From: Steven Rostedt <rostedt@goodmis.org>
To: Petr Mladek <pmladek@suse.com>
Cc: 王贇 <yun.wang@linux.alibaba.com>, "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>,
"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: Thu, 14 Oct 2021 23:39:07 -0400 [thread overview]
Message-ID: <20211014233907.15f13f62@oasis.local.home> (raw)
In-Reply-To: <YWhJP41cNwDphYsv@alley>
On Thu, 14 Oct 2021 17:14:07 +0200
Petr Mladek <pmladek@suse.com> wrote:
> /**
> * ftrace_test_recursion_trylock - tests for recursion in same context
> *
> * Use this for ftrace callbacks. This will detect if the function
> * tracing recursed in the same context (normal vs interrupt),
> *
> * Returns: -1 if a recursion happened.
> - * >= 0 if no recursion
> + * >= 0 if no recursion (success)
> + *
> + * Disables the preemption on success. It is just for a convenience.
> + * Current users needed to disable the preemtion for some reasons.
> */
I started replying to this explaining the difference between bit not
zero and a bit zero, and I think I found a design flaw that can allow
unwanted recursion.
It's late and I'm about to go to bed, but I may have a new patch to fix
this before this gets added, as the fix will conflict with this patch,
and the fix will likely need to go to stable.
Stay tuned.
-- Steve
next prev parent reply other threads:[~2021-10-15 3:39 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
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 [this message]
2021-10-13 8:52 ` [PATCH v3 2/2] ftrace: do CPU checking after preemption disabled 王贇
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