From cd0fc64e76844758b78d0fd376ae3ca4fd802049 Mon Sep 17 00:00:00 2001 From: Andrey Konovalov Date: Fri, 10 Feb 2023 22:16:01 +0100 Subject: [PATCH] lib/stackdepot: annotate depot_init_pool and depot_alloc_stack Clean up the exisiting comments and add new ones to depot_init_pool and depot_alloc_stack. As a part of the clean-up, remove mentions of which variable is accessed by smp_store_release and smp_load_acquire: it is clear as is from the code. Link: https://lkml.kernel.org/r/f80b02951364e6b40deda965b4003de0cd1a532d.1676063693.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov Reviewed-by: Alexander Potapenko Signed-off-by: Andrew Morton --- lib/stackdepot.c | 34 ++++++++++++++++++++++++---------- 1 file changed, 24 insertions(+), 10 deletions(-) diff --git a/lib/stackdepot.c b/lib/stackdepot.c index d4d9882..c4bc198 100644 --- a/lib/stackdepot.c +++ b/lib/stackdepot.c @@ -218,32 +218,39 @@ out_unlock: } EXPORT_SYMBOL_GPL(stack_depot_init); +/* Uses preallocated memory to initialize a new stack depot pool. */ static void depot_init_pool(void **prealloc) { /* - * This smp_load_acquire() pairs with smp_store_release() to - * |next_pool_inited| below and in depot_alloc_stack(). + * smp_load_acquire() here pairs with smp_store_release() below and + * in depot_alloc_stack(). */ if (smp_load_acquire(&next_pool_inited)) return; + + /* Check if the current pool is not yet allocated. */ if (stack_pools[pool_index] == NULL) { + /* Use the preallocated memory for the current pool. */ stack_pools[pool_index] = *prealloc; *prealloc = NULL; } else { - /* If this is the last depot pool, do not touch the next one. */ + /* + * Otherwise, use the preallocated memory for the next pool + * as long as we do not exceed the maximum number of pools. + */ if (pool_index + 1 < DEPOT_MAX_POOLS) { stack_pools[pool_index + 1] = *prealloc; *prealloc = NULL; } /* - * This smp_store_release pairs with smp_load_acquire() from - * |next_pool_inited| above and in stack_depot_save(). + * This smp_store_release pairs with smp_load_acquire() above + * and in stack_depot_save(). */ smp_store_release(&next_pool_inited, 1); } } -/* Allocation of a new stack in raw storage */ +/* Allocates a new stack in a stack depot pool. */ static struct stack_record * depot_alloc_stack(unsigned long *entries, int size, u32 hash, void **prealloc) { @@ -252,28 +259,35 @@ depot_alloc_stack(unsigned long *entries, int size, u32 hash, void **prealloc) required_size = ALIGN(required_size, 1 << DEPOT_STACK_ALIGN); + /* Check if there is not enough space in the current pool. */ if (unlikely(pool_offset + required_size > DEPOT_POOL_SIZE)) { + /* Bail out if we reached the pool limit. */ if (unlikely(pool_index + 1 >= DEPOT_MAX_POOLS)) { WARN_ONCE(1, "Stack depot reached limit capacity"); return NULL; } + + /* Move on to the next pool. */ pool_index++; pool_offset = 0; /* - * smp_store_release() here pairs with smp_load_acquire() from - * |next_pool_inited| in stack_depot_save() and - * depot_init_pool(). + * smp_store_release() here pairs with smp_load_acquire() in + * stack_depot_save() and depot_init_pool(). */ if (pool_index + 1 < DEPOT_MAX_POOLS) smp_store_release(&next_pool_inited, 0); } + + /* Assign the preallocated memory to a pool if required. */ if (*prealloc) depot_init_pool(prealloc); + + /* Check if we have a pool to save the stack trace. */ if (stack_pools[pool_index] == NULL) return NULL; + /* Save the stack trace. */ stack = stack_pools[pool_index] + pool_offset; - stack->hash = hash; stack->size = size; stack->handle.pool_index = pool_index; -- 2.7.4