linux-kernel - Re: [PATCH] tracing/eprobe: Update cond flag before enabling trigger

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Date:   Wed, 23 Nov 2022 11:33:04 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
Cc:     Rafael Mendonca <rafaelmendsr@...il.com>,
        "Tzvetomir Stoyanov (VMware)" <tz.stoyanov@...il.com>,
        linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
        Tom Zanussi <zanussi@...nel.org>
Subject: Re: [PATCH] tracing/eprobe: Update cond flag before enabling
 trigger

On Thu, 24 Nov 2022 01:01:52 +0900
Masami Hiramatsu (Google) <mhiramat@...nel.org> wrote:

> On Fri, 18 Nov 2022 11:19:40 -0500
> Steven Rostedt <rostedt@...dmis.org> wrote:
> 
> > On Fri, 18 Nov 2022 10:34:40 -0300
> > Rafael Mendonca <rafaelmendsr@...il.com> wrote:
> >   
> > > It did not trigger the NULL pointer issue to be more specific. When
> > > creating event probe for all events I was unable to create any event for
> > > the xhci-hcd system:
> > > 
> > > root@...alhost:/sys/kernel/tracing# echo 'e xhci-hcd/xhci_add_endpoint' > dynamic_events 
> > > -bash: echo: write error: Invalid argument
> > > 
> > > Debugging the issue it seems that the problem is in the is_good_name()
> > > check, which returns false for "xhci-hcd". Should we sanitize it by  
> > 
> > Ouch. I didn't realize that.  
> 
> Maybe we need better error message so that user can notice which character
> caused the error. 
> 
> >   
> > > converting '-' into '_'?  
> > 
> > Actually, it's just the system name that's an issue. I tested this patch
> > and it appears to work.  
> 
> Ah, the system name is more flexible than the event name because it has
> TRACE_SYSTEM_VAR.
> 
> Steve, can you send me the below patch?

I already did ;-)

  https://patchwork.kernel.org/project/linux-trace-kernel/patch/20221122122345.160f5077@gandalf.local.home/


> 
> BTW, TRACE_DEFINE_ENUM() and TRACE_DEFINE_SIZEOF() macros are using
> TRACE_SYSTEM instead of TRACE_SYSTEM_VAR. Should those use TRACE_SYSTEM_VAR
> for defining a variable?

Hmm, good question. Probably. But since nothing that has a bad name uses
it, we can fix that whenever (but before a system with a hyphen uses those
macros). Do you want to make the change, or shall I?

-- Steve