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Diffstat (limited to 'mm/percpu.c')
-rw-r--r--mm/percpu.c75
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);