live-patching.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: 王贇 <yun.wang@linux.alibaba.com>
To: Miroslav Benes <mbenes@suse.cz>
Cc: Guo Ren <guoren@kernel.org>, Steven Rostedt <rostedt@goodmis.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: Wed, 13 Oct 2021 09:50:17 +0800	[thread overview]
Message-ID: <74090798-7d93-0713-982c-6f0247118d20@linux.alibaba.com> (raw)
In-Reply-To: <alpine.LSU.2.21.2110121421260.3394@pobox.suse.cz>



On 2021/10/12 下午8:24, Miroslav Benes wrote:
[snip]
>>
>>  	func = list_first_or_null_rcu(&ops->func_stack, struct klp_func,
>>  				      stack_node);
>> @@ -120,7 +115,6 @@ static void notrace klp_ftrace_handler(unsigned long ip,
>>  	klp_arch_set_pc(fregs, (unsigned long)func->new_func);
>>
>>  unlock:
>> -	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).

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

Regards,
Michael Wang

> 
> Miroslav
> 

  parent reply	other threads:[~2021-10-13  1:51 UTC|newest]

Thread overview: 24+ 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  5:40 ` [PATCH 1/2] ftrace: disable preemption on the testing of recursion 王贇
2021-10-12 12:17   ` Steven Rostedt
2021-10-13  1:46     ` 王贇
2021-10-12 12:24   ` Miroslav Benes
2021-10-12 12:29     ` Steven Rostedt
2021-10-13  1:52       ` 王贇
2021-10-13  1:50     ` 王贇 [this message]
2021-10-13  2:27       ` Steven Rostedt
2021-10-13  2:36         ` 王贇
2021-10-12 12:43   ` Steven Rostedt
2021-10-13  2:04     ` 王贇
2021-10-13  2:30       ` Steven Rostedt
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 11:20   ` Peter Zijlstra
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
2021-10-13  3:16 ` [PATCH v2 0/2] fix & prevent the missing preemption disabling 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  3:18   ` [PATCH v2 2/2] ftrace: do CPU checking after preemption disabled 王贇
2021-10-13  3:26   ` [PATCH v2 0/2] fix & prevent the missing preemption disabling Steven Rostedt
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

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=74090798-7d93-0713-982c-6f0247118d20@linux.alibaba.com \
    --to=yun.wang@linux.alibaba.com \
    --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=rostedt@goodmis.org \
    --cc=tglx@linutronix.de \
    --cc=x86@kernel.org \
    --subject='Re: [PATCH 1/2] ftrace: disable preemption on the testing of recursion' \
    /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

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).