[patch 021/262] lib/stackdepot: introduce __stack_depot_save()

Andrew Morton
2021-11-05T20:35:43Z

From: Marco Elver <elver@google.com>
Subject: lib/stackdepot: introduce __stack_depot_save()

Add __stack_depot_save(), which provides more fine-grained control over
stackdepot's memory allocation behaviour, in case stackdepot runs out of
"stack slabs".

Normally stackdepot uses alloc_pages() in case it runs out of space;
passing can_alloc==false to __stack_depot_save() prohibits this, at the
cost of more likely failure to record a stack trace.

Link: https://lkml.kernel.org/r/20210913112609.2651084-4-elver@google.com
Signed-off-by: Marco Elver <elver@google.com>
Tested-by: Shuah Khan <skhan@linuxfoundation.org>
Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Taras Madan <tarasmadan@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vijayanand Jitta <vjitta@codeaurora.org>
Cc: Vinayak Menon <vinmenon@codeaurora.org>
Cc: Walter Wu <walter-zh.wu@mediatek.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

include/linux/stackdepot.h | 4 +++
lib/stackdepot.c | 43 ++++++++++++++++++++++++++++++-----
2 files changed, 41 insertions(+), 6 deletions(-)

--- a/include/linux/stackdepot.h~lib-stackdepot-introduce-__stack_depot_save
+++ a/include/linux/stackdepot.h
@@ -15,6 +15,10 @@

typedef u32 depot_stack_handle_t;

+depot_stack_handle_t __stack_depot_save(unsigned long *entries,
+ unsigned int nr_entries,
+ gfp_t gfp_flags, bool can_alloc);
+
depot_stack_handle_t stack_depot_save(unsigned long *entries,
unsigned int nr_entries, gfp_t gfp_flags);

--- a/lib/stackdepot.c~lib-stackdepot-introduce-__stack_depot_save
+++ a/lib/stackdepot.c
@@ -248,17 +248,28 @@ unsigned int stack_depot_fetch(depot_sta
EXPORT_SYMBOL_GPL(stack_depot_fetch);

/**
- * stack_depot_save - Save a stack trace from an array
+ * __stack_depot_save - Save a stack trace from an array
*
* @entries: Pointer to storage array
* @nr_entries: Size of the storage array
* @alloc_flags: Allocation gfp flags
+ * @can_alloc: Allocate stack slabs (increased chance of failure if false)
+ *
+ * Saves a stack trace from @entries array of size @nr_entries. If @can_alloc is
+ * %true, is allowed to replenish the stack slab pool in case no space is left
+ * (allocates using GFP flags of @alloc_flags). If @can_alloc is %false, avoids
+ * any allocations and will fail if no space is left to store the stack trace.
+ *
+ * Context: Any context, but setting @can_alloc to %false is required if
+ * alloc_pages() cannot be used from the current context. Currently
+ * this is the case from contexts where neither %GFP_ATOMIC nor
+ * %GFP_NOWAIT can be used (NMI, raw_spin_lock).
*
- * Return: The handle of the stack struct stored in depot
+ * Return: The handle of the stack struct stored in depot, 0 on failure.
*/
-depot_stack_handle_t stack_depot_save(unsigned long *entries,
- unsigned int nr_entries,
- gfp_t alloc_flags)
+depot_stack_handle_t __stack_depot_save(unsigned long *entries,
+ unsigned int nr_entries,
+ gfp_t alloc_flags, bool can_alloc)
{
struct stack_record *found = NULL, **bucket;
depot_stack_handle_t retval = 0;
@@ -291,7 +302,7 @@ depot_stack_handle_t stack_depot_save(un
* The smp_load_acquire() here pairs with smp_store_release() to
* |next_slab_inited| in depot_alloc_stack() and init_stack_slab().
*/
- if (unlikely(!smp_load_acquire(&next_slab_inited))) {
+ if (unlikely(can_alloc && !smp_load_acquire(&next_slab_inited))) {
/*
* Zero out zone modifiers, as we don't have specific zone
* requirements. Keep the flags related to allocation in atomic
@@ -339,6 +350,26 @@ exit:
fast_exit:
return retval;
}
+EXPORT_SYMBOL_GPL(__stack_depot_save);
+
+/**
+ * stack_depot_save - Save a stack trace from an array
+ *
+ * @entries: Pointer to storage array
+ * @nr_entries: Size of the storage array
+ * @alloc_flags: Allocation gfp flags
+ *
+ * Context: Contexts where allocations via alloc_pages() are allowed.
+ * See __stack_depot_save() for more details.
+ *
+ * Return: The handle of the stack struct stored in depot, 0 on failure.
+ */
+depot_stack_handle_t stack_depot_save(unsigned long *entries,
+ unsigned int nr_entries,
+ gfp_t alloc_flags)
+{
+ return __stack_depot_save(entries, nr_entries, alloc_flags, true);
+}
EXPORT_SYMBOL_GPL(stack_depot_save);

static inline int in_irqentry_text(unsigned long ptr)
_