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Yuwen Chen
2df7c4bd7c
When the user mounts the erofs second times, the decompression thread
may hung. The problem happens due to a sequence of steps like the
following:
1) Task A called z_erofs_load_lzma_config which obtain all of the node
from the z_erofs_lzma_head.
2) At this time, task B called the z_erofs_lzma_decompress and wanted to
get a node. But the z_erofs_lzma_head was empty, the Task B had to
sleep.
3) Task A release nodes and push nodes into the z_erofs_lzma_head. But
task B was still sleeping.
One example report when the hung happens:
task:kworker/u3:1 state:D stack:14384 pid: 86 ppid: 2 flags:0x00004000
Workqueue: erofs_unzipd z_erofs_decompressqueue_work
Call Trace:
<TASK>
__schedule+0x281/0x760
schedule+0x49/0xb0
z_erofs_lzma_decompress+0x4bc/0x580
? cpu_core_flags+0x10/0x10
z_erofs_decompress_pcluster+0x49b/0xba0
? __update_load_avg_se+0x2b0/0x330
? __update_load_avg_se+0x2b0/0x330
? update_load_avg+0x5f/0x690
? update_load_avg+0x5f/0x690
? set_next_entity+0xbd/0x110
? _raw_spin_unlock+0xd/0x20
z_erofs_decompress_queue.isra.0+0x2e/0x50
z_erofs_decompressqueue_work+0x30/0x60
process_one_work+0x1d3/0x3a0
worker_thread+0x45/0x3a0
? process_one_work+0x3a0/0x3a0
kthread+0xe2/0x110
? kthread_complete_and_exit+0x20/0x20
ret_from_fork+0x22/0x30
</TASK>
Signed-off-by: Yuwen Chen <chenyuwen1@meizu.com>
Fixes: 622ceaddb7 ("erofs: lzma compression support")
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20220626224041.4288-1-chenyuwen1@meizu.com
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
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 Restructured Text 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.