Messages in this thread | ![/](/images/icornerl.gif) | | Subject | [PATCH 0/3] cdev: Generic shutdown handling | From | Dan Williams <> | Date | Wed, 20 Jan 2021 11:38:52 -0800 |
| |
After reviewing driver submissions with new cdev + ioctl usages one common stumbling block is coordinating the shutdown of the ioctl path, or other file operations, at driver ->remove() time. While cdev_del() guarantees that no new file descriptors will be established, operations on existing file descriptors can proceed indefinitely.
Given the observation that the kernel spends the resources for a percpu_ref per request_queue shared with all block_devices on a gendisk, do the same for all the cdev instances that share the same cdev_add()-to-cdev_del() lifetime.
With this in place cdev_del() not only guarantees 'no new opens', but it also guarantees 'no new operations invocations' and 'all threads running in an operation handler have exited that handler'.
As a proof point of the way driver implementations open-code around this gap in the api the libnvdimm ioctl path is reworked with a result of:
4 files changed, 101 insertions(+), 153 deletions(-)
---
Dan Williams (3): cdev: Finish the cdev api with queued mode support libnvdimm/ida: Switch to non-deprecated ida helpers libnvdimm/ioctl: Switch to cdev_register_queued()
drivers/nvdimm/btt_devs.c | 6 + drivers/nvdimm/bus.c | 177 +++++++++------------------------------ drivers/nvdimm/core.c | 14 ++- drivers/nvdimm/dax_devs.c | 4 - drivers/nvdimm/dimm_devs.c | 53 +++++++++--- drivers/nvdimm/namespace_devs.c | 14 +-- drivers/nvdimm/nd-core.h | 14 ++- drivers/nvdimm/pfn_devs.c | 4 - fs/char_dev.c | 108 ++++++++++++++++++++++-- include/linux/cdev.h | 21 ++++- 10 files changed, 238 insertions(+), 177 deletions(-)
| ![\](/images/icornerr.gif) |