From: 王贇 <yun.wang@linux.alibaba.com>
To: Petr Mladek <pmladek@suse.com>
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>, Miroslav Benes <mbenes@suse.cz>,
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 v3 1/2] ftrace: disable preemption between ftrace_test_recursion_trylock/unlock()
Date: Fri, 15 Oct 2021 12:45:27 +0800 [thread overview]
Message-ID: <a5bae9a5-9ab7-2660-caa6-facecb1dba32@linux.alibaba.com> (raw)
In-Reply-To: <5e907ed3-806b-b0e5-518d-d2f3b265377f@linux.alibaba.com>
On 2021/10/15 上午11:13, 王贇 wrote:
[snip]
>> # define do_ftrace_record_recursion(ip, pip) do { } while (0)
>> #endif
>>
>> +/*
>> + * trace_test_and_set_recursion() is called on several layers
>> + * of the ftrace code when handling the same ftrace entry.
>> + * These calls might be nested/recursive.
>> + *
>> + * It uses TRACE_LIST_*BITs to distinguish between this
>> + * internal recursion and recursion caused by calling
>> + * the traced function by the ftrace code.
>> + *
>> + * Returns: > 0 when no recursion
>> + * 0 when called recursively internally (safe)
>
> The 0 can also happened when ftrace handler recursively called trylock()
> under the same context, or not?
>
Never mind... you're right about this.
Regards,
Michael Wang
> Regards,
> Michael Wang
>
>> + * -1 when the traced function was called recursively from
>> + * the ftrace handler (unsafe)
>> + */
>> static __always_inline int trace_test_and_set_recursion(unsigned long ip, unsigned long pip,
>> int start, int max)
>> {
>> unsigned int val = READ_ONCE(current->trace_recursion);
>> int bit;
>>
>> - /* A previous recursion check was made */
>> + /* Called recursively internally by different ftrace code layers? */
>> if ((val & TRACE_CONTEXT_MASK) > max)
>> return 0;
>
>>
>>
next prev parent reply other threads:[~2021-10-15 4:45 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-13 8:51 [PATCH v3 0/2] fix & prevent the missing preemption disabling 王贇
2021-10-13 8:51 ` [PATCH v3 1/2] ftrace: disable preemption between ftrace_test_recursion_trylock/unlock() 王贇
2021-10-14 9:13 ` Miroslav Benes
2021-10-14 9:22 ` 王贇
2021-10-14 13:28 ` Steven Rostedt
2021-10-14 15:14 ` Petr Mladek
2021-10-15 3:13 ` 王贇
2021-10-15 4:45 ` 王贇 [this message]
2021-10-15 7:28 ` Petr Mladek
2021-10-15 9:12 ` 王贇
2021-10-15 13:35 ` Steven Rostedt
2021-10-15 3:39 ` Steven Rostedt
2021-10-13 8:52 ` [PATCH v3 2/2] ftrace: do CPU checking after preemption disabled 王贇
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