linux/drivers/uio
Lang Dai 8fd0e2a6df uio: free uio id after uio file node is freed
uio_register_device() do two things.
1) get an uio id from a global pool, e.g. the id is <A>
2) create file nodes like /sys/class/uio/uio<A>

uio_unregister_device() do two things.
1) free the uio id <A> and return it to the global pool
2) free the file node /sys/class/uio/uio<A>

There is a situation is that one worker is calling uio_unregister_device(),
and another worker is calling uio_register_device().
If the two workers are X and Y, they go as below sequence,
1) X free the uio id <AAA>
2) Y get an uio id <AAA>
3) Y create file node /sys/class/uio/uio<AAA>
4) X free the file note /sys/class/uio/uio<AAA>
Then it will failed at the 3rd step and cause the phenomenon we saw as it
is creating a duplicated file node.

Failure reports as follows:
sysfs: cannot create duplicate filename '/class/uio/uio10'
Call Trace:
   sysfs_do_create_link_sd.isra.2+0x9e/0xb0
   sysfs_create_link+0x25/0x40
   device_add+0x2c4/0x640
   __uio_register_device+0x1c5/0x576 [uio]
   adf_uio_init_bundle_dev+0x231/0x280 [intel_qat]
   adf_uio_register+0x1c0/0x340 [intel_qat]
   adf_dev_start+0x202/0x370 [intel_qat]
   adf_dev_start_async+0x40/0xa0 [intel_qat]
   process_one_work+0x14d/0x410
   worker_thread+0x4b/0x460
   kthread+0x105/0x140
 ? process_one_work+0x410/0x410
 ? kthread_bind+0x40/0x40
 ret_from_fork+0x1f/0x40
 Code: 85 c0 48 89 c3 74 12 b9 00 10 00 00 48 89 c2 31 f6 4c 89 ef
 e8 ec c4 ff ff 4c 89 e2 48 89 de 48 c7 c7 e8 b4 ee b4 e8 6a d4 d7
 ff <0f> 0b 48 89 df e8 20 fa f3 ff 5b 41 5c 41 5d 5d c3 66 0f 1f 84
---[ end trace a7531c1ed5269e84 ]---
 c6xxvf b002:00:00.0: Failed to register UIO devices
 c6xxvf b002:00:00.0: Failed to register UIO devices

Signed-off-by: Lang Dai <lang.dai@intel.com>

Link: https://lore.kernel.org/r/1600054002-17722-1-git-send-email-lang.dai@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-09-17 18:52:03 +02:00
..
Kconfig treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
Makefile License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
uio.c uio: free uio id after uio file node is freed 2020-09-17 18:52:03 +02:00
uio_aec.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 333 2019-06-05 17:37:06 +02:00
uio_cif.c uio: add SPDX license tags 2018-07-21 15:41:20 +02:00
uio_dmem_genirq.c uio: disable lazy irq disable to avoid double fire 2020-07-03 11:02:21 +02:00
uio_fsl_elbc_gpcm.c uio: uio_fsl_elbc_gpcm: convert platform driver to use dev_groups 2019-08-02 12:56:51 +02:00
uio_hv_generic.c uio_hv_generic: add missed sysfs_remove_bin_file 2020-05-15 16:13:19 +02:00
uio_mf624.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 61 2019-05-24 17:36:45 +02:00
uio_netx.c uio: add SPDX license tags 2018-07-21 15:41:20 +02:00
uio_pci_generic.c uio/uio_pci_generic: Disable bus-mastering on release 2019-01-31 16:22:51 +01:00
uio_pdrv_genirq.c Merge branch 'char-misc-linus' into 'char-misc-next' 2020-07-10 13:42:33 +02:00
uio_pruss.c uio: pruss: fix error handling in probe 2018-08-02 10:14:26 +02:00
uio_sercos3.c uio: add SPDX license tags 2018-07-21 15:41:20 +02:00