Re: [PATCH bpf-next v5 3/3] selftests/bpf: Fix dangling stdout seen by traffic monitor thread

[Eduard Zingerman <eddyz87@gmail.com>]

On Wed, 2025-03-05 at 10:20 -0800, Amery Hung wrote:
> 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>
> ---

Acked-by: Eduard Zingerman <eddyz87@gmail.com>

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