From 664646c5863e13607733f29891d655a51f5ab3ff Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Wed, 25 May 2016 11:48:25 -0400 Subject: percpu: fix synchronization between synchronous map extension and chunk destruction [ Upstream commit 6710e594f71ccaad8101bc64321152af7cd9ea28 ] 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 Reported-and-tested-by: Alexei Starovoitov Reported-by: Vlastimil Babka Reported-by: Sasha Levin Cc: stable@vger.kernel.org # v3.18+ Fixes: 1a4d76076cda ("percpu: implement asynchronous chunk population") Signed-off-by: Sasha Levin --- mm/percpu.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) (limited to 'mm') diff --git a/mm/percpu.c b/mm/percpu.c index ca3264042451..5ae6e0284967 100644 --- a/mm/percpu.c +++ b/mm/percpu.c @@ -160,7 +160,7 @@ 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 */ @@ -446,6 +446,8 @@ 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; @@ -892,6 +894,9 @@ 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 */ @@ -964,12 +969,9 @@ 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; } @@ -980,7 +982,6 @@ restart: spin_lock_irqsave(&pcpu_lock, flags); } - mutex_unlock(&pcpu_alloc_mutex); goto restart; area_found: @@ -990,8 +991,6 @@ 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); @@ -1002,7 +1001,6 @@ 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; @@ -1042,6 +1040,8 @@ 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; } -- cgit v1.2.3