Yafang Shao b6c7abd1c2 tracing: Fix TASK_COMM_LEN in trace event format file ... After commit 3087c61ed2 ("tools/testing/selftests/bpf: replace open-coded 16 with TASK_COMM_LEN"), the content of the format file under /sys/kernel/tracing/events/task/task_newtask was changed from field:char comm[16]; offset:12; size:16; signed:0; to field:char comm[TASK_COMM_LEN]; offset:12; size:16; signed:0; John reported that this change breaks older versions of perfetto. Then Mathieu pointed out that this behavioral change was caused by the use of __stringify(_len), which happens to work on macros, but not on enum labels. And he also gave the suggestion on how to fix it: :One possible solution to make this more robust would be to extend :struct trace_event_fields with one more field that indicates the length :of an array as an actual integer, without storing it in its stringified :form in the type, and do the formatting in f_show where it belongs. The result as follows after this change, $ cat /sys/kernel/tracing/events/task/task_newtask/format field:char comm[16]; offset:12; size:16; signed:0; Link: https://lore.kernel.org/lkml/Y+QaZtz55LIirsUO@google.com/ Link: https://lore.kernel.org/linux-trace-kernel/20230210155921.4610-1-laoar.shao@gmail.com/ Link: https://lore.kernel.org/linux-trace-kernel/20230212151303.12353-1-laoar.shao@gmail.com Cc: stable@vger.kernel.org Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com> Cc: Kajetan Puchalski <kajetan.puchalski@arm.com> CC: Qais Yousef <qyousef@layalina.io> Fixes: 3087c61ed2 ("tools/testing/selftests/bpf: replace open-coded 16 with TASK_COMM_LEN") Reported-by: John Stultz <jstultz@google.com> Debugged-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Suggested-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Suggested-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Yafang Shao <laoar.shao@gmail.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>		2023-02-12 10:23:39 -05:00
..
events	rxrpc: Move client call connection to the I/O thread	2023-01-06 09:43:33 +00:00
misc	NFSD: add CB_RECALL_ANY tracepoints	2022-12-10 11:01:12 -05:00
stages	tracing: Fix TASK_COMM_LEN in trace event format file	2023-02-12 10:23:39 -05:00
bpf_probe.h	tracing: Add __cpumask to denote a trace event field that is a cpumask_t	2022-11-23 19:08:30 -05:00
define_custom_trace.h	tracing: Add TRACE_CUSTOM_EVENT() macro	2022-03-11 11:49:24 -05:00
define_trace.h
perf.h	tracing: Add __cpumask to denote a trace event field that is a cpumask_t	2022-11-23 19:08:30 -05:00
syscall.h
trace_custom_events.h	tracing: Rename the staging files for trace_events	2022-04-02 08:40:04 -04:00
trace_events.h	tracing: Rename the staging files for trace_events	2022-04-02 08:40:04 -04:00