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From: David Howells <dhowells@redhat.com>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: dhowells@redhat.com,
	syzbot <syzbot+1e0edc4b8b7494c28450@syzkaller.appspotmail.com>,
	Eric Biggers <ebiggers@kernel.org>,
	David Miller <davem@davemloft.net>,
	linux-afs@lists.infradead.org,
	LKML <linux-kernel@vger.kernel.org>,
	netdev <netdev@vger.kernel.org>,
	syzkaller-bugs <syzkaller-bugs@googlegroups.com>
Subject: Re: kernel BUG at net/rxrpc/local_object.c:LINE!
Date: Tue, 13 Aug 2019 16:06:50 +0100	[thread overview]
Message-ID: <8013.1565708810@warthog.procyon.org.uk> (raw)
In-Reply-To: <CACT4Y+YCB3o5Ps9RNq9KpMcmGCwBM4R9DeX67prQ9Q3UppGowQ@mail.gmail.com>

Dmitry Vyukov <dvyukov@google.com> wrote:

> > I meant that I don't know how to turn a tracepoint on from inside the kernel.
> 
> This /sys/kernel/debug/tracing/events/rxrpc/rxrpc_local/enable in:
>         echo 1 > /sys/kernel/debug/tracing/events/rxrpc/rxrpc_local/enable
> should map to some global variable, right? If so, it should be
> possible to initialize that var to 1 statically. Or that won't work
> for some reason?

As I understand it, it's all hidden inside of tracing macros and ftrace
infrastructure and involves runtime patching the code to enable tracepoints
(they're effectively NOP'ed out when not in use).

So, no, it's not that simple.

I asked Steven and he says:

	trace_set_clr_event("sched", "sched_switch", 1);

is the same as

	echo 1 > events/sched/sched_switch/enable

So it can be done.  Will syzbot actually collect the trace log?

David

  parent reply	other threads:[~2019-08-13 15:06 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-28  2:47 kernel BUG at net/rxrpc/local_object.c:LINE! syzbot
2019-07-02 13:37 ` David Howells
2019-07-05 12:12   ` Dmitry Vyukov
2019-07-05 12:15     ` Dmitry Vyukov
2019-07-06 10:03     ` syzbot
2019-07-31 14:30   ` David Howells
2019-07-31 14:46     ` Dmitry Vyukov
2019-07-31 15:19     ` David Howells
2019-07-31 15:31       ` Dmitry Vyukov
2019-08-13 14:23       ` David Howells
2019-08-13 14:28         ` Dmitry Vyukov
2019-08-13 15:06         ` David Howells [this message]
2019-08-13 15:12           ` Dmitry Vyukov
2019-08-13 15:29           ` David Howells
2019-08-18 18:47 ` syzbot
     [not found] <20190819071101.5796-1-hdanton@sina.com>
2019-08-19  8:23 ` David Howells

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