diff options
Diffstat (limited to 'mm/percpu.c')
| -rw-r--r-- | mm/percpu.c | 75 |
1 files changed, 35 insertions, 40 deletions
diff --git a/mm/percpu.c b/mm/percpu.c index fe5de97d7caa..e59f7b405bed 100644 --- a/mm/percpu.c +++ b/mm/percpu.c @@ -152,31 +152,12 @@ static struct pcpu_chunk *pcpu_reserved_chunk; static int pcpu_reserved_chunk_limit; /* - * Synchronization rules. - * - * There are two locks - pcpu_alloc_mutex and pcpu_lock. The former - * protects allocation/reclaim paths, chunks, populated bitmap and - * vmalloc mapping. The latter is a spinlock and protects the index - * data structures - chunk slots, chunks and area maps in chunks. - * - * During allocation, pcpu_alloc_mutex is kept locked all the time and - * pcpu_lock is grabbed and released as necessary. All actual memory - * allocations are done using GFP_KERNEL with pcpu_lock released. In - * general, percpu memory can't be allocated with irq off but - * irqsave/restore are still used in alloc path so that it can be used - * from early init path - sched_init() specifically. - * - * Free path accesses and alters only the index data structures, so it - * can be safely called from atomic context. When memory needs to be - * returned to the system, free path schedules reclaim_work which - * grabs both pcpu_alloc_mutex and pcpu_lock, unlinks chunks to be - * reclaimed, release both locks and frees the chunks. Note that it's - * necessary to grab both locks to remove a chunk from circulation as - * allocation path might be referencing the chunk with only - * pcpu_alloc_mutex locked. + * Free path accesses and alters only the index data structures and can be + * safely called from atomic context. When memory needs to be returned to + * the system, free path schedules reclaim_work. */ -static DEFINE_MUTEX(pcpu_alloc_mutex); /* protects whole alloc and reclaim */ -static DEFINE_SPINLOCK(pcpu_lock); /* protects index data structures */ +static DEFINE_SPINLOCK(pcpu_lock); /* all internal data structures */ +static DEFINE_MUTEX(pcpu_alloc_mutex); /* chunk create/destroy, [de]pop */ static struct list_head *pcpu_slot __read_mostly; /* chunk list slots */ @@ -709,7 +690,7 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved) static int warn_limit = 10; struct pcpu_chunk *chunk; const char *err; - int slot, off, new_alloc, cpu; + int slot, off, new_alloc, cpu, ret; int page_start, page_end, rs, re; unsigned long flags; void __percpu *ptr; @@ -729,7 +710,6 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved) return NULL; } - mutex_lock(&pcpu_alloc_mutex); spin_lock_irqsave(&pcpu_lock, flags); /* serve reserved allocations from the reserved chunk if available */ @@ -745,7 +725,7 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved) spin_unlock_irqrestore(&pcpu_lock, flags); if (pcpu_extend_area_map(chunk, new_alloc) < 0) { err = "failed to extend area map of reserved chunk"; - goto fail_unlock_mutex; + goto fail; } spin_lock_irqsave(&pcpu_lock, flags); } @@ -771,7 +751,7 @@ restart: if (pcpu_extend_area_map(chunk, new_alloc) < 0) { err = "failed to extend area map"; - goto fail_unlock_mutex; + goto fail; } spin_lock_irqsave(&pcpu_lock, flags); /* @@ -787,37 +767,53 @@ restart: } } - /* hmmm... no space left, create a new chunk */ spin_unlock_irqrestore(&pcpu_lock, flags); - chunk = pcpu_create_chunk(); - if (!chunk) { - err = "failed to allocate new chunk"; - goto fail_unlock_mutex; + /* + * No space left. Create a new chunk. We don't want multiple + * tasks to create chunks simultaneously. Serialize and create iff + * there's still no empty chunk after grabbing the mutex. + */ + mutex_lock(&pcpu_alloc_mutex); + + if (list_empty(&pcpu_slot[pcpu_nr_slots - 1])) { + chunk = pcpu_create_chunk(); + if (!chunk) { + err = "failed to allocate new chunk"; + goto fail; + } + + spin_lock_irqsave(&pcpu_lock, flags); + pcpu_chunk_relocate(chunk, -1); + } else { + spin_lock_irqsave(&pcpu_lock, flags); } - spin_lock_irqsave(&pcpu_lock, flags); - pcpu_chunk_relocate(chunk, -1); + mutex_unlock(&pcpu_alloc_mutex); goto restart; area_found: spin_unlock_irqrestore(&pcpu_lock, flags); /* populate if not all pages are already there */ + mutex_lock(&pcpu_alloc_mutex); page_start = PFN_DOWN(off); page_end = PFN_UP(off + size); pcpu_for_each_unpop_region(chunk, rs, re, page_start, page_end) { WARN_ON(chunk->immutable); - if (pcpu_populate_chunk(chunk, rs, re)) { - spin_lock_irqsave(&pcpu_lock, flags); + ret = pcpu_populate_chunk(chunk, rs, re); + + spin_lock_irqsave(&pcpu_lock, flags); + if (ret) { + mutex_unlock(&pcpu_alloc_mutex); pcpu_free_area(chunk, off); err = "failed to populate"; goto fail_unlock; } - bitmap_set(chunk->populated, rs, re - rs); + spin_unlock_irqrestore(&pcpu_lock, flags); } mutex_unlock(&pcpu_alloc_mutex); @@ -832,8 +828,7 @@ area_found: fail_unlock: spin_unlock_irqrestore(&pcpu_lock, flags); -fail_unlock_mutex: - mutex_unlock(&pcpu_alloc_mutex); +fail: if (warn_limit) { pr_warning("PERCPU: allocation failed, size=%zu align=%zu, " "%s\n", size, align, err); |