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From: Steven Rostedt <rostedt@goodmis.org>
To: Petr Mladek <pmladek@suse.com>
Cc: linux-kernel@vger.kernel.org,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@kernel.org>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	Jiri Kosina <jikos@kernel.org>, Miroslav Benes <mbenes@suse.cz>,
	Jonathan Corbet <corbet@lwn.net>, Guo Ren <guoren@kernel.org>,
	"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>,
	Heiko Carstens <hca@linux.ibm.com>,
	Vasily Gorbik <gor@linux.ibm.com>,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Borislav Petkov <bp@alien8.de>,
	x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
	Kees Cook <keescook@chromium.org>,
	Anton Vorontsov <anton@enomsg.org>,
	Colin Cross <ccross@android.com>, Tony Luck <tony.luck@intel.com>,
	Joe Lawrence <joe.lawrence@redhat.com>,
	Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>,
	Mauro Carvalho Chehab <mchehab+huawei@kernel.org>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	linux-doc@vger.kernel.org, linux-csky@vger.kernel.org,
	linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
	linux-s390@vger.kernel.org, live-patching@vger.kernel.org
Subject: Re: [PATCH 11/11 v2.2] ftrace: Add recording of functions that caused recursion
Date: Tue, 3 Nov 2020 11:14:10 -0500	[thread overview]
Message-ID: <20201103111410.64feac6c@rorschach.local.home> (raw)
In-Reply-To: <20201103141043.GO20201@alley>

On Tue, 3 Nov 2020 15:10:43 +0100
Petr Mladek <pmladek@suse.com> wrote:

> BTW: What is actually the purpose of paranoid_test, please?
> 
> It prevents nested ftrace_record_recursion() calls on the same CPU
> (recursion, nesting from IRQ, NMI context).
> 
> Parallel calls from different CPUs are still possible:
> 
> CPU0					CPU1
> if (!atomic_read(&paranoid_test))	if (!atomic_read(&paranoid_test))
>    // passes				  // passes
>    atomic_inc(&paranoid_test);            atomic_inc(&paranoid_test);
> 
> 
> I do not see how a nested call could cause crash while a parallel
> one would be OK.
> 

Yeah, I should make that per cpu, but was lazy. ;-)

It was added at the end.

I'll update that to a per cpu, and local inc operations.

-- Steve

  reply	other threads:[~2020-11-03 16:14 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20201030213142.096102821@goodmis.org>
2020-10-30 21:31 ` [PATCH 06/11 v2] livepatch/ftrace: Add recursion protection to the ftrace callback Steven Rostedt
2020-10-30 21:31 ` [PATCH 07/11 v2] livepatch: Trigger WARNING if livepatch function fails due to recursion Steven Rostedt
2020-11-02 14:41   ` Petr Mladek
2020-11-02 16:56     ` Steven Rostedt
2020-10-30 21:31 ` [PATCH 11/11 v2] ftrace: Add recording of functions that caused recursion Steven Rostedt
2020-11-02 16:41   ` Petr Mladek
2020-11-02 17:09     ` Steven Rostedt
2020-11-02 17:19       ` Steven Rostedt
2020-11-03 10:40       ` Petr Mladek
2020-11-02 17:37     ` Steven Rostedt
2020-11-02 17:46       ` Steven Rostedt
2020-11-02 19:23         ` [PATCH 11/11 v2.2] " Steven Rostedt
2020-11-03 14:10           ` Petr Mladek
2020-11-03 16:14             ` Steven Rostedt [this message]
2020-11-04 19:13             ` Steven Rostedt
2020-11-02 19:14       ` [PATCH 11/11 v2.1] " Steven Rostedt

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