From: 王贇 <yun.wang@linux.alibaba.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: 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>,
Steven Rostedt <rostedt@goodmis.org>,
Borislav Petkov <bp@alien8.de>,
Nicholas Piggin <npiggin@gmail.com>,
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 2/2] ftrace: prevent preemption in perf_ftrace_function_call()
Date: Wed, 13 Oct 2021 09:45:45 +0800 [thread overview]
Message-ID: <1193d016-ec4d-2b29-4d33-5a04ca85c14d@linux.alibaba.com> (raw)
In-Reply-To: <YWVvfBybqjKuifum@hirez.programming.kicks-ass.net>
On 2021/10/12 下午7:20, Peter Zijlstra wrote:
> On Tue, Oct 12, 2021 at 01:40:31PM +0800, 王贇 wrote:
>
>> diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c
>> index 6aed10e..33c2f76 100644
>> --- a/kernel/trace/trace_event_perf.c
>> +++ b/kernel/trace/trace_event_perf.c
>> @@ -441,12 +441,19 @@ void perf_trace_buf_update(void *record, u16 type)
>> if (!rcu_is_watching())
>> return;
>>
>> + /*
>> + * Prevent CPU changing from now on. rcu must
>> + * be in watching if the task was migrated and
>> + * scheduled.
>> + */
>> + preempt_disable_notrace();
>> +
>> if ((unsigned long)ops->private != smp_processor_id())
>> - return;
>> + goto out;
>>
>> bit = ftrace_test_recursion_trylock(ip, parent_ip);
>> if (bit < 0)
>> - return;
>> + goto out;
>>
>> event = container_of(ops, struct perf_event, ftrace_ops);
>>
>
> This seems rather daft, wouldn't it be easier to just put that check
> under the recursion thing?
In case if the condition matched, extra lock/unlock will be introduced,
but I guess that's acceptable since this seems unlikely to happen :-P
Will move the check in v2.
Regards,
Michael Wang
>
next prev parent reply other threads:[~2021-10-13 1:47 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
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 [this message]
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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