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If a reboot/shutdown signal with double force (-ff) is triggered when
the erase worker or wear-leveling worker function runs we may end up in
a race condition since the MTD device gets a reboot notification and
suspends the nand flash before the erase or wear-leveling is done. This
will reject all accesses to the flash with -EBUSY.
Sequence for the erase worker function:
systemctl reboot -ff ubi_thread
do_work
__do_sys_reboot
blocking_notifier_call_chain
mtd_reboot_notifier
nand_shutdown
nand_suspend
__erase_worker
ubi_sync_erase
mtd_erase
nand_erase_nand
# Blocked by suspended chip
nand_get_device
=> EBUSY
Similar sequence for the wear-leveling function:
systemctl reboot -ff ubi_thread
do_work
__do_sys_reboot
blocking_notifier_call_chain
mtd_reboot_notifier
nand_shutdown
nand_suspend
wear_leveling_worker
ubi_eba_copy_leb
ubi_io_write
mtd_write
nand_write_oob
# Blocked by suspended chip
nand_get_device
=> EBUSY
systemd-shutdown[1]: Rebooting.
ubi0 error: ubi_io_write: error -16 while writing 2048 bytes to PEB
CPU: 1 PID: 82 Comm: ubi_bgt0d Kdump: loaded Tainted: G O
(unwind_backtrace) from [<80107b9f>] (show_stack+0xb/0xc)
(show_stack) from [<8033641f>] (dump_stack_lvl+0x2b/0x34)
(dump_stack_lvl) from [<803b7f3f>] (ubi_io_write+0x3ab/0x4a8)
(ubi_io_write) from [<803b817d>] (ubi_io_write_vid_hdr+0x71/0xb4)
(ubi_io_write_vid_hdr) from [<803b6971>] (ubi_eba_copy_leb+0x195/0x2f0)
(ubi_eba_copy_leb) from [<803b939b>] (wear_leveling_worker+0x2ff/0x738)
(wear_leveling_worker) from [<803b86ef>] (do_work+0x5b/0xb0)
(do_work) from [<803b9ee1>] (ubi_thread+0xb1/0x11c)
(ubi_thread) from [<8012c113>] (kthread+0x11b/0x134)
(kthread) from [<80100139>] (ret_from_fork+0x11/0x38)
Exception stack(0x80c43fb0 to 0x80c43ff8)
...
ubi0 error: ubi_dump_flash: err -16 while reading 2048 bytes from PEB
ubi0 error: wear_leveling_worker: error -16 while moving PEB 246 to PEB
ubi0 warning: ubi_ro_mode.part.0: switch to read-only mode
...
ubi0 error: do_work: work failed with error code -16
ubi0 error: ubi_thread: ubi_bgt0d: work failed with error code -16
...
Kernel panic - not syncing: Software Watchdog Timer expired
Add a reboot notification for the ubi/wear-leveling to shutdown any
potential flash work actions before the nand is suspended.
Signed-off-by: Mårten Lindahl <marten.lindahl@axis.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
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.