From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:47263 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755058AbcGYVbx (ORCPT ); Mon, 25 Jul 2016 17:31:53 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Tejun Heo , Vlastimil Babka , Sasha Levin Subject: [PATCH 4.6 103/203] percpu: fix synchronization between synchronous map extension and chunk destruction Date: Mon, 25 Jul 2016 13:55:18 -0700 Message-Id: <20160725203433.558514378@linuxfoundation.org> In-Reply-To: <20160725203429.221747288@linuxfoundation.org> References: <20160725203429.221747288@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Tejun Heo commit 6710e594f71ccaad8101bc64321152af7cd9ea28 upstream. 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 Fixes: 1a4d76076cda ("percpu: implement asynchronous chunk population") Signed-off-by: Greg Kroah-Hartman --- mm/percpu.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) --- a/mm/percpu.c +++ b/mm/percpu.c @@ -162,7 +162,7 @@ static struct pcpu_chunk *pcpu_reserved_ 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 p 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 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; }