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
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