diff options
| -rw-r--r-- | drivers/acpi/apei/ghes.c | 60 |
1 files changed, 33 insertions, 27 deletions
diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c index 249cd01cb920..6164bf737ee6 100644 --- a/drivers/acpi/apei/ghes.c +++ b/drivers/acpi/apei/ghes.c @@ -154,7 +154,7 @@ struct ghes_vendor_record_entry { static struct gen_pool *ghes_estatus_pool; static unsigned long ghes_estatus_pool_size_request; -static struct ghes_estatus_cache *ghes_estatus_caches[GHES_ESTATUS_CACHES_SIZE]; +static struct ghes_estatus_cache __rcu *ghes_estatus_caches[GHES_ESTATUS_CACHES_SIZE]; static atomic_t ghes_estatus_cache_alloced; static int ghes_panic_timeout __read_mostly = 30; @@ -789,48 +789,42 @@ static struct ghes_estatus_cache *ghes_estatus_cache_alloc( return cache; } -static void ghes_estatus_cache_free(struct ghes_estatus_cache *cache) +static void ghes_estatus_cache_rcu_free(struct rcu_head *head) { + struct ghes_estatus_cache *cache; u32 len; + cache = container_of(head, struct ghes_estatus_cache, rcu); len = cper_estatus_len(GHES_ESTATUS_FROM_CACHE(cache)); len = GHES_ESTATUS_CACHE_LEN(len); gen_pool_free(ghes_estatus_pool, (unsigned long)cache, len); atomic_dec(&ghes_estatus_cache_alloced); } -static void ghes_estatus_cache_rcu_free(struct rcu_head *head) -{ - struct ghes_estatus_cache *cache; - - cache = container_of(head, struct ghes_estatus_cache, rcu); - ghes_estatus_cache_free(cache); -} - -static void ghes_estatus_cache_add( - struct acpi_hest_generic *generic, - struct acpi_hest_generic_status *estatus) +static void +ghes_estatus_cache_add(struct acpi_hest_generic *generic, + struct acpi_hest_generic_status *estatus) { - int i, slot = -1, count; unsigned long long now, duration, period, max_period = 0; - struct ghes_estatus_cache *cache, *slot_cache = NULL, *new_cache; + struct ghes_estatus_cache *cache, *new_cache; + struct ghes_estatus_cache __rcu *victim; + int i, slot = -1, count; new_cache = ghes_estatus_cache_alloc(generic, estatus); - if (new_cache == NULL) + if (!new_cache) return; + rcu_read_lock(); now = sched_clock(); for (i = 0; i < GHES_ESTATUS_CACHES_SIZE; i++) { cache = rcu_dereference(ghes_estatus_caches[i]); if (cache == NULL) { slot = i; - slot_cache = NULL; break; } duration = now - cache->time_in; if (duration >= GHES_ESTATUS_IN_CACHE_MAX_NSEC) { slot = i; - slot_cache = cache; break; } count = atomic_read(&cache->count); @@ -839,18 +833,30 @@ static void ghes_estatus_cache_add( if (period > max_period) { max_period = period; slot = i; - slot_cache = cache; } } - /* new_cache must be put into array after its contents are written */ - smp_wmb(); - if (slot != -1 && cmpxchg(ghes_estatus_caches + slot, - slot_cache, new_cache) == slot_cache) { - if (slot_cache) - call_rcu(&slot_cache->rcu, ghes_estatus_cache_rcu_free); - } else - ghes_estatus_cache_free(new_cache); rcu_read_unlock(); + + if (slot != -1) { + /* + * Use release semantics to ensure that ghes_estatus_cached() + * running on another CPU will see the updated cache fields if + * it can see the new value of the pointer. + */ + victim = xchg_release(&ghes_estatus_caches[slot], + RCU_INITIALIZER(new_cache)); + + /* + * At this point, victim may point to a cached item different + * from the one based on which we selected the slot. Instead of + * going to the loop again to pick another slot, let's just + * drop the other item anyway: this may cause a false cache + * miss later on, but that won't cause any problems. + */ + if (victim) + call_rcu(&unrcu_pointer(victim)->rcu, + ghes_estatus_cache_rcu_free); + } } static void __ghes_panic(struct ghes *ghes, |