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authorTejun Heo <tj@kernel.org>2016-05-25 11:48:25 -0400
committerTejun Heo <tj@kernel.org>2016-05-25 11:48:25 -0400
commit6710e594f71ccaad8101bc64321152af7cd9ea28 (patch)
tree526322970c44a03be3b46d27e45644fa188886fb
parent4f996e234dad488e5d9ba0858bc1bae12eff82c3 (diff)
percpu: fix synchronization between synchronous map extension and chunk destruction
For non-atomic allocations, pcpu_alloc() can try to extend the area map synchronously after dropping pcpu_lock; however, the extension wasn't synchronized against chunk destruction and the chunk might get freed while extension is in progress. This patch fixes the bug by putting most of non-atomic allocations under pcpu_alloc_mutex to synchronize against pcpu_balance_work which is responsible for async chunk management including destruction. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-and-tested-by: Alexei Starovoitov <alexei.starovoitov@gmail.com> Reported-by: Vlastimil Babka <vbabka@suse.cz> Reported-by: Sasha Levin <sasha.levin@oracle.com> Cc: stable@vger.kernel.org # v3.18+ Fixes: 1a4d76076cda ("percpu: implement asynchronous chunk population")
-rw-r--r--mm/percpu.c16
1 files changed, 8 insertions, 8 deletions
diff --git a/mm/percpu.c b/mm/percpu.c
index b1d2a38..9903830 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -162,7 +162,7 @@ static struct pcpu_chunk *pcpu_reserved_chunk;
static int pcpu_reserved_chunk_limit;
static DEFINE_SPINLOCK(pcpu_lock); /* all internal data structures */
-static DEFINE_MUTEX(pcpu_alloc_mutex); /* chunk create/destroy, [de]pop */
+static DEFINE_MUTEX(pcpu_alloc_mutex); /* chunk create/destroy, [de]pop, map ext */
static struct list_head *pcpu_slot __read_mostly; /* chunk list slots */
@@ -444,6 +444,8 @@ static int pcpu_extend_area_map(struct pcpu_chunk *chunk, int new_alloc)
size_t old_size = 0, new_size = new_alloc * sizeof(new[0]);
unsigned long flags;
+ lockdep_assert_held(&pcpu_alloc_mutex);
+
new = pcpu_mem_zalloc(new_size);
if (!new)
return -ENOMEM;
@@ -890,6 +892,9 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved,
return NULL;
}
+ if (!is_atomic)
+ mutex_lock(&pcpu_alloc_mutex);
+
spin_lock_irqsave(&pcpu_lock, flags);
/* serve reserved allocations from the reserved chunk if available */
@@ -962,12 +967,9 @@ restart:
if (is_atomic)
goto fail;
- mutex_lock(&pcpu_alloc_mutex);
-
if (list_empty(&pcpu_slot[pcpu_nr_slots - 1])) {
chunk = pcpu_create_chunk();
if (!chunk) {
- mutex_unlock(&pcpu_alloc_mutex);
err = "failed to allocate new chunk";
goto fail;
}
@@ -978,7 +980,6 @@ restart:
spin_lock_irqsave(&pcpu_lock, flags);
}
- mutex_unlock(&pcpu_alloc_mutex);
goto restart;
area_found:
@@ -988,8 +989,6 @@ area_found:
if (!is_atomic) {
int page_start, page_end, rs, re;
- mutex_lock(&pcpu_alloc_mutex);
-
page_start = PFN_DOWN(off);
page_end = PFN_UP(off + size);
@@ -1000,7 +999,6 @@ area_found:
spin_lock_irqsave(&pcpu_lock, flags);
if (ret) {
- mutex_unlock(&pcpu_alloc_mutex);
pcpu_free_area(chunk, off, &occ_pages);
err = "failed to populate";
goto fail_unlock;
@@ -1040,6 +1038,8 @@ fail:
/* see the flag handling in pcpu_blance_workfn() */
pcpu_atomic_alloc_failed = true;
pcpu_schedule_balance_work();
+ } else {
+ mutex_unlock(&pcpu_alloc_mutex);
}
return NULL;
}