From: Masami Hiramatsu <mhiramat@redhat.com>
To: "Frédéric Weisbecker" <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>, Steven Rostedt <rostedt@goodmis.org>,
lkml <linux-kernel@vger.kernel.org>,
systemtap <systemtap@sources.redhat.com>,
kvm <kvm@vger.kernel.org>,
Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Subject: Re: [PATCH -tip v5 4/7] tracing: add kprobe-based event tracer
Date: Sat, 09 May 2009 17:33:00 -0000 [thread overview]
Message-ID: <4A05BE81.8070306@redhat.com> (raw)
In-Reply-To: <c62985530905090936v22f6ab1s867d8f8d6a74b95a@mail.gmail.com>
Frédéric Weisbecker wrote:
> Hi,
>
> 2009/5/9 Masami Hiramatsu <mhiramat@redhat.com>:
[...]
>> +
>> +/* event recording functions */
>> +static void kprobe_trace_record(unsigned long ip, struct trace_probe *tp,
>> + struct pt_regs *regs)
>> +{
>> + __trace_bprintk(ip, "%s%s%+ld\n",
>> + probe_is_return(tp) ? "<-" : "@",
>> + probe_symbol(tp), probe_offset(tp));
>> +}
>
>
>
> What happens here if you have:
>
> kprobe_trace_record() {
> probe_symbol() {
> .... probes_open() {
> cleanup_all_probes() {
> free_trace_probe();
> return tp->symbol ? ....; //crack!
>
> I wonder if you shouldn't use a per_cpu list of probes,
> spinlocked/irqsaved accessed
> and also a kind of prevention against nmi.
Sure, cleanup_all_probes() invokes unregister_kprobe() via
unregister_trace_probe(), which waits running probe-handlers by
using synchronize_sched()(because kprobes disables preemption
around its handlers), before free_trace_probe().
So you don't need any locks there :-)
Thank you,
--
Masami Hiramatsu
Software Engineer
Hitachi Computer Products (America) Inc.
Software Solutions Division
e-mail: mhiramat@redhat.com
next prev parent reply other threads:[~2009-05-09 17:33 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-05-09 0:46 [PATCH -tip v5 0/7] tracing: kprobe-based event tracer and x86 instruction decoder Masami Hiramatsu
2009-05-09 0:46 ` [PATCH -tip v5 1/7] x86: instruction decorder API Masami Hiramatsu
2009-05-11 9:27 ` Christoph Hellwig
2009-05-11 14:35 ` Masami Hiramatsu
2009-05-13 8:23 ` Gleb Natapov
2009-05-13 9:35 ` Przemysław Pawełczyk
2009-05-13 9:43 ` Gleb Natapov
2009-05-13 14:34 ` Masami Hiramatsu
2009-05-13 15:20 ` Gleb Natapov
2009-05-09 0:47 ` [PATCH -tip v5 2/7] kprobes: checks probe address is instruction boudary on x86 Masami Hiramatsu
2009-05-11 14:20 ` Steven Rostedt
2009-05-11 14:59 ` Masami Hiramatsu
2009-05-11 15:12 ` Masami Hiramatsu
2009-05-11 15:22 ` Steven Rostedt
2009-05-11 18:19 ` Masami Hiramatsu
2009-05-09 0:47 ` [PATCH -tip v5 3/7] kprobes: cleanup fix_riprel() using insn decoder " Masami Hiramatsu
2009-05-09 1:16 ` [PATCH -tip v5 6/7] x86: add pt_regs register and stack access APIs Masami Hiramatsu
2009-05-09 1:16 ` [PATCH -tip v5 5/7] x86: fix kernel_trap_sp() Masami Hiramatsu
2009-05-11 9:28 ` Christoph Hellwig
2009-05-11 13:47 ` Masami Hiramatsu
2009-05-09 1:16 ` [PATCH -tip v5 4/7] tracing: add kprobe-based event tracer Masami Hiramatsu
2009-05-09 16:36 ` Frédéric Weisbecker
2009-05-09 17:33 ` Masami Hiramatsu [this message]
2009-05-11 21:26 ` Frederic Weisbecker
2009-05-11 9:32 ` Christoph Hellwig
2009-05-11 10:54 ` Ingo Molnar
2009-05-11 15:29 ` Frank Ch. Eigler
2009-05-09 1:16 ` [PATCH -tip v5 7/7] tracing: add arguments support on " Masami Hiramatsu
2009-05-11 14:35 ` Steven Rostedt
2009-05-09 4:43 ` [PATCH -tip v5 0/7] tracing: kprobe-based event tracer and x86 instruction decoder Ingo Molnar
2009-05-11 15:44 ` Masami Hiramatsu
2009-05-11 14:56 ` Steven Rostedt
2009-05-11 20:04 ` Masami Hiramatsu
2009-05-11 21:47 ` Ingo Molnar
2009-05-12 22:01 ` Masami Hiramatsu
2009-05-13 13:22 ` Ingo Molnar
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