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Traffic monitor thread may see dangling stdout as the main thread closes and reassigns stdout without protection. This happens when the main thread finishes one subtest and moves to another one in the same netns_new() scope. The issue can be reproduced by running test_progs repeatedly with traffic monitor enabled: for ((i=1;i<=100;i++)); do ./test_progs -a flow_dissector_skb* -m '*' done For restoring stdout in crash_handler(), since it does not really care about closing stdout, simlpy flush stdout and restore it to the original one. Then, Fix the issue by consolidating stdio_restore_cleanup() and stdio_restore(), and protecting the use/close/assignment of stdout with a lock. The locking in the main thread is always performed regradless of whether traffic monitor is running or not for simplicity. It won't have any side-effect. Signed-off-by: Amery Hung <ameryhung@gmail.com> Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org> Acked-by: Eduard Zingerman <eddyz87@gmail.com> Link: https://patch.msgid.link/20250305182057.2802606-3-ameryhung@gmail.com 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 reStructuredText 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.