[FS#804] mt7621: kernel errors - rcu_sched detected stalls on CPUs/tasks

[LEDE Bugs]

The following task has a new comment added:

FS#804 - mt7621: kernel errors - rcu_sched detected stalls on CPUs/tasks
User who did this - Zhong Jianxin (azuwis)

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    @Zhong Jianxin: will it work even with a modified kernel (since we change patches used in upstream)?

It depends on the modification, in this case, it should work.

The reason why there are so many `unknown symbol` is that some kernel configs are only enabled when certain packages selected, e.g. select kmod-fs-f2fs will enable [[https://git.lede-project.org/?p=source.git;a=blob;f=package/kernel/linux/modules/fs.mk;h=610d1b58a1ae453409eea2704c5037074f86c4ae;hb=HEAD#l207|this kernel configs]]:

    CONFIG_F2FS_FS
    CONFIG_F2FS_STAT_FS=y
    CONFIG_F2FS_FS_XATTR=y
    CONFIG_F2FS_FS_POSIX_ACL=n
    CONFIG_F2FS_FS_SECURITY=n
    CONFIG_F2FS_CHECK_FS=n

Upstream snapshot build will select many packages, but it's probably not the case of custom build.

Here is another way to build as close as upstream snapshot:

    $ wget https://downloads.lede-project.org/snapshots/targets/ramips/mt7621/config.seed -O .config
    $ make defconfig
    $ make clean
    $ make

But it will take much longer time.

Just tested this, it built the some kernel version as current upstream snapshot, without override LINUX_VERMAGIC.
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More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=804#comment3104