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If one wants to trace the name of the task that wakes up a process and pass that to the synthetic events, there's nothing currently that lets the synthetic events do that. Add a "common_comm" to the histogram logic that allows histograms save the current->comm as a variable that can be passed through and added to a synthetic event: # cd /sys/kernel/tracing # echo 's:wake_lat char[] waker; char[] wakee; u64 delta;' >> dynamic_events # echo 'hist:keys=pid:comm=common_comm:ts=common_timestamp.usecs if !(common_flags & 0x18)' > events/sched/sched_waking/trigger # echo 'hist:keys=next_pid:wake_comm=$comm:delta=common_timestamp.usecs-$ts:onmatch(sched.sched_waking).trace(wake_lat,$wake_comm,next_comm,$delta)' > events/sched/sched_switch/trigger The above will create a synthetic trace event that will save both the name of the waker and the wakee but only if the wakeup did not happen in a hard or soft interrupt context. The "common_comm" is used to save the task->comm at the time of the initial event and is passed via the "comm" variable to the second event, and that is saved as the "waker" field in the "wake_lat" synthetic event. Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Link: https://lore.kernel.org/20250407154912.3c6c6246@gandalf.local.home Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Reviewed-by: Tom Zanussi <zanussi@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>