760ebc4574
If 'struct rq' isn't defined in lock_contention.bpf.c then the type for
the 'runqueue' variable ends up being a forward declaration
(BTF_KIND_FWD) while the kernel has it defined (BTF_KIND_STRUCT).
This makes libbpf decide it has incompatible types and then fails to
load the BPF skeleton:
# perf lock con -ab sleep 1
libbpf: extern (var ksym) 'runqueues': incompatible types, expected [95] fwd rq, but kernel has [55509] struct rq
libbpf: failed to load object 'lock_contention_bpf'
libbpf: failed to load BPF skeleton 'lock_contention_bpf': -22
Failed to load lock-contention BPF skeleton
lock contention BPF setup failed
#
Add it as an empty struct to satisfy that type verification:
# perf lock con -ab sleep 1
contended total wait max wait avg wait type caller
2 50.64 us 25.38 us 25.32 us spinlock tick_do_update_jiffies64+0x25
1 26.18 us 26.18 us 26.18 us spinlock tick_do_update_jiffies64+0x25
#
Committer notes:
Extracted from a larger patch as Namhyung had already fixed the other
issues in
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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 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.