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([240d:1a:13a:f00:4b94:68e0:2d8b:3983]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-71b264bec57sm9220291b3a.69.2024.10.01.23.43.29 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 01 Oct 2024 23:43:31 -0700 (PDT) Message-ID: Date: Wed, 2 Oct 2024 15:43:35 +0900 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] ftrace: Hide a extra entry in stack trace To: Steven Rostedt Cc: "Masami Hiramatsu (Google)" , Mathieu Desnoyers , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org References: <20240926061311.25625-1-tatsuya.s2862@gmail.com> <20240930085139.5d34f28236a67ef1e9143655@kernel.org> <509829ab-98b5-4429-ba59-e1fc7b300682@gmail.com> <20241001094742.1282d2ad@gandalf.local.home> Content-Language: en-US From: Tatsuya S In-Reply-To: <20241001094742.1282d2ad@gandalf.local.home> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 10/1/24 10:47 PM, Steven Rostedt wrote: > On Tue, 1 Oct 2024 22:27:03 +0900 > ts wrote: > >>> ... >>> sh-140 [001] ...1. 18.352601: myevent: (vfs_write+0x4/0x560) >>> sh-140 [001] ...1. 18.352602: >>> => ksys_write >>> => do_syscall_64 >>> => entry_SYSCALL_64_after_hwframe >>> sh-140 [001] ...1. 18.352602: vfs_write <-ksys_write >>> sh-140 [001] ...1. 18.352604: >>> => ftrace_regs_call >>> => vfs_write >>> => ksys_write >>> => do_syscall_64 >>> => entry_SYSCALL_64_after_hwframe >>> ------ >>> As you can see, myevent skips "vfs_write". >>> (and function tracer still have ftrace_regs_call() ) >> >> Thanks for the other tests. This issue may be function_trace_call() >> specific problem. >> >> So I will change the place to increment skip number. > > My fear is that we are going to just break it elsewhere. The problem with > the "skip" is that there's so many configurations when we get here, we may > not really know what to skip. If the compiler inlines something, then we > may skip something we do not want to. > > I rather have extra information than not enough. > > -- Steve It may not be clean and be bit redundant, but I think it would be more maintainable to treat "skip(and skipped functions)" separately only at the top(parent) of functions that display stack trace. thanks.