From: Jason Gunthorpe <jgg@nvidia.com>
To: Dan Williams <dan.j.williams@intel.com>
Cc: linux-cxl@vger.kernel.org, linux-kernel@vger.kernel.org,
vishal.l.verma@intel.com, ira.weiny@intel.com,
alison.schofield@intel.com
Subject: Re: [PATCH v2 2/4] cxl/mem: Fix synchronization mechanism for device removal vs ioctl operations
Date: Tue, 30 Mar 2021 08:16:20 -0300 [thread overview]
Message-ID: <20210330111620.GK2356281@nvidia.com> (raw)
In-Reply-To: <161707246948.2072157.2116502455691653472.stgit@dwillia2-desk3.amr.corp.intel.com>
On Mon, Mar 29, 2021 at 07:47:49PM -0700, Dan Williams wrote:
> @@ -1155,21 +1175,12 @@ static void cxlmdev_unregister(void *_cxlmd)
> struct cxl_memdev *cxlmd = _cxlmd;
> struct device *dev = &cxlmd->dev;
>
> - percpu_ref_kill(&cxlmd->ops_active);
> cdev_device_del(&cxlmd->cdev, dev);
> - wait_for_completion(&cxlmd->ops_dead);
> + synchronize_srcu(&cxl_memdev_srcu);
This needs some kind of rcu protected pointer for SRCU to to
work.. The write side has to null the pointer and the read side has to
copy the pointer to the stack and check for NULL.
Otherwise the read side can't detect when the write side is shutting
down.
Basically you must use rcu_derference(), rcu_assign_pointer(), etc
when working with RCU.
Something like 'ops' is usually a reasonable choice
This really can't just be a simple rwsem?
Jason
next prev parent reply other threads:[~2021-03-30 11:17 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-30 2:47 [PATCH v2 0/4] cxl/mem: Fix memdev device setup Dan Williams
2021-03-30 2:47 ` [PATCH v2 1/4] cxl/mem: Use sysfs_emit() for attribute show routines Dan Williams
2021-03-30 2:47 ` [PATCH v2 2/4] cxl/mem: Fix synchronization mechanism for device removal vs ioctl operations Dan Williams
2021-03-30 11:16 ` Jason Gunthorpe [this message]
2021-03-30 15:37 ` Dan Williams
2021-03-30 15:47 ` Jason Gunthorpe
2021-03-30 16:05 ` Dan Williams
2021-03-30 17:02 ` Jason Gunthorpe
2021-03-30 17:31 ` Dan Williams
2021-03-30 17:54 ` Jason Gunthorpe
2021-03-30 19:00 ` Dan Williams
2021-03-30 19:26 ` Jason Gunthorpe
2021-03-30 19:43 ` Dan Williams
2021-03-30 19:51 ` Jason Gunthorpe
2021-03-30 21:00 ` Dan Williams
2021-03-30 22:09 ` Jason Gunthorpe
2021-03-30 2:47 ` [PATCH v2 3/4] cxl/mem: Do not rely on device_add() side effects for dev_set_name() failures Dan Williams
2021-03-30 2:48 ` [PATCH v2 4/4] cxl/mem: Disable cxl device power management Dan Williams
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