This is a note to let you know that I've just added the patch titled device-dax: fix percpu_ref_exit ordering to the 4.8-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: device-dax-fix-percpu_ref_exit-ordering.patch and it can be found in the queue-4.8 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 52e73eb2872c9af6f382b2b22954ca8214397a4e Mon Sep 17 00:00:00 2001 From: Dan Williams <dan.j.williams@xxxxxxxxx> Date: Thu, 27 Oct 2016 17:04:05 -0700 Subject: device-dax: fix percpu_ref_exit ordering From: Dan Williams <dan.j.williams@xxxxxxxxx> commit 52e73eb2872c9af6f382b2b22954ca8214397a4e upstream. We need to wait until the percpu_ref is released before exit. Otherwise, we sometimes lose the race and trigger this new warning that was added in v4.9 (commit a67823c1ed10 "percpu-refcount: init ->confirm_switch member properly"): WARNING: CPU: 0 PID: 3629 at lib/percpu-refcount.c:107 percpu_ref_exit+0x51/0x60 [..] Call Trace: [<ffffffff814bf093>] dump_stack+0x85/0xc2 [<ffffffff810b15db>] __warn+0xcb/0xf0 [<ffffffff810b170d>] warn_slowpath_null+0x1d/0x20 [<ffffffff814d70c1>] percpu_ref_exit+0x51/0x60 [<ffffffffa005706a>] dax_pmem_percpu_exit+0x1a/0x50 [dax_pmem] [<ffffffff81615f1f>] devm_action_release+0xf/0x20 Fixes: ab68f2622136 ("/dev/dax, pmem: direct access to persistent memory") Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/dax/pmem.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/dax/pmem.c +++ b/drivers/dax/pmem.c @@ -44,7 +44,6 @@ static void dax_pmem_percpu_exit(void *d dev_dbg(dax_pmem->dev, "%s\n", __func__); percpu_ref_exit(ref); - wait_for_completion(&dax_pmem->cmp); } static void dax_pmem_percpu_kill(void *data) @@ -54,6 +53,7 @@ static void dax_pmem_percpu_kill(void *d dev_dbg(dax_pmem->dev, "%s\n", __func__); percpu_ref_kill(ref); + wait_for_completion(&dax_pmem->cmp); } static int dax_pmem_probe(struct device *dev) Patches currently in stable-queue which might be from dan.j.williams@xxxxxxxxx are queue-4.8/device-dax-fix-percpu_ref_exit-ordering.patch -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html