From: Dan Williams <dan.j.williams@intel.com>
To: alexander.h.duyck@linux.intel.com
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Greg KH <gregkh@linuxfoundation.org>,
linux-nvdimm <linux-nvdimm@lists.01.org>,
Tejun Heo <tj@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Linux-pm mailing list <linux-pm@vger.kernel.org>,
jiangshanlai@gmail.com, "Rafael J. Wysocki" <rafael@kernel.org>,
"Brown, Len" <len.brown@intel.com>, Pavel Machek <pavel@ucw.cz>,
zwisler@kernel.org, Dave Jiang <dave.jiang@intel.com>,
bvanassche@acm.org
Subject: Re: [driver-core PATCH v5 5/9] driver core: Establish clear order of operations for deferred probe and remove
Date: Mon, 26 Nov 2018 18:35:05 -0800 [thread overview]
Message-ID: <CAPcyv4ieNzbx5iN74ZCAKDesgYt_67iM_DC-A35M=Z9jfR+YAQ@mail.gmail.com> (raw)
In-Reply-To: <154145232484.29224.1635232599636954462.stgit@ahduyck-desk1.jf.intel.com>
On Mon, Nov 5, 2018 at 1:12 PM Alexander Duyck
<alexander.h.duyck@linux.intel.com> wrote:
>
> This patch adds an additional bit to the device struct named async_probe.
> This additional bit allows us to guarantee ordering between probe and
> remove operations.
>
> This allows us to guarantee that if we execute a remove operation or a
> driver load attempt on a given interface it will not attempt to update the
> driver member asynchronously following the earlier operation. Previously
> this guarantee was not present and could result in us attempting to remove
> a driver from an interface only to have it show up later when it is
> asynchronously loaded.
>
> One change I made in addition is I replaced the use of "bool X:1" to define
> the bitfield to a "u8 X:1" setup in order to resolve some checkpatch
> warnings.
The usage of "us" in the changelog through me off, please reword this
to explicitly state the subject like: "The additional bit allows the
driver core to guarantee ordering between probe and remove
operations."
> Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
> ---
> drivers/base/dd.c | 104 +++++++++++++++++++++++++++---------------------
> include/linux/device.h | 9 ++--
> 2 files changed, 64 insertions(+), 49 deletions(-)
>
> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> index e74cefeb5b69..ed19cf0d6f9a 100644
> --- a/drivers/base/dd.c
> +++ b/drivers/base/dd.c
> @@ -472,6 +472,8 @@ static int really_probe(struct device *dev, struct device_driver *drv)
> drv->bus->name, __func__, drv->name, dev_name(dev));
> WARN_ON(!list_empty(&dev->devres_head));
>
> + /* clear async_probe flag as we are no longer deferring driver load */
> + dev->async_probe = false;
> re_probe:
> dev->driver = drv;
>
> @@ -771,6 +773,10 @@ static void __device_attach_async_helper(void *_dev, async_cookie_t cookie)
>
> device_lock(dev);
>
> + /* nothing to do if async_probe has been cleared */
> + if (!dev->async_probe)
> + goto out_unlock;
> +
> if (dev->parent)
> pm_runtime_get_sync(dev->parent);
>
> @@ -781,7 +787,7 @@ static void __device_attach_async_helper(void *_dev, async_cookie_t cookie)
>
> if (dev->parent)
> pm_runtime_put(dev->parent);
> -
> +out_unlock:
> device_unlock(dev);
>
> put_device(dev);
> @@ -826,6 +832,7 @@ static int __device_attach(struct device *dev, bool allow_async)
> */
> dev_dbg(dev, "scheduling asynchronous probe\n");
> get_device(dev);
> + dev->async_probe = true;
> async_schedule(__device_attach_async_helper, dev);
> } else {
> pm_request_idle(dev);
> @@ -971,62 +978,69 @@ EXPORT_SYMBOL_GPL(driver_attach);
> */
> static void __device_release_driver(struct device *dev, struct device *parent)
> {
> - struct device_driver *drv;
> + struct device_driver *drv = dev->driver;
>
> - drv = dev->driver;
> - if (drv) {
> - while (device_links_busy(dev)) {
> - __device_driver_unlock(dev, parent);
> + /*
> + * In the event that we are asked to release the driver on an
> + * interface that is still waiting on a probe we can just terminate
> + * the probe by setting async_probe to false. When the async call
> + * is finally completed it will see this state and just exit.
> + */
> + dev->async_probe = false;
> + if (!drv)
> + return;
Patch 4 deleted the async_synchronize_full() that would have flushed
in-flight ->probe() relative to the current ->remove(). If remove runs
before probe then would seem to be deadlock condition, but if
->remove() runs before probe then dev->driver is NULL and we abort. So
I'm struggling to see what value dev->async_probe provides over
dev->driver?
next prev parent reply other threads:[~2018-11-27 2:35 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-05 21:11 [driver-core PATCH v5 0/9] Add NUMA aware async_schedule calls Alexander Duyck
2018-11-05 21:11 ` [driver-core PATCH v5 1/9] workqueue: Provide queue_work_node to queue work near a given NUMA node Alexander Duyck
2018-11-06 0:42 ` Bart Van Assche
2018-11-06 16:27 ` Alexander Duyck
2018-11-05 21:11 ` [driver-core PATCH v5 2/9] async: Add support for queueing on specific " Alexander Duyck
2018-11-07 0:50 ` Bart Van Assche
2018-11-05 21:11 ` [driver-core PATCH v5 3/9] device core: Consolidate locking and unlocking of parent and device Alexander Duyck
2018-11-05 21:11 ` [driver-core PATCH v5 4/9] driver core: Move async_synchronize_full call Alexander Duyck
2018-11-06 1:04 ` Bart Van Assche
2018-11-06 16:18 ` Alexander Duyck
2018-11-06 17:22 ` Bart Van Assche
2018-11-05 21:12 ` [driver-core PATCH v5 5/9] driver core: Establish clear order of operations for deferred probe and remove Alexander Duyck
2018-11-06 4:10 ` kbuild test robot
2018-11-06 23:51 ` Bart Van Assche
2018-11-07 0:52 ` Alexander Duyck
2018-11-23 1:23 ` Rong Chen
2018-11-23 14:19 ` Bart Van Assche
2018-11-06 23:48 ` Bart Van Assche
2018-11-07 1:34 ` Joe Perches
2018-11-08 23:42 ` Bart Van Assche
2018-11-11 14:31 ` Pavel Machek
2018-11-27 2:35 ` Dan Williams [this message]
2018-11-27 16:49 ` Alexander Duyck
2018-11-05 21:12 ` [driver-core PATCH v5 6/9] driver core: Probe devices asynchronously instead of the driver Alexander Duyck
2018-11-07 0:22 ` Bart Van Assche
2018-11-05 21:12 ` [driver-core PATCH v5 7/9] driver core: Attach devices on CPU local to device node Alexander Duyck
2018-11-07 0:24 ` Bart Van Assche
2018-11-05 21:12 ` [driver-core PATCH v5 8/9] PM core: Use new async_schedule_dev command Alexander Duyck
2018-11-07 0:24 ` Bart Van Assche
2018-11-05 21:12 ` [driver-core PATCH v5 9/9] libnvdimm: Schedule device registration on node local to the device Alexander Duyck
2018-11-07 0:26 ` Bart Van Assche
2018-11-06 0:50 ` [driver-core PATCH v5 0/9] Add NUMA aware async_schedule calls Bart Van Assche
2018-11-06 16:25 ` Alexander Duyck
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CAPcyv4ieNzbx5iN74ZCAKDesgYt_67iM_DC-A35M=Z9jfR+YAQ@mail.gmail.com' \
--to=dan.j.williams@intel.com \
--cc=akpm@linux-foundation.org \
--cc=alexander.h.duyck@linux.intel.com \
--cc=bvanassche@acm.org \
--cc=dave.jiang@intel.com \
--cc=gregkh@linuxfoundation.org \
--cc=jiangshanlai@gmail.com \
--cc=len.brown@intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-nvdimm@lists.01.org \
--cc=linux-pm@vger.kernel.org \
--cc=pavel@ucw.cz \
--cc=rafael@kernel.org \
--cc=tj@kernel.org \
--cc=zwisler@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).