libbpf-tools/offcputime: fix PID filters in PID namespaces - #5524
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usamoi
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June 18, 2026 13:39
In PID namespaces, the TGIDs and PIDs seen by users differ from the IDs seen by the kernel, causing the filters to fail. Fix this by using PID namespace TGIDs and PIDs for filtering and output.
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| struct bpf_pidns_info ns = {}; | ||
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| if (use_pidns && BPF_CORE_READ(t, pid) != 0) { | ||
| if (!bpf_get_ns_current_pid_tgid(pidns_dev, pidns_ino, &ns, sizeof(ns))) { |
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Don't kernel thread fail the bpf_get_ns_current_pid_tgid namespace translation?
If so, wouldn't allow_record return false early and completely filter out all kernel threads?
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Description
In PID namespaces, the TGIDs and PIDs seen by users differ from the IDs seen by the kernel, causing the filters to fail. Fix this by using PID namespace TGIDs and PIDs for filtering and output.
Why this approach
PID namespace TGIDs and PIDs must be stored as value instead of key, because there isn't a helper function that returns PID namespace TGIDs and PIDs of
task_struct *nextinsched_switch.Checklist
tools/toolname:,libbpf-tools/toolname:,src/cc:,docs:,build:,tests/python:)