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Alexei Starovoitov
cb5dc5b062
Song Liu says: ==================== LOCKDEP NMI warning highlighted potential deadlock of hashtab in NMI context: [ 74.828971] ================================ [ 74.828972] WARNING: inconsistent lock state [ 74.828973] 5.9.0-rc8+ #275 Not tainted [ 74.828974] -------------------------------- [ 74.828975] inconsistent {INITIAL USE} -> {IN-NMI} usage. [ 74.828976] taskset/1174 [HC2[2]:SC0[0]:HE0:SE1] takes: [...] [ 74.828999] Possible unsafe locking scenario: [ 74.828999] [ 74.829000] CPU0 [ 74.829001] ---- [ 74.829001] lock(&htab->buckets[i].raw_lock); [ 74.829003] <Interrupt> [ 74.829004] lock(&htab->buckets[i].raw_lock); Please refer to patch 1/2 for full trace. This warning is a false alert, as "INITIAL USE" and "IN-NMI" in the tests are from different hashtab. On the other hand, in theory, it is possible to deadlock when a hashtab is access from both non-NMI and NMI context. Patch 1/2 fixes this false alert by assigning separate lockdep class to each hashtab. Patch 2/2 introduces map_locked counters, which is similar to bpf_prog_active counter, to avoid hashtab deadlock in NMI context. ==================== Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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.