From: Oleg Nesterov <oleg@redhat.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
Anton Arapov <anton@redhat.com>,
Frederic Weisbecker <fweisbec@gmail.com>,
Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/4] uprobes/tracing: Kill the pointless local_save_flags/preempt_count calls
Date: Tue, 9 Apr 2013 16:58:51 +0200 [thread overview]
Message-ID: <20130409145851.GB22913@redhat.com> (raw)
In-Reply-To: <1365436722.25498.14.camel@gandalf.local.home>
On 04/08, Steven Rostedt wrote:
>
> On Fri, 2013-03-29 at 19:15 +0100, Oleg Nesterov wrote:
> > --- a/kernel/trace/trace_uprobe.c
> > +++ b/kernel/trace/trace_uprobe.c
> > @@ -492,17 +492,13 @@ static int uprobe_trace_func(struct trace_uprobe *tu, struct pt_regs *regs)
> > struct ring_buffer_event *event;
> > struct ring_buffer *buffer;
> > u8 *data;
> > - int size, i, pc;
> > - unsigned long irq_flags;
> > + int size, i;
> > struct ftrace_event_call *call = &tu->call;
> >
> > - local_save_flags(irq_flags);
> > - pc = preempt_count();
>
> How about instead, just change the above two and have:
>
> /* uprobes are never called with preemption disabled */
> pc = 0;
> irq_flags = 0;
>
> and leave the rest the same. This will help in future reviewers of the
> code to not have to look up what that "0, 0" is for, and then wonder if
> it should be that way. gcc should optimize it to be exactly the same as
> this patch.
Hmm, just to remind which arguments trace_current_buffer_*() has?
Personally I disagree. And, for example, ftrace_syscall_enter/exit just
use 0,0 for the same reason.
So please tell me if you really want the dummy variables/arguments, in
this case I'll change this code even if I do not like it.
Oleg.
next prev parent reply other threads:[~2013-04-09 15:02 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-29 18:15 [PATCH 0/4] uprobes/tracing: uretprobes, initial preparations Oleg Nesterov
2013-03-29 18:15 ` [PATCH 1/4] uprobes/tracing: Kill the pointless task_pt_regs() calls Oleg Nesterov
2013-04-02 8:57 ` Anton Arapov
2013-04-04 14:24 ` Srikar Dronamraju
2013-03-29 18:15 ` [PATCH 2/4] uprobes/tracing: Kill the pointless seq_print_ip_sym() call Oleg Nesterov
2013-04-02 8:57 ` Anton Arapov
2013-04-04 14:24 ` Srikar Dronamraju
2013-03-29 18:15 ` [PATCH 3/4] uprobes/tracing: Kill the pointless local_save_flags/preempt_count calls Oleg Nesterov
2013-04-02 8:58 ` Anton Arapov
2013-04-04 14:25 ` Srikar Dronamraju
2013-04-05 3:47 ` Masami Hiramatsu
2013-04-05 15:01 ` Oleg Nesterov
2013-04-08 9:29 ` Masami Hiramatsu
2013-04-10 14:58 ` [PATCH 0/1] uprobes/tracing: Don't pass addr=ip to perf_trace_buf_submit() Oleg Nesterov
2013-04-10 14:58 ` [PATCH 1/1] " Oleg Nesterov
2013-04-11 10:19 ` Masami Hiramatsu
2013-04-13 9:28 ` Srikar Dronamraju
2013-04-11 10:38 ` [PATCH 0/1] " Masami Hiramatsu
2013-04-11 11:59 ` Oleg Nesterov
2013-04-12 18:01 ` Steven Rostedt
2013-04-12 21:19 ` Steven Rostedt
2013-04-13 14:02 ` [PATCH 0/1] uprobes/perf: Avoid perf_trace_buf_prepare/submit if ->perf_events is empty Oleg Nesterov
2013-04-13 14:02 ` [PATCH 1/1] " Oleg Nesterov
2013-04-13 18:22 ` [PATCH 0/1] " Oleg Nesterov
2013-04-08 15:58 ` [PATCH 3/4] uprobes/tracing: Kill the pointless local_save_flags/preempt_count calls Steven Rostedt
2013-04-09 14:58 ` Oleg Nesterov [this message]
2013-04-09 15:12 ` Steven Rostedt
2013-03-29 18:15 ` [PATCH 4/4] uprobes/tracing: generalize struct uprobe_trace_entry_head Oleg Nesterov
2013-04-02 8:59 ` Anton Arapov
2013-04-04 14:25 ` Srikar Dronamraju
2013-04-08 15:55 ` Steven Rostedt
2013-04-09 14:50 ` Oleg Nesterov
2013-04-09 15:07 ` Steven Rostedt
2013-04-09 19:32 ` [PATCH v2 0/7] uprobes/tracing: uretprobes Oleg Nesterov
2013-04-09 19:32 ` [PATCH v2 1/7] uprobes/tracing: Generalize struct uprobe_trace_entry_head Oleg Nesterov
2013-04-09 19:32 ` [PATCH v2 2/7] uprobes/tracing: Introduce uprobe_{trace,perf}_print() helpers Oleg Nesterov
2013-04-09 19:32 ` [PATCH v2 3/7] uprobes/tracing: Introduce is_ret_probe() and uretprobe_dispatcher() Oleg Nesterov
2013-04-09 19:32 ` [PATCH v2 4/7] uprobes/tracing: Make uprobe_{trace,perf}_print() uretprobe-friendly Oleg Nesterov
2013-04-13 9:33 ` Srikar Dronamraju
2013-04-09 19:32 ` [PATCH v2 5/7] uprobes/tracing: Make register_uprobe_event() paths uretprobe-friendly Oleg Nesterov
2013-04-09 19:32 ` [PATCH v2 6/7] uprobes/tracing: Make seq_printf() code uretprobe-friendly Oleg Nesterov
2013-04-09 19:32 ` [PATCH v2 7/7] uprobes/tracing: Change create_trace_uprobe() to support uretprobes Oleg Nesterov
2013-04-01 16:08 ` [PATCH 0/6] uprobes/tracing: uretprobes Oleg Nesterov
2013-04-01 16:08 ` [PATCH 1/6] uprobes/tracing: Introduce uprobe_{trace,perf}_print() helpers Oleg Nesterov
2013-04-07 13:58 ` Srikar Dronamraju
2013-04-01 16:08 ` [PATCH 2/6] uprobes/tracing: Introduce is_ret_probe() and uretprobe_dispatcher() Oleg Nesterov
2013-04-07 14:12 ` Srikar Dronamraju
2013-04-01 16:08 ` [PATCH 3/6] uprobes/tracing: Make uprobe_{trace,perf}_print() uretprobe-friendly Oleg Nesterov
2013-04-07 10:31 ` Srikar Dronamraju
2013-04-09 13:33 ` Oleg Nesterov
2013-04-13 9:31 ` Srikar Dronamraju
2013-04-08 17:08 ` Steven Rostedt
2013-04-01 16:08 ` [PATCH 4/6] uprobes/tracing: Make register_uprobe_event() paths uretprobe-friendly Oleg Nesterov
2013-04-07 14:14 ` Srikar Dronamraju
2013-04-01 16:08 ` [PATCH 5/6] uprobes/tracing: Make seq_printf() code uretprobe-friendly Oleg Nesterov
2013-04-07 14:15 ` Srikar Dronamraju
2013-04-01 16:09 ` [PATCH 6/6] uprobes/tracing: Change create_trace_uprobe() to support uretprobes Oleg Nesterov
2013-04-07 14:17 ` Srikar Dronamraju
2013-04-02 13:25 ` [PATCH 0/6] uprobes/tracing: uretprobes Anton Arapov
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