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
>
next prev 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
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