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56199bb956
There is a possibility to deadlock with an recursive
lock of the AP bus scan mutex ap_scan_bus_mutex:
... kernel: ============================================
... kernel: WARNING: possible recursive locking detected
... kernel: 5.14.0-496.el9.s390x #3 Not tainted
... kernel: --------------------------------------------
... kernel: kworker/12:1/130 is trying to acquire lock:
... kernel: 0000000358bc1510 (ap_scan_bus_mutex){+.+.}-{3:3}, at: ap_bus_force_rescan+0x92/0x108
... kernel:
but task is already holding lock:
... kernel: 0000000358bc1510 (ap_scan_bus_mutex){+.+.}-{3:3}, at: ap_scan_bus_wq_callback+0x28/0x60
... kernel:
other info that might help us debug this:
... kernel: Possible unsafe locking scenario:
... kernel: CPU0
... kernel: ----
... kernel: lock(ap_scan_bus_mutex);
... kernel: lock(ap_scan_bus_mutex);
... kernel:
*** DEADLOCK ***
Here is how the callstack looks like:
... [<00000003576fe9ce>] process_one_work+0x2a6/0x748
... [<0000000358150c00>] ap_scan_bus_wq_callback+0x40/0x60 <- mutex locked
... [<00000003581506e2>] ap_scan_bus+0x5a/0x3b0
... [<000000035815037c>] ap_scan_adapter+0x5b4/0x8c0
... [<000000035814fa34>] ap_scan_domains+0x2d4/0x668
... [<0000000357d989b4>] device_add+0x4a4/0x6b8
... [<0000000357d9bb54>] bus_probe_device+0xb4/0xc8
... [<0000000357d9daa8>] __device_attach+0x120/0x1b0
... [<0000000357d9a632>] bus_for_each_drv+0x8a/0xd0
... [<0000000357d9d548>] __device_attach_driver+0xc0/0x140
... [<0000000357d9d3d8>] driver_probe_device+0x40/0xf0
... [<0000000357d9cec2>] really_probe+0xd2/0x460
... [<000000035814d7b0>] ap_device_probe+0x150/0x208
... [<000003ff802a5c46>] zcrypt_cex4_queue_probe+0xb6/0x1c0 [zcrypt_cex4]
... [<000003ff7fb2d36e>] zcrypt_queue_register+0xe6/0x1b0 [zcrypt]
... [<000003ff7fb2c8ac>] zcrypt_rng_device_add+0x94/0xd8 [zcrypt]
... [<0000000357d7bc52>] hwrng_register+0x212/0x228
... [<0000000357d7b8c2>] add_early_randomness+0x102/0x110
... [<000003ff7fb29c94>] zcrypt_rng_data_read+0x94/0xb8 [zcrypt]
... [<0000000358150aca>] ap_bus_force_rescan+0x92/0x108
... [<0000000358177572>] mutex_lock_interruptible_nested+0x32/0x40 <- lock again
Note this only happens when the very first random data providing
crypto card appears via hot plug in the system AND is in disabled
state ("deconfig"). Then the initial pull of random data fails and
a re-scan of the AP bus is triggered while already in the middle
of an AP bus scan caused by the appearing new hardware.
The fix is relatively simple once the scenario us understood:
The AP bus force rescan function will immediately return if there
is currently an AP bus scan running with the very same thread id.
Fixes:
|
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.