From d765613f04b6aee4ebde71e21c2a6210fe93927d Mon Sep 17 00:00:00 2001 From: Marco Elver Date: Sun, 5 Sep 2021 16:51:26 +0200 Subject: [PATCH 1/4] 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. Signed-off-by: Marco Elver --- include/linux/stackdepot.h | 4 ++++ lib/stackdepot.c | 38 ++++++++++++++++++++++++++++++++------ 2 files changed, 36 insertions(+), 6 deletions(-) diff --git a/include/linux/stackdepot.h b/include/linux/stackdepot.h index 6bb4bc1a5f54..3735b97f62be 100644 --- a/include/linux/stackdepot.h +++ b/include/linux/stackdepot.h @@ -13,6 +13,10 @@ 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); diff --git a/lib/stackdepot.c b/lib/stackdepot.c index c80a9f734253..ec26845b4e29 100644 --- a/lib/stackdepot.c +++ b/lib/stackdepot.c @@ -248,17 +248,26 @@ unsigned int stack_depot_fetch(depot_stack_handle_t handle, 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 + * + * Save a stack trace from an array. If |can_alloc| is false, avoids allocating + * new stack slabs if no space is left in the current stack slab. + * + * 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 not even + * %GFP_ATOMIC or %GFP_NOWAIT can be used (NMI, raw_spin_lock). * * @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) * - * 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 +300,7 @@ depot_stack_handle_t stack_depot_save(unsigned long *entries, * 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 +348,23 @@ depot_stack_handle_t stack_depot_save(unsigned long *entries, 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 + * + * 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) -- 2.33.0.153.gba50c8fa24-goog