All of lore.kernel.org
 help / color / mirror / Atom feed
From: Steven Rostedt <rostedt@goodmis.org>
To: 王贇 <yun.wang@linux.alibaba.com>
Cc: Miroslav Benes <mbenes@suse.cz>, Guo Ren <guoren@kernel.org>,
	Ingo Molnar <mingo@redhat.com>,
	"James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>,
	Helge Deller <deller@gmx.de>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Paul Mackerras <paulus@samba.org>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Thomas Gleixner <tglx@linutronix.de>,
	Borislav Petkov <bp@alien8.de>,
	x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	Jiri Kosina <jikos@kernel.org>, Petr Mladek <pmladek@suse.com>,
	Joe Lawrence <joe.lawrence@redhat.com>,
	Colin Ian King <colin.king@canonical.com>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	"Peter Zijlstra (Intel)" <peterz@infradead.org>,
	Nicholas Piggin <npiggin@gmail.com>,
	Jisheng Zhang <jszhang@kernel.org>,
	linux-csky@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
	linux-riscv@lists.infradead.org, live-patching@vger.kernel.org
Subject: Re: [PATCH 1/2] ftrace: disable preemption on the testing of recursion
Date: Tue, 12 Oct 2021 22:27:58 -0400	[thread overview]
Message-ID: <20211012222758.1a029157@oasis.local.home> (raw)
In-Reply-To: <74090798-7d93-0713-982c-6f0247118d20@linux.alibaba.com>

On Wed, 13 Oct 2021 09:50:17 +0800
王贇 <yun.wang@linux.alibaba.com> wrote:

> >> -	preempt_enable_notrace();
> >>  	ftrace_test_recursion_unlock(bit);
> >>  }  
> > 
> > I don't like this change much. We have preempt_disable there not because 
> > of ftrace_test_recursion, but because of RCU. ftrace_test_recursion was 
> > added later. Yes, it would work with the change, but it would also hide 
> > things which should not be hidden in my opinion.  
> 
> Not very sure about the backgroup stories, but just found this in
> 'Documentation/trace/ftrace-uses.rst':
> 
>   Note, on success,
>   ftrace_test_recursion_trylock() will disable preemption, and the
>   ftrace_test_recursion_unlock() will enable it again (if it was previously
>   enabled).

Right that part is to be fixed by what you are adding here.

The point that Miroslav is complaining about is that the preemption
disabling is special in this case, and not just from the recursion
point of view, which is why the comment is still required.

-- Steve


> 
> Seems like this lock pair was supposed to take care the preemtion itself?

WARNING: multiple messages have this Message-ID (diff)
From: Steven Rostedt <rostedt@goodmis.org>
To: 王贇 <yun.wang@linux.alibaba.com>
Cc: Miroslav Benes <mbenes@suse.cz>, Guo Ren <guoren@kernel.org>,
	Ingo Molnar <mingo@redhat.com>,
	"James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>,
	Helge Deller <deller@gmx.de>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Paul Mackerras <paulus@samba.org>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Thomas Gleixner <tglx@linutronix.de>,
	Borislav Petkov <bp@alien8.de>,
	x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	Jiri Kosina <jikos@kernel.org>, Petr Mladek <pmladek@suse.com>,
	Joe Lawrence <joe.lawrence@redhat.com>,
	Colin Ian King <colin.king@canonical.com>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	"Peter Zijlstra (Intel)" <peterz@infradead.org>,
	Nicholas Piggin <npiggin@gmail.com>,
	Jisheng Zhang <jszhang@kernel.org>,
	linux-csky@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
	linux-riscv@lists.infradead.org, live-patching@vger.kernel.org
Subject: Re: [PATCH 1/2] ftrace: disable preemption on the testing of recursion
Date: Tue, 12 Oct 2021 22:27:58 -0400	[thread overview]
Message-ID: <20211012222758.1a029157@oasis.local.home> (raw)
In-Reply-To: <74090798-7d93-0713-982c-6f0247118d20@linux.alibaba.com>

On Wed, 13 Oct 2021 09:50:17 +0800
王贇 <yun.wang@linux.alibaba.com> wrote:

> >> -	preempt_enable_notrace();
> >>  	ftrace_test_recursion_unlock(bit);
> >>  }  
> > 
> > I don't like this change much. We have preempt_disable there not because 
> > of ftrace_test_recursion, but because of RCU. ftrace_test_recursion was 
> > added later. Yes, it would work with the change, but it would also hide 
> > things which should not be hidden in my opinion.  
> 
> Not very sure about the backgroup stories, but just found this in
> 'Documentation/trace/ftrace-uses.rst':
> 
>   Note, on success,
>   ftrace_test_recursion_trylock() will disable preemption, and the
>   ftrace_test_recursion_unlock() will enable it again (if it was previously
>   enabled).

Right that part is to be fixed by what you are adding here.

The point that Miroslav is complaining about is that the preemption
disabling is special in this case, and not just from the recursion
point of view, which is why the comment is still required.

-- Steve


> 
> Seems like this lock pair was supposed to take care the preemtion itself?

_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

WARNING: multiple messages have this Message-ID (diff)
From: Steven Rostedt <rostedt@goodmis.org>
To: 王贇 <yun.wang@linux.alibaba.com>
Cc: "Peter Zijlstra \(Intel\)" <peterz@infradead.org>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	"James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>,
	Guo Ren <guoren@kernel.org>, Jisheng Zhang <jszhang@kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	live-patching@vger.kernel.org, linux-riscv@lists.infradead.org,
	Miroslav Benes <mbenes@suse.cz>,
	Paul Mackerras <paulus@samba.org>,
	Joe Lawrence <joe.lawrence@redhat.com>,
	Helge Deller <deller@gmx.de>,
	x86@kernel.org, linux-csky@vger.kernel.org,
	Ingo Molnar <mingo@redhat.com>, Petr Mladek <pmladek@suse.com>,
	Albert Ou <aou@eecs.berkeley.edu>, Jiri Kosina <jikos@kernel.org>,
	Nicholas Piggin <npiggin@gmail.com>,
	Borislav Petkov <bp@alien8.de>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	linux-parisc@vger.kernel.org, linux-kernel@vger.kernel.org,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Colin Ian King <colin.king@canonical.com>,
	linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH 1/2] ftrace: disable preemption on the testing of recursion
Date: Tue, 12 Oct 2021 22:27:58 -0400	[thread overview]
Message-ID: <20211012222758.1a029157@oasis.local.home> (raw)
In-Reply-To: <74090798-7d93-0713-982c-6f0247118d20@linux.alibaba.com>

On Wed, 13 Oct 2021 09:50:17 +0800
王贇 <yun.wang@linux.alibaba.com> wrote:

> >> -	preempt_enable_notrace();
> >>  	ftrace_test_recursion_unlock(bit);
> >>  }  
> > 
> > I don't like this change much. We have preempt_disable there not because 
> > of ftrace_test_recursion, but because of RCU. ftrace_test_recursion was 
> > added later. Yes, it would work with the change, but it would also hide 
> > things which should not be hidden in my opinion.  
> 
> Not very sure about the backgroup stories, but just found this in
> 'Documentation/trace/ftrace-uses.rst':
> 
>   Note, on success,
>   ftrace_test_recursion_trylock() will disable preemption, and the
>   ftrace_test_recursion_unlock() will enable it again (if it was previously
>   enabled).

Right that part is to be fixed by what you are adding here.

The point that Miroslav is complaining about is that the preemption
disabling is special in this case, and not just from the recursion
point of view, which is why the comment is still required.

-- Steve


> 
> Seems like this lock pair was supposed to take care the preemtion itself?

  reply	other threads:[~2021-10-13  2:28 UTC|newest]

Thread overview: 65+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-12  5:39 [PATCH 0/2] ftrace: make sure preemption disabled on recursion testing 王贇
2021-10-12  5:39 ` 王贇
2021-10-12  5:40 ` [PATCH 1/2] ftrace: disable preemption on the testing of recursion 王贇
2021-10-12  5:40   ` 王贇
2021-10-12 12:17   ` Steven Rostedt
2021-10-12 12:17     ` Steven Rostedt
2021-10-12 12:17     ` Steven Rostedt
2021-10-13  1:46     ` 王贇
2021-10-13  1:46       ` 王贇
2021-10-13  1:46       ` 王贇
2021-10-12 12:24   ` Miroslav Benes
2021-10-12 12:24     ` Miroslav Benes
2021-10-12 12:24     ` Miroslav Benes
2021-10-12 12:29     ` Steven Rostedt
2021-10-12 12:29       ` Steven Rostedt
2021-10-12 12:29       ` Steven Rostedt
2021-10-13  1:52       ` 王贇
2021-10-13  1:52         ` 王贇
2021-10-13  1:52         ` 王贇
2021-10-13  1:50     ` 王贇
2021-10-13  1:50       ` 王贇
2021-10-13  1:50       ` 王贇
2021-10-13  2:27       ` Steven Rostedt [this message]
2021-10-13  2:27         ` Steven Rostedt
2021-10-13  2:27         ` Steven Rostedt
2021-10-13  2:36         ` 王贇
2021-10-13  2:36           ` 王贇
2021-10-13  2:36           ` 王贇
2021-10-12 12:43   ` Steven Rostedt
2021-10-12 12:43     ` Steven Rostedt
2021-10-12 12:43     ` Steven Rostedt
2021-10-13  2:04     ` 王贇
2021-10-13  2:04       ` 王贇
2021-10-13  2:04       ` 王贇
2021-10-13  2:30       ` Steven Rostedt
2021-10-13  2:30         ` Steven Rostedt
2021-10-13  2:30         ` Steven Rostedt
2021-10-13  2:38         ` 王贇
2021-10-13  2:38           ` 王贇
2021-10-13  2:38           ` 王贇
2021-10-12  5:40 ` [PATCH 2/2] ftrace: prevent preemption in perf_ftrace_function_call() 王贇
2021-10-12  5:40   ` 王贇
2021-10-12 11:20   ` Peter Zijlstra
2021-10-12 11:20     ` Peter Zijlstra
2021-10-12 11:20     ` Peter Zijlstra
2021-10-13  1:45     ` 王贇
2021-10-13  1:45       ` 王贇
2021-10-13  1:45       ` 王贇
2021-10-12  5:41 ` [PATCH 0/2] ftrace: make sure preemption disabled on recursion testing 王贇
2021-10-12  5:41   ` 王贇
2021-10-13  3:16 ` [PATCH v2 0/2] fix & prevent the missing preemption disabling 王贇
2021-10-13  3:16   ` 王贇
2021-10-13  3:17   ` [PATCH v2 1/2] ftrace: disable preemption between ftrace_test_recursion_trylock/unlock() 王贇
2021-10-13  3:17     ` 王贇
2021-10-13  3:18   ` [PATCH v2 2/2] ftrace: do CPU checking after preemption disabled 王贇
2021-10-13  3:18     ` 王贇
2021-10-13  3:26   ` [PATCH v2 0/2] fix & prevent the missing preemption disabling Steven Rostedt
2021-10-13  3:26     ` Steven Rostedt
2021-10-13  3:26     ` Steven Rostedt
2021-10-13  3:33     ` 王贇
2021-10-13  3:33       ` 王贇
2021-10-13  3:33       ` 王贇
2021-10-26 23:48 ` [PATCH 0/2] ftrace: make sure preemption disabled on recursion testing Palmer Dabbelt
2021-10-26 23:48   ` Palmer Dabbelt
2021-10-26 23:48   ` Palmer Dabbelt

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20211012222758.1a029157@oasis.local.home \
    --to=rostedt@goodmis.org \
    --cc=James.Bottomley@HansenPartnership.com \
    --cc=aou@eecs.berkeley.edu \
    --cc=benh@kernel.crashing.org \
    --cc=bp@alien8.de \
    --cc=colin.king@canonical.com \
    --cc=deller@gmx.de \
    --cc=guoren@kernel.org \
    --cc=hpa@zytor.com \
    --cc=jikos@kernel.org \
    --cc=joe.lawrence@redhat.com \
    --cc=jpoimboe@redhat.com \
    --cc=jszhang@kernel.org \
    --cc=linux-csky@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-parisc@vger.kernel.org \
    --cc=linux-riscv@lists.infradead.org \
    --cc=linuxppc-dev@lists.ozlabs.org \
    --cc=live-patching@vger.kernel.org \
    --cc=mbenes@suse.cz \
    --cc=mhiramat@kernel.org \
    --cc=mingo@redhat.com \
    --cc=mpe@ellerman.id.au \
    --cc=npiggin@gmail.com \
    --cc=palmer@dabbelt.com \
    --cc=paul.walmsley@sifive.com \
    --cc=paulus@samba.org \
    --cc=peterz@infradead.org \
    --cc=pmladek@suse.com \
    --cc=tglx@linutronix.de \
    --cc=x86@kernel.org \
    --cc=yun.wang@linux.alibaba.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.