From: 王贇 <yun.wang@linux.alibaba.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: 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>, Miroslav Benes <mbenes@suse.cz>,
Petr Mladek <pmladek@suse.com>,
Joe Lawrence <joe.lawrence@redhat.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 v6 1/2] ftrace: disable preemption when recursion locked
Date: Wed, 27 Oct 2021 11:09:29 +0800 [thread overview]
Message-ID: <e8bb4220-4895-e55d-4aea-cdd265fdfd38@linux.alibaba.com> (raw)
In-Reply-To: <20211026225552.72a7ee79@rorschach.local.home>
On 2021/10/27 上午10:55, Steven Rostedt wrote:
> On Wed, 27 Oct 2021 10:34:13 +0800
> 王贇 <yun.wang@linux.alibaba.com> wrote:
>
>> +/*
>> + * Preemption will be enabled (if it was previously enabled).
>> + */
>> static __always_inline void trace_clear_recursion(int bit)
>> {
>> + WARN_ON_ONCE(bit < 0);
>
> Can you send a v7 without the WARN_ON.
>
> This is an extremely hot path, and this will cause noticeable overhead.
>
> If something were to call this with bit < 0, then it would crash and
> burn rather quickly.
I see, if the problem will be notified anyway then it's fine, v7 on the way.
Regards,
Michael Wang
>
> -- Steve
>
>
>> +
>> + preempt_enable_notrace();
>> barrier();
>> trace_recursion_clear(bit);
>> }
next prev parent reply other threads:[~2021-10-27 3:09 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-27 2:32 [PATCH v6 0/2] fix & prevent the missing preemption disabling 王贇
2021-10-27 2:34 ` [PATCH v6 1/2] ftrace: disable preemption when recursion locked 王贇
2021-10-27 2:55 ` Steven Rostedt
2021-10-27 3:09 ` 王贇 [this message]
2021-10-27 2:34 ` [PATCH v6 2/2] ftrace: do CPU checking after preemption disabled 王贇
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