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Date: Wed, 10 Jun 2026 10:00:22 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Imran Khan <imran.f.khan@oracle.com>
Cc: rostedt@goodmis.org, mhiramat@kernel.org,
	mathieu.desnoyers@efficios.com, linux-trace-kernel@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] task_work: add tracepoints for task_work callbacks
Message-ID: <20260610080022.GD48970@noisy.programming.kicks-ass.net>
References: <20260610041408.2461637-1-imran.f.khan@oracle.com>
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In-Reply-To: <20260610041408.2461637-1-imran.f.khan@oracle.com>

On Wed, Jun 10, 2026 at 12:14:08PM +0800, Imran Khan wrote:
> task_work tracepoints can be enabled by:
> 
>     echo 1 > /sys/kernel/tracing/events/task_work/enable
> 
> and trace logs would look like:
> 
>     ... task_work_add_request: target_comm=ls target_pid=227 work=ffff95d20641a508 func=____fput notify=TWA_RESUME
>     ... task_work_add_done: target_comm=ls target_pid=227 work=ffff95d20641a508 ret=0
>     ... task_work_add_request: target_comm=ls target_pid=227 work=ffff95d20641a5c8 func=____fput notify=TWA_RESUME
>     ... task_work_add_done: target_comm=ls target_pid=227 work=ffff95d20641a5c8 ret=0
>     ... task_work_add_request: target_comm=ls target_pid=227 work=ffff95d20641a688 func=____fput notify=TWA_RESUME
>     ... task_work_add_done: target_comm=ls target_pid=227 work=ffff95d20641a688 ret=0
>     ... task_work_add_request: target_comm=ls target_pid=227 work=ffff95d20641a748 func=____fput notify=TWA_RESUME
>     ... task_work_add_done: target_comm=ls target_pid=227 work=ffff95d20641a748 ret=0
>     ... task_work_run_start: comm=ls pid=227 work=ffff95d20641a748 func=____fput
>     ... task_work_run_end: comm=ls pid=227 work=ffff95d20641a748 func=____fput
>     ... task_work_run_start: comm=ls pid=227 work=ffff95d20641a688 func=____fput
>     ... task_work_run_end: comm=ls pid=227 work=ffff95d20641a688 func=____fput
>     ... task_work_run_start: comm=ls pid=227 work=ffff95d20641a5c8 func=____fput
>     ... task_work_run_end: comm=ls pid=227 work=ffff95d20641a5c8 func=____fput
>     ... task_work_run_start: comm=ls pid=227 work=ffff95d20641a508 func=____fput
>     ... task_work_run_end: comm=ls pid=227 work=ffff95d20641a508 func=____fput
> 
> formatted as:
>     target_comm=<comm of target task>
>     target_pid=<pid of target task>
>     work=<callback_head *>
>     func=<callback_head->func>
>     notify=<way to notify the target task>
>     comm=<comm of current task executing func>
>     pid=<pid of current task executing func>

And not a single justification for all this nonsense :-( So much ugly
and no gain...