mirror of
git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs.git
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Igor Paunovic
6eff1d69da
rocket_remove() decrements rdev->num_cores for each core it removes,
while find_core_for_dev() searches slots 0 to num_cores - 1. Unbinding
the cores in the order they were bound therefore loses the last one: by
the time it is removed the search range has already shrunk past its
slot, so find_core_for_dev() returns -1 and rocket_remove() gives up
without doing anything.
num_cores never reaches zero, rocket_device_fini() never runs, and the
file-scoped rdev keeps pointing at a device that is going away. Binding
the cores again starts from that stale count, because rocket_probe()
takes rdev->num_cores as the slot to fill. On an RK3588, which describes
three cores, the second round lands on slots 1, 2 and 3 while rdev->cores
was allocated with room for three:
rocket fdab0000.npu: Rockchip NPU core 1 version: 1179210309
rocket fdac0000.npu: Rockchip NPU core 2 version: 1179210309
rocket fdad0000.npu: Rockchip NPU core 3 version: 1179210309
The write to rdev->cores[3] is past the end of the array.
Nothing in tree reads the core array often enough to notice, so the
overrun is silent today. It turned up while testing a devfreq series on
top of this, where a worker walks every core a few times a second, and
UBSAN caught the first bool it read out of the overrun entry:
UBSAN: invalid-load in drivers/accel/rocket/rocket_devfreq.c:47:10
load of value 5 is not a valid value for type '_Bool'
Workqueue: devfreq_wq devfreq_monitor
Record how many slots were allocated and search all of them. Every core
is then found on removal, num_cores reaches zero, the device is torn down
and a later bind starts from a clean rdev.
This does not make unbinding a single core out of several work. probe
still takes num_cores as the slot to fill, so rebinding one core while
its siblings stay bound would write over a slot that is already in use,
and rocket_open() still reaches for cores[0] whether or not anything is
there. Both of those want more thought than a fix should carry.
Found by unbinding and rebinding all three cores on an Orange Pi 5 Plus.
With this applied, 25 unbind/rebind rounds and 5 module unload/reload
rounds run clean there: the cores land in slots 0, 1 and 2 every time,
whichever order they are bound in, and the shared supply goes back to a
single user after each round.
Fixes: ed98261b41 ("accel/rocket: Add a new driver for Rockchip's NPU")
Cc: [email protected]
Signed-off-by: Igor Paunovic <[email protected]>
Assisted-by: LLM sparse checkpatch
Tested-by: Jiaxing Hu <[email protected]> # RK3576, two cores
Tested-by: Sidong Yang <[email protected]> # RK3588, 3 cores
Signed-off-by: Heiko Stuebner <[email protected]>
Link: https://patch.msgid.link/[email protected]
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