Commit cd0fc64e authored by Andrey Konovalov's avatar Andrey Konovalov Committed by Andrew Morton
Browse files

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: default avatarAndrey Konovalov <andreyknvl@google.com>
Reviewed-by: default avatarAlexander Potapenko <glider@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 514d5c55

lib/stackdepot.c

+24 −10
Original line number Diff line number Diff line
@@ -218,32 +218,39 @@ int stack_depot_init(void) 
}

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;