From fcccc41ecb0c96e59c471c389cd708014be2efc8 Mon Sep 17 00:00:00 2001 From: Andrey Konovalov Date: Mon, 20 Nov 2023 18:47:05 +0100 Subject: lib/stackdepot: fix and clean-up atomic annotations Drop smp_load_acquire from next_pool_required in depot_init_pool, as both depot_init_pool and the all smp_store_release's to this variable are executed under the stack depot lock. Also simplify and clean up comments accompanying the use of atomic accesses in the stack depot code. Link: https://lkml.kernel.org/r/c118ef044d8db80248d9e1f14592c72e8429e9d9.1700502145.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov Reviewed-by: Alexander Potapenko Cc: Dmitry Vyukov Cc: Evgenii Stepanov Cc: Marco Elver Cc: Oscar Salvador Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- lib/stackdepot.c | 29 ++++++++++++++--------------- 1 file changed, 14 insertions(+), 15 deletions(-) (limited to 'lib/stackdepot.c') diff --git a/lib/stackdepot.c b/lib/stackdepot.c index 682497dbe081..cfa3c6c7cc2e 100644 --- a/lib/stackdepot.c +++ b/lib/stackdepot.c @@ -231,10 +231,10 @@ static void depot_init_pool(void **prealloc) /* * If the next pool is already initialized or the maximum number of * pools is reached, do not use the preallocated memory. - * smp_load_acquire() here pairs with smp_store_release() below and - * in depot_alloc_stack(). + * Access next_pool_required non-atomically, as there are no concurrent + * write accesses to this variable. */ - if (!smp_load_acquire(&next_pool_required)) + if (!next_pool_required) return; /* Check if the current pool is not yet allocated. */ @@ -255,8 +255,8 @@ static void depot_init_pool(void **prealloc) * At this point, either the next pool is initialized or the * maximum number of pools is reached. In either case, take * note that initializing another pool is not required. - * This smp_store_release pairs with smp_load_acquire() above - * and in stack_depot_save(). + * smp_store_release() pairs with smp_load_acquire() in + * stack_depot_save(). */ smp_store_release(&next_pool_required, 0); } @@ -279,7 +279,7 @@ depot_alloc_stack(unsigned long *entries, int size, u32 hash, void **prealloc) /* * Move on to the next pool. - * WRITE_ONCE pairs with potential concurrent read in + * WRITE_ONCE() pairs with potential concurrent read in * stack_depot_fetch(). */ WRITE_ONCE(pool_index, pool_index + 1); @@ -287,8 +287,8 @@ depot_alloc_stack(unsigned long *entries, int size, u32 hash, void **prealloc) /* * If the maximum number of pools is not reached, take note * that the next pool needs to initialized. - * smp_store_release() here pairs with smp_load_acquire() in - * stack_depot_save() and depot_init_pool(). + * smp_store_release() pairs with smp_load_acquire() in + * stack_depot_save(). */ if (pool_index + 1 < DEPOT_MAX_POOLS) smp_store_release(&next_pool_required, 1); @@ -329,7 +329,7 @@ static struct stack_record *depot_fetch_stack(depot_stack_handle_t handle) { union handle_parts parts = { .handle = handle }; /* - * READ_ONCE pairs with potential concurrent write in + * READ_ONCE() pairs with potential concurrent write in * depot_alloc_stack(). */ int pool_index_cached = READ_ONCE(pool_index); @@ -419,8 +419,7 @@ depot_stack_handle_t __stack_depot_save(unsigned long *entries, /* * Fast path: look the stack trace up without locking. - * The smp_load_acquire() here pairs with smp_store_release() to - * |bucket| below. + * smp_load_acquire() pairs with smp_store_release() to |bucket| below. */ found = find_stack(smp_load_acquire(bucket), entries, nr_entries, hash); if (found) @@ -430,8 +429,8 @@ depot_stack_handle_t __stack_depot_save(unsigned long *entries, * Check if another stack pool needs to be initialized. If so, allocate * the memory now - we won't be able to do that under the lock. * - * The smp_load_acquire() here pairs with smp_store_release() to - * |next_pool_inited| in depot_alloc_stack() and depot_init_pool(). + * smp_load_acquire() pairs with smp_store_release() in + * depot_alloc_stack() and depot_init_pool(). */ if (unlikely(can_alloc && smp_load_acquire(&next_pool_required))) { /* @@ -457,8 +456,8 @@ depot_stack_handle_t __stack_depot_save(unsigned long *entries, if (new) { new->next = *bucket; /* - * This smp_store_release() pairs with - * smp_load_acquire() from |bucket| above. + * smp_store_release() pairs with smp_load_acquire() + * from |bucket| above. */ smp_store_release(bucket, new); found = new; -- cgit