Messages in this thread | | | Date | Wed, 22 Jul 2020 11:25:25 -0400 | From | Steven Rostedt <> | Subject | Re: [PATCH] dynamic debug: allow printing to trace event |
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On Wed, 22 Jul 2020 15:58:22 +0206 John Ogness <john.ogness@linutronix.de> wrote:
> >> +static void dynamic_printk(unsigned int flags, const char *fmt, ...) > >> +{ > >> + if (flags & _DPRINTK_FLAGS_TRACE) { > >> + va_list args; > >> + > >> + va_start(args, fmt); > >> + /* > >> + * All callers include the KERN_DEBUG prefix to keep the > >> + * vprintk case simple; strip it out for tracing. > >> + */ > >> + dynamic_trace(fmt + strlen(KERN_DEBUG), args); > > Do we really need a separate tracing event for this? Why not just: > > ftrace_vprintk(fmt + strlen(KERN_DEBUG), args);
It must be an event, one that can be enabled or disabled separately from trace_printk().
If you are asking if this could be something like trace_printk(), which ftrace_vprintk() is. The reason for that nasty banner when people use trace_printk() is to keep developers from using it as their personal debugging tool in production.
A trace_printk() can not be discretely disabled. It's either totally on, or totally off. And since it is used for debugging, if there's trace_printk()s all over the kernel, you will have to deal with the noise of everyone else's trace_printk(), making trace_printk() useless.
Thus, NAK on using ftrace_vprintk() here.
-- Steve
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