Messages in this thread | | | Date | Wed, 31 Mar 2021 10:07:20 -0300 | From | Jason Gunthorpe <> | Subject | Re: [PATCH v3 2/4] cxl/mem: Fix synchronization mechanism for device removal vs ioctl operations |
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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
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