drm_mm.c
>> @@ -980,6 +980,10 @@ void drm_mm_init(struct drm_mm *mm, u64 start, u64 size)
>>  	add_hole(&mm->head_node);
>>  
>>  	mm->scan_active = 0;
>> +
>> +#ifdef CONFIG_DRM_DEBUG_MM
>> +	stack_depot_init();
>> +#endif
> 
> DRM_DEBUG_MM implies STACKDEPOT. Not sure what is more readable to drm
> maintainers, but perhaps it'd be nicer to avoid the #ifdef here, and
> instead just keep the no-op version of stack_depot_init() in
> <linux/stackdepot.h>. I don't have a strong preference.

Hm, but in case STACKDEPOT is also selected by something else (e.g.
CONFIG_PAGE_OWNER) which uses lazy init but isn't enabled on boot, then
without #ifdef CONFIG_DRM_DEBUG_MM above, this code would call a
stack_depot_init() (that's not a no-op) even in case it's not going to be
using it, so not what we want to achieve.
But it could be changed to use IS_ENABLED() if that's preferred by DRM folks.

BTW it's possible that there won't be any DRM review because this failed to
apply:
https://patchwork.freedesktop.org/series/95549/
DRM folks, any hint how to indicate that the base was next-20211001?

>> @@ -30,13 +40,4 @@ int stack_depot_snprint(depot_stack_handle_t handle, char *buf, size_t size,
>>  
>>  void stack_depot_print(depot_stack_handle_t stack);
>>  
>> -#ifdef CONFIG_STACKDEPOT
>> -int stack_depot_init(void);
>> -#else
>> -static inline int stack_depot_init(void)
>> -{
>> -	return 0;
>> -}
>> -#endif	/* CONFIG_STACKDEPOT */
>> -
> 
> Could we avoid the IS_ENABLED() in init/main.c by adding a wrapper here:
> 
> +#ifdef CONFIG_STACKDEPOT_ALWAYS_INIT
> +static inline int stack_depot_early_init(void)	{ return stack_depot_init(); }
> +#else
> +static inline int stack_depot_early_init(void)	{ return 0; }
> +#endif	/* CONFIG_STACKDEPOT_ALWAYS_INIT */

We could, but it's a wrapper made for only a single caller...

>>  #endif
>> diff --git a/init/main.c b/init/main.c
>> index ee4d3e1b3eb9..b6a5833d98f5 100644
>> --- a/init/main.c
>> +++ b/init/main.c
>> @@ -844,7 +844,8 @@ static void __init mm_init(void)
>>  	init_mem_debugging_and_hardening();
>>  	kfence_alloc_pool();
>>  	report_meminit();
>> -	stack_depot_init();
>> +	if (IS_ENABLED(CONFIG_STACKDEPOT_ALWAYS_INIT))
>> +		stack_depot_init();
> 
> I'd push the decision of when to call this into <linux/stackdepot.h> via
> wrapper stack_depot_early_init().

No strong preferrences, if you think it's worth it.

>>  	mem_init();
>>  	mem_init_print_info();
>>  	/* page_owner must be initialized after buddy is ready */
>> diff --git a/lib/Kconfig b/lib/Kconfig
>> index 5e7165e6a346..df6bcf0a4cc3 100644
>> --- a/lib/Kconfig
>> +++ b/lib/Kconfig
>> @@ -671,6 +671,9 @@ config STACKDEPOT
>>  	bool
>>  	select STACKTRACE
>>  
>> +config STACKDEPOT_ALWAYS_INIT
>> +	bool
> 
> It looks like every users of STACKDEPOT_ALWAYS_INIT will also select
> STACKDEPOT, so we could just make this:
> 
> +config STACKDEPOT_ALWAYS_INIT
> +	bool
> +	select STACKDEPOT
> 
> And remove the redundant 'select STACKDEPOT' in Kconfig.kasan.

Right, will do, if KConfig resolver doesn't bite me.

>>  config STACK_HASH_ORDER
>>  	int "stack depot hash size (12 => 4KB, 20 => 1024KB)"
>>  	range 12 20
>> diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
>> index cdc842d090db..695deb603c66 100644
>> --- a/lib/Kconfig.kasan
>> +++ b/lib/Kconfig.kasan
>> @@ -39,6 +39,7 @@ menuconfig KASAN
>>  		   HAVE_ARCH_KASAN_HW_TAGS
>>  	depends on (SLUB && SYSFS) || (SLAB && !DEBUG_SLAB)
>>  	select STACKDEPOT
>> +	select STACKDEPOT_ALWAYS_INIT
> 
> [...]
>>  
>> -int __init stack_depot_init(void)
>> +/*
>> + * __ref because of memblock_alloc(), which will not be actually called after
>> + * the __init code is gone
> 
> The reason is that after __init code is gone, slab_is_available() will
> be true (might be worth adding to the comment).

OK

Thanks for the review!

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH] lib/stackdepot: allow optional init and stack_table allocation by kvmalloc()
  2021-10-11 17:02   ` Vlastimil Babka
@ 2021-10-11 17:08     ` Marco Elver
  2021-10-12  8:31       ` Vlastimil Babka
  0 siblings, 1 reply; 6+ messages in thread
From: Marco Elver @ 2021-10-11 17:08 UTC (permalink / raw)
  To: Vlastimil Babka
  Cc: Andrew Morton, linux-mm, linux-kernel, dri-devel, intel-gfx,
	kasan-dev, Vijayanand Jitta, Maarten Lankhorst, Maxime Ripard,
	Thomas Zimmermann, David Airlie, Daniel Vetter, Andrey Ryabinin,
	Alexander Potapenko, Andrey Konovalov, Dmitry Vyukov,
	Geert Uytterhoeven, Oliver Glitta, Imran Khan

On Mon, 11 Oct 2021 at 19:02, Vlastimil Babka <vbabka@suse.cz> wrote:
[...]
> > On the other hand, the lazy initialization mode you're introducing
> > requires an explicit stack_depot_init() call somewhere and isn't as
> > straightforward as before.
> >
> > Not sure what is best. My intuition tells me STACKDEPOT_LAZY_INIT would
> > be safer as it's a deliberate opt-in to the lazy initialization
> > behaviour.
>
> I think it should be fine with ALWAYS_INIT. There are not many stackdepot
> users being added, and anyone developing a new one will very quickly find
> out if they forget to call stack_depot_init()?

I think that's fine.

> > Preferences?
> >
> > [...]
> >> --- a/drivers/gpu/drm/drm_mm.c
> >> +++ b/drivers/gpu/drm/drm_mm.c
> >> @@ -980,6 +980,10 @@ void drm_mm_init(struct drm_mm *mm, u64 start, u64 size)
> >>      add_hole(&mm->head_node);
> >>
> >>      mm->scan_active = 0;
> >> +
> >> +#ifdef CONFIG_DRM_DEBUG_MM
> >> +    stack_depot_init();
> >> +#endif
> >
> > DRM_DEBUG_MM implies STACKDEPOT. Not sure what is more readable to drm
> > maintainers, but perhaps it'd be nicer to avoid the #ifdef here, and
> > instead just keep the no-op version of stack_depot_init() in
> > <linux/stackdepot.h>. I don't have a strong preference.
>
> Hm, but in case STACKDEPOT is also selected by something else (e.g.
> CONFIG_PAGE_OWNER) which uses lazy init but isn't enabled on boot, then
> without #ifdef CONFIG_DRM_DEBUG_MM above, this code would call a
> stack_depot_init() (that's not a no-op) even in case it's not going to be
> using it, so not what we want to achieve.
> But it could be changed to use IS_ENABLED() if that's preferred by DRM folks.

You're right -- but I'll leave this to DRM folks.

> BTW it's possible that there won't be any DRM review because this failed to
> apply:
> https://patchwork.freedesktop.org/series/95549/
> DRM folks, any hint how to indicate that the base was next-20211001?
>
[...]
> > +#ifdef CONFIG_STACKDEPOT_ALWAYS_INIT
> > +static inline int stack_depot_early_init(void)       { return stack_depot_init(); }
> > +#else
> > +static inline int stack_depot_early_init(void)       { return 0; }
> > +#endif       /* CONFIG_STACKDEPOT_ALWAYS_INIT */
>
> We could, but it's a wrapper made for only a single caller...
>
> >>  #endif
> >> diff --git a/init/main.c b/init/main.c
> >> index ee4d3e1b3eb9..b6a5833d98f5 100644
> >> --- a/init/main.c
> >> +++ b/init/main.c
> >> @@ -844,7 +844,8 @@ static void __init mm_init(void)
> >>      init_mem_debugging_and_hardening();
> >>      kfence_alloc_pool();
> >>      report_meminit();
> >> -    stack_depot_init();
> >> +    if (IS_ENABLED(CONFIG_STACKDEPOT_ALWAYS_INIT))
> >> +            stack_depot_init();
> >
> > I'd push the decision of when to call this into <linux/stackdepot.h> via
> > wrapper stack_depot_early_init().
>
> No strong preferrences, if you think it's worth it.

All the other *init() functions seem to follow the same idiom as there
are barely any IS_ENABLED() in init/main.c.  So I think it's just
about being consistent with the rest.

Thanks,
-- Marco

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH] lib/stackdepot: allow optional init and stack_table allocation by kvmalloc()
  2021-10-11 17:08     ` Marco Elver
@ 2021-10-12  8:31       ` Vlastimil Babka
  0 siblings, 0 replies; 6+ messages in thread
From: Vlastimil Babka @ 2021-10-12  8:31 UTC (permalink / raw)
  To: Marco Elver
  Cc: Andrew Morton, linux-mm, linux-kernel, dri-devel, intel-gfx,
	kasan-dev, Vijayanand Jitta, Maarten Lankhorst, Maxime Ripard,
	Thomas Zimmermann, David Airlie, Daniel Vetter, Andrey Ryabinin,
	Alexander Potapenko, Andrey Konovalov, Dmitry Vyukov,
	Geert Uytterhoeven, Oliver Glitta, Imran Khan

On 10/11/21 19:08, Marco Elver wrote:
> On Mon, 11 Oct 2021 at 19:02, Vlastimil Babka <vbabka@suse.cz> wrote:
> [...]
>> > On the other hand, the lazy initialization mode you're introducing
>> > requires an explicit stack_depot_init() call somewhere and isn't as
>> > straightforward as before.
>> >
>> > Not sure what is best. My intuition tells me STACKDEPOT_LAZY_INIT would
>> > be safer as it's a deliberate opt-in to the lazy initialization
>> > behaviour.
>>
>> I think it should be fine with ALWAYS_INIT. There are not many stackdepot
>> users being added, and anyone developing a new one will very quickly find
>> out if they forget to call stack_depot_init()?
> 
> I think that's fine.
> 
>> > Preferences?
>> >
>> > [...]
>> >> --- a/drivers/gpu/drm/drm_mm.c
>> >> +++ b/drivers/gpu/drm/drm_mm.c
>> >> @@ -980,6 +980,10 @@ void drm_mm_init(struct drm_mm *mm, u64 start, u64 size)
>> >>      add_hole(&mm->head_node);
>> >>
>> >>      mm->scan_active = 0;
>> >> +
>> >> +#ifdef CONFIG_DRM_DEBUG_MM
>> >> +    stack_depot_init();
>> >> +#endif
>> >
>> > DRM_DEBUG_MM implies STACKDEPOT. Not sure what is more readable to drm
>> > maintainers, but perhaps it'd be nicer to avoid the #ifdef here, and
>> > instead just keep the no-op version of stack_depot_init() in
>> > <linux/stackdepot.h>. I don't have a strong preference.
>>
>> Hm, but in case STACKDEPOT is also selected by something else (e.g.
>> CONFIG_PAGE_OWNER) which uses lazy init but isn't enabled on boot, then
>> without #ifdef CONFIG_DRM_DEBUG_MM above, this code would call a
>> stack_depot_init() (that's not a no-op) even in case it's not going to be
>> using it, so not what we want to achieve.
>> But it could be changed to use IS_ENABLED() if that's preferred by DRM folks.
> 
> You're right -- but I'll leave this to DRM folks.

Ah, the file only includes stackdepot.h in a #ifdef CONFIG_DRM_DEBUG_MM
section so I will keep the #ifdef here for a minimal change, unless
requested otherwise.

^ permalink raw reply	[flat|nested] 6+ messages in thread

end of thread, other threads:[~2021-10-12  8:31 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2021-10-07  9:58 [PATCH] lib/stackdepot: allow optional init and stack_table allocation by kvmalloc() Vlastimil Babka
2021-10-07 11:01 ` Dmitry Vyukov
2021-10-07 11:01 ` Marco Elver
2021-10-11 17:02   ` Vlastimil Babka
2021-10-11 17:08     ` Marco Elver
2021-10-12  8:31       ` Vlastimil Babka

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