On Tue, Sep 03, 2013 at 09:11:27PM -0400, Steven Rostedt wrote: > From f8f5d278e272c42349b3cd32485faf426d0c459e Mon Sep 17 00:00:00 2001 > From: "Steven Rostedt (Red Hat)" <[email protected]> > Date: Tue, 3 Sep 2013 20:47:59 -0400 > Subject: [PATCH] ftrace: Print a message when the rcu checker is disabled > > Let the user know that the RCU safety checker for function tracing > has been disabled. The checker only runs when the user specifically > configures it in the kernel, and this is done to search for locations > in the kernel that may be unsafe for a function trace callback to > use rcu_read_lock()s. But if things like function graph tracing is > started, which can live lock the machine when the checker is running, > it is disabled. It would be nice if the kernel let the user know that > the checker is disabled, and when it is re-enabled again. > > As the checker only gets disabled and re-enabled by user actions > (starting and stoping the function graph tracer or the irqsoff tracer) > it is fine to have a printk display that it is disabled or not. > > Suggested-by: Paul E. McKenney <[email protected]> > Signed-off-by: Steven Rostedt <[email protected]>
Reviewed-by: Paul E. McKenney <[email protected]> > --- > kernel/trace/trace_functions.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c > index 0883069..dd59827 100644 > --- a/kernel/trace/trace_functions.c > +++ b/kernel/trace/trace_functions.c > @@ -569,6 +569,8 @@ void ftrace_unsafe_rcu_checker_disable(void) > atomic_inc(&ftrace_unsafe_rcu_disabled); > /* Make sure the update is seen immediately */ > smp_wmb(); > + pr_info("Disabled FTRACE RCU checker (%pS)\n", > + __builtin_return_address(0)); > } > > void ftrace_unsafe_rcu_checker_enable(void) > @@ -576,6 +578,8 @@ void ftrace_unsafe_rcu_checker_enable(void) > atomic_dec(&ftrace_unsafe_rcu_disabled); > /* Make sure the update is seen immediately */ > smp_wmb(); > + pr_info("Enabled FTRACE RCU checker (%pS)\n", > + __builtin_return_address(0)); > } > > static DEFINE_PER_CPU(unsigned long, ftrace_rcu_func); > -- > 1.8.1.4 > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
