From: Steven Rostedt <rostedt@goodmis.org>
To: AKASHI Takahiro <takahiro.akashi@linaro.org>
Cc: Jungseok Lee <jungseoklee85@gmail.com>,
catalin.marinas@arm.com, will.deacon@arm.com, olof@lixom.net,
broonie@kernel.org, david.griego@linaro.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [RFC 2/3] arm64: refactor save_stack_trace()
Date: Wed, 15 Jul 2015 10:55:36 -0400 [thread overview]
Message-ID: <20150715105536.42949ea9@gandalf.local.home> (raw)
In-Reply-To: <55A646EE.6030402@linaro.org>
On Wed, 15 Jul 2015 20:41:34 +0900
AKASHI Takahiro <takahiro.akashi@linaro.org> wrote:
> Thank you for the explanation. But what I don't really understand here
> is why we need to add the "current function" to the stack dump list
> returned by save_stack_trace():
>
> In check_stack(),
> > /*
> > * Add the passed in ip from the function tracer.
> > * Searching for this on the stack will skip over
> > * most of the overhead from the stack tracer itself.
> > */
> > stack_dump_trace[0] = ip;
> > max_stack_trace.nr_entries++;
>
> I think that "ip" here is the "return address for func" in your
Ah, you are correct (for fentry).
> ascii art, and it should be already in the list if a frame is made
> by mcount (or func_call).
>
> In fact, stack tracer on arm64 works OK even without the patch[3/3]
> if the code quoted above is commented out.
> Even on x86, the code is conditional and not activated if the kernel
> is compiled without -mfentry before the following commit:
> commit 4df297129f62 ("tracing: Remove most or all of stack tracer stack size from stack_max_size")
>
> So what do I misunderstand here?
>
Hmm, I haven't touched the stack trace code in a while. With the added
stack frame for fentry, the hacks there are probably not needed.
I'll take a look at it and try to clean up the code.
Thanks,
-- Steve
WARNING: multiple messages have this Message-ID (diff)
From: rostedt@goodmis.org (Steven Rostedt)
To: linux-arm-kernel@lists.infradead.org
Subject: [RFC 2/3] arm64: refactor save_stack_trace()
Date: Wed, 15 Jul 2015 10:55:36 -0400 [thread overview]
Message-ID: <20150715105536.42949ea9@gandalf.local.home> (raw)
In-Reply-To: <55A646EE.6030402@linaro.org>
On Wed, 15 Jul 2015 20:41:34 +0900
AKASHI Takahiro <takahiro.akashi@linaro.org> wrote:
> Thank you for the explanation. But what I don't really understand here
> is why we need to add the "current function" to the stack dump list
> returned by save_stack_trace():
>
> In check_stack(),
> > /*
> > * Add the passed in ip from the function tracer.
> > * Searching for this on the stack will skip over
> > * most of the overhead from the stack tracer itself.
> > */
> > stack_dump_trace[0] = ip;
> > max_stack_trace.nr_entries++;
>
> I think that "ip" here is the "return address for func" in your
Ah, you are correct (for fentry).
> ascii art, and it should be already in the list if a frame is made
> by mcount (or func_call).
>
> In fact, stack tracer on arm64 works OK even without the patch[3/3]
> if the code quoted above is commented out.
> Even on x86, the code is conditional and not activated if the kernel
> is compiled without -mfentry before the following commit:
> commit 4df297129f62 ("tracing: Remove most or all of stack tracer stack size from stack_max_size")
>
> So what do I misunderstand here?
>
Hmm, I haven't touched the stack trace code in a while. With the added
stack frame for fentry, the hacks there are probably not needed.
I'll take a look at it and try to clean up the code.
Thanks,
-- Steve
next prev parent reply other threads:[~2015-07-15 14:55 UTC|newest]
Thread overview: 106+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-13 5:29 [RFC 0/3] arm64: ftrace: fix incorrect output from stack tracer AKASHI Takahiro
2015-07-13 5:29 ` AKASHI Takahiro
2015-07-13 5:29 ` [RFC 1/3] ftrace: adjust a function's pc to search for in check_stack() for arm64 AKASHI Takahiro
2015-07-13 5:29 ` AKASHI Takahiro
2015-07-13 15:24 ` Steven Rostedt
2015-07-13 15:24 ` Steven Rostedt
2015-07-15 0:22 ` AKASHI Takahiro
2015-07-15 0:22 ` AKASHI Takahiro
2015-07-13 5:29 ` [RFC 2/3] arm64: refactor save_stack_trace() AKASHI Takahiro
2015-07-13 5:29 ` AKASHI Takahiro
2015-07-14 12:47 ` Jungseok Lee
2015-07-14 12:47 ` Jungseok Lee
2015-07-14 13:31 ` Steven Rostedt
2015-07-14 13:31 ` Steven Rostedt
2015-07-15 0:20 ` AKASHI Takahiro
2015-07-15 0:20 ` AKASHI Takahiro
2015-07-15 2:51 ` Steven Rostedt
2015-07-15 2:51 ` Steven Rostedt
2015-07-15 11:41 ` AKASHI Takahiro
2015-07-15 11:41 ` AKASHI Takahiro
2015-07-15 14:55 ` Steven Rostedt [this message]
2015-07-15 14:55 ` Steven Rostedt
2015-07-15 16:13 ` Steven Rostedt
2015-07-15 16:13 ` Steven Rostedt
2015-07-16 0:27 ` AKASHI Takahiro
2015-07-16 0:27 ` AKASHI Takahiro
2015-07-16 1:08 ` AKASHI Takahiro
2015-07-16 1:08 ` AKASHI Takahiro
2015-07-16 1:38 ` Steven Rostedt
2015-07-16 1:38 ` Steven Rostedt
2015-07-17 10:46 ` Will Deacon
2015-07-17 10:46 ` Will Deacon
2015-07-16 13:29 ` Jungseok Lee
2015-07-16 13:29 ` Jungseok Lee
2015-07-16 13:54 ` Jungseok Lee
2015-07-16 13:54 ` Jungseok Lee
2015-07-16 14:24 ` Steven Rostedt
2015-07-16 14:24 ` Steven Rostedt
2015-07-16 15:01 ` Jungseok Lee
2015-07-16 15:01 ` Jungseok Lee
2015-07-16 15:31 ` Steven Rostedt
2015-07-16 15:31 ` Steven Rostedt
2015-07-16 15:52 ` Jungseok Lee
2015-07-16 15:52 ` Jungseok Lee
2015-07-16 20:22 ` Steven Rostedt
2015-07-16 20:22 ` Steven Rostedt
2015-07-17 2:49 ` AKASHI Takahiro
2015-07-17 2:49 ` AKASHI Takahiro
2015-07-17 3:21 ` Steven Rostedt
2015-07-17 3:21 ` Steven Rostedt
2015-07-16 16:16 ` Steven Rostedt
2015-07-16 16:16 ` Steven Rostedt
2015-07-17 12:40 ` Mark Rutland
2015-07-17 12:40 ` Mark Rutland
2015-07-17 12:51 ` Steven Rostedt
2015-07-17 12:51 ` Steven Rostedt
2015-07-17 13:00 ` Steven Rostedt
2015-07-17 13:00 ` Steven Rostedt
2015-07-17 14:28 ` Jungseok Lee
2015-07-17 14:28 ` Jungseok Lee
2015-07-17 14:41 ` Steven Rostedt
2015-07-17 14:41 ` Steven Rostedt
2015-07-17 14:59 ` Jungseok Lee
2015-07-17 14:59 ` Jungseok Lee
2015-07-17 15:34 ` Jungseok Lee
2015-07-17 15:34 ` Jungseok Lee
2015-07-17 16:01 ` Steven Rostedt
2015-07-17 16:01 ` Steven Rostedt
2015-07-20 16:20 ` Will Deacon
2015-07-20 16:20 ` Will Deacon
2015-07-20 23:53 ` AKASHI Takahiro
2015-07-20 23:53 ` AKASHI Takahiro
2015-07-21 10:26 ` AKASHI Takahiro
2015-07-21 10:26 ` AKASHI Takahiro
2015-07-21 14:34 ` Jungseok Lee
2015-07-21 14:34 ` Jungseok Lee
2015-08-03 9:09 ` Will Deacon
2015-08-03 9:09 ` Will Deacon
2015-08-03 14:01 ` Steven Rostedt
2015-08-03 14:01 ` Steven Rostedt
2015-08-03 14:04 ` Will Deacon
2015-08-03 14:04 ` Will Deacon
2015-08-03 16:30 ` Jungseok Lee
2015-08-03 16:30 ` Jungseok Lee
2015-08-03 16:57 ` Steven Rostedt
2015-08-03 16:57 ` Steven Rostedt
2015-08-03 17:22 ` Jungseok Lee
2015-08-03 17:22 ` Jungseok Lee
2015-08-03 17:32 ` Steven Rostedt
2015-08-03 17:32 ` Steven Rostedt
2015-08-04 7:41 ` AKASHI Takahiro
2015-08-04 7:41 ` AKASHI Takahiro
2015-07-17 2:04 ` AKASHI Takahiro
2015-07-17 2:04 ` AKASHI Takahiro
2015-07-17 14:38 ` Jungseok Lee
2015-07-17 14:38 ` Jungseok Lee
2015-07-16 14:28 ` Mark Rutland
2015-07-16 14:28 ` Mark Rutland
2015-07-16 14:34 ` Steven Rostedt
2015-07-16 14:34 ` Steven Rostedt
2015-07-17 2:09 ` AKASHI Takahiro
2015-07-17 2:09 ` AKASHI Takahiro
2015-07-13 5:29 ` [RFC 3/3] arm64: ftrace: mcount() should not create a stack frame AKASHI Takahiro
2015-07-13 5:29 ` AKASHI Takahiro
2015-07-13 15:01 ` [RFC 0/3] arm64: ftrace: fix incorrect output from stack tracer Jungseok Lee
2015-07-13 15:01 ` Jungseok Lee
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