From: Bart Van Assche <bvanassche@acm.org>
To: Ming Lei <ming.lei@redhat.com>
Cc: "Martin K . Petersen" <martin.petersen@oracle.com>,
linux-scsi@vger.kernel.org, Luis Chamberlain <mcgrof@kernel.org>,
Christoph Hellwig <hch@lst.de>, Hannes Reinecke <hare@suse.de>,
John Garry <john.garry@huawei.com>,
Mike Christie <michael.christie@oracle.com>,
Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-modules@vger.kernel.org, linux-kernel@vger.kernel.org,
"James E.J. Bottomley" <jejb@linux.ibm.com>,
Tejun Heo <tj@kernel.org>
Subject: Re: [PATCH v5 6/7] module: Improve support for asynchronous module exit code
Date: Wed, 28 Sep 2022 12:27:07 -0700 [thread overview]
Message-ID: <2acc2220-65dc-4af5-ffd3-997f779d41c0@acm.org> (raw)
In-Reply-To: <YzOe3pYmn5qO9lFb@T590>
On 9/27/22 18:09, Ming Lei wrote:
> On Wed, Sep 14, 2022 at 03:56:20PM -0700, Bart Van Assche wrote:
>> Some kernel modules call device_del() from their module exit code and
>> schedule asynchronous work from inside the .release callback without waiting
>> until that callback has finished. As an example, many SCSI LLD drivers call
>
> It isn't only related with device, any kobject has such issue, or any
> reference counter usage has similar potential risk, see previous discussion:
>
> https://lore.kernel.org/lkml/YsZm7lSXYAHT14ui@T590/
>
> IMO, it is one fundamental problem wrt. module vs. reference counting or
> kobject uses at least, since the callback depends on module code
> segment.
>
>> scsi_remove_host() from their module exit code. scsi_remove_host() may
>> invoke scsi_device_dev_release_usercontext() asynchronously.
>> scsi_device_dev_release_usercontext() uses the host template pointer and
>> that pointer usually exists in static storage in the SCSI LLD. Support
>> using the module reference count to keep the module around until
>> asynchronous module exiting has completed by waiting in the delete_module()
>> system call until the module reference count drops to zero.
>
> The issue can't be addressed by the normal mod->refcnt, since user need
> to unload module when the device isn't used.
Hi Ming,
How about removing support for calling scsi_device_put() from atomic context
as is done in the untested patch below?
Thanks,
Bart.
diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index c59eac7a32f2..661753a10b47 100644
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -561,6 +561,8 @@ EXPORT_SYMBOL(scsi_report_opcode);
*/
int scsi_device_get(struct scsi_device *sdev)
{
+ might_sleep();
+
if (sdev->sdev_state == SDEV_DEL || sdev->sdev_state == SDEV_CANCEL)
goto fail;
if (!get_device(&sdev->sdev_gendev))
@@ -588,6 +590,7 @@ void scsi_device_put(struct scsi_device *sdev)
{
struct module *mod = sdev->host->hostt->module;
+ might_sleep();
put_device(&sdev->sdev_gendev);
module_put(mod);
}
diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index a3aaafdeac1d..4cfc9317b4ad 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -441,7 +441,7 @@ static void scsi_device_cls_release(struct device *class_dev)
put_device(&sdev->sdev_gendev);
}
-static void scsi_device_dev_release_usercontext(struct work_struct *work)
+static void scsi_device_dev_release(struct device *dev)
{
struct scsi_device *sdev;
struct device *parent;
@@ -450,11 +450,8 @@ static void scsi_device_dev_release_usercontext(struct work_struct *work)
struct scsi_vpd *vpd_pg0 = NULL, *vpd_pg89 = NULL;
struct scsi_vpd *vpd_pgb0 = NULL, *vpd_pgb1 = NULL, *vpd_pgb2 = NULL;
unsigned long flags;
- struct module *mod;
-
- sdev = container_of(work, struct scsi_device, ew.work);
- mod = sdev->host->hostt->module;
+ sdev = to_scsi_device(dev);
parent = sdev->sdev_gendev.parent;
@@ -516,19 +513,6 @@ static void scsi_device_dev_release_usercontext(struct work_struct *work)
if (parent)
put_device(parent);
- module_put(mod);
-}
-
-static void scsi_device_dev_release(struct device *dev)
-{
- struct scsi_device *sdp = to_scsi_device(dev);
-
- /* Set module pointer as NULL in case of module unloading */
- if (!try_module_get(sdp->host->hostt->module))
- sdp->host->hostt->module = NULL;
-
- execute_in_process_context(scsi_device_dev_release_usercontext,
- &sdp->ew);
}
static struct class sdev_class = {
next prev parent reply other threads:[~2022-09-28 19:27 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20220914225621.415631-1-bvanassche@acm.org>
2022-09-14 22:56 ` [PATCH v5 6/7] module: Improve support for asynchronous module exit code Bart Van Assche
2022-09-20 17:13 ` Bart Van Assche
2022-09-28 0:02 ` Luis Chamberlain
2022-09-28 18:17 ` Bart Van Assche
2022-09-30 19:39 ` Luis Chamberlain
2022-10-03 23:56 ` Luis Chamberlain
2022-10-04 0:24 ` Bart Van Assche
2022-09-28 1:09 ` Ming Lei
2022-09-28 19:27 ` Bart Van Assche [this message]
2022-09-29 1:10 ` Ming Lei
2022-09-29 17:27 ` Bart Van Assche
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=2acc2220-65dc-4af5-ffd3-997f779d41c0@acm.org \
--to=bvanassche@acm.org \
--cc=gregkh@linuxfoundation.org \
--cc=hare@suse.de \
--cc=hch@lst.de \
--cc=jejb@linux.ibm.com \
--cc=john.garry@huawei.com \
--cc=krzysztof.kozlowski@linaro.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-modules@vger.kernel.org \
--cc=linux-scsi@vger.kernel.org \
--cc=martin.petersen@oracle.com \
--cc=mcgrof@kernel.org \
--cc=michael.christie@oracle.com \
--cc=ming.lei@redhat.com \
--cc=tj@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).