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 v3 2/4] cxl/mem: Fix synchronization mechanism for device removal vs ioctl operations
Date: Wed, 31 Mar 2021 10:07:20 -0300 [thread overview]
Message-ID: <20210331130720.GF1463678@nvidia.com> (raw)
In-Reply-To: <161714739718.2168142.17960000558666300914.stgit@dwillia2-desk3.amr.corp.intel.com>
On Tue, Mar 30, 2021 at 04:36:37PM -0700, Dan Williams wrote:
> -static void cxlmdev_unregister(void *_cxlmd)
> +static void cxl_memdev_activate(struct cxl_memdev *cxlmd, struct cxl_mem *cxlm)
> {
> - struct cxl_memdev *cxlmd = _cxlmd;
> - struct device *dev = &cxlmd->dev;
> + cxlmd->cxlm = cxlm;
> + down_write(&cxl_memdev_rwsem);
> + up_write(&cxl_memdev_rwsem);
> +}
No reason not to put the assignment inside the lock. Though using the
lock at all is overkill as the pointer hasn't left the local stack
frame at this point.
> err_add:
> - ida_free(&cxl_memdev_ida, cxlmd->id);
> -err_id:
> /*
> - * Theoretically userspace could have already entered the fops,
> - * so flush ops_active.
> + * The cdev was briefly live, shutdown any ioctl operations that
> + * saw that state.
> */
Wow it is really subtle that cdev_device_add has this tiny hole where
it can fail but have already allowed open() :<
Other than the lock it looks OK
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Jason
next prev parent reply other threads:[~2021-03-31 13:08 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-30 23:36 [PATCH v3 0/4] cxl/mem: Fix memdev device setup Dan Williams
2021-03-30 23:36 ` [PATCH v3 1/4] cxl/mem: Use sysfs_emit() for attribute show routines Dan Williams
2021-03-30 23:36 ` [PATCH v3 2/4] cxl/mem: Fix synchronization mechanism for device removal vs ioctl operations Dan Williams
2021-03-31 13:07 ` Jason Gunthorpe [this message]
2021-03-31 15:45 ` Dan Williams
2021-03-30 23:36 ` [PATCH v3 3/4] cxl/mem: Do not rely on device_add() side effects for dev_set_name() failures Dan Williams
2021-03-31 13:09 ` Jason Gunthorpe
2021-03-31 16:04 ` Dan Williams
2021-03-31 16:17 ` Jason Gunthorpe
2021-03-31 16:32 ` Dan Williams
2021-03-30 23:36 ` [PATCH v3 4/4] cxl/mem: Disable cxl device power management Dan Williams
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