On Tue, 3 Sep 2013 18:24:04 -0700
"Paul E. McKenney" <paul...@linux.vnet.ibm.com> wrote:
> On Tue, Sep 03, 2013 at 07:57:05PM -0400, Steven Rostedt wrote:
> > Paul, can I still keep all your acks and reviewed-bys on this?
>
> Yep, but some questions below.
>
> Thanx, Paul
>
> > -- Steve
> >
> > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> > index 310b727..899c8c1 100644
> > --- a/kernel/trace/ftrace.c
> > +++ b/kernel/trace/ftrace.c
> > @@ -1373,7 +1373,7 @@ ftrace_hash_rec_enable(struct ftrace_ops *ops, int
> > filter_hash);
> >
> > static int ftrace_convert_size_to_bits(int size)
> > {
> > - int bits;
> > + int bits = 0;
> >
> > /*
> > * Make the hash size about 1/2 the # found
> > diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
> > index f5a9031..0883069 100644
> > --- a/kernel/trace/trace_functions.c
> > +++ b/kernel/trace/trace_functions.c
> > @@ -561,16 +561,21 @@ static inline int init_func_cmd_traceon(void)
> >
> > #ifdef CONFIG_FTRACE_UNSAFE_RCU_CHECKER
> >
> > +static DEFINE_PER_CPU(int, ftrace_rcu_running);
> > static atomic_t ftrace_unsafe_rcu_disabled;
> >
> > void ftrace_unsafe_rcu_checker_disable(void)
> > {
> > atomic_inc(&ftrace_unsafe_rcu_disabled);
> > + /* Make sure the update is seen immediately */
> > + smp_wmb();
>
> smp_mb__after_atomic_inc()?
Yep.
>
> > }
> >
> > void ftrace_unsafe_rcu_checker_enable(void)
> > {
> > atomic_dec(&ftrace_unsafe_rcu_disabled);
> > + /* Make sure the update is seen immediately */
> > + smp_wmb();
>
> smp_mb__after_atomic_dec()?
Yep.
>
> > }
> >
> > static DEFINE_PER_CPU(unsigned long, ftrace_rcu_func);
> > @@ -588,15 +593,14 @@ static void
> > ftrace_unsafe_callback(unsigned long ip, unsigned long parent_ip,
> > struct ftrace_ops *op, struct pt_regs *pt_regs)
> > {
> > - int bit;
> > -
> > + /* Make sure we see disabled or not first */
> > + smp_rmb();
>
> smp_mb__before_atomic_inc()?
Yep.
I'll update it and restart my tests.
Thanks!
-- Steve
>
> > if (atomic_read(&ftrace_unsafe_rcu_disabled))
> > return;
> >
> > preempt_disable_notrace();
> >
> > - bit = trace_test_and_set_recursion(TRACE_FTRACE_START,
> > TRACE_FTRACE_MAX);
> > - if (bit < 0)
> > + if (this_cpu_read(ftrace_rcu_running))
> > goto out;
> >
> > if (WARN_ONCE(ftrace_rcu_unsafe(ip),
> > @@ -604,13 +608,15 @@ ftrace_unsafe_callback(unsigned long ip, unsigned
> > long parent_ip,
> > (void *)ip))
> > goto out;
> >
> > + this_cpu_write(ftrace_rcu_running, 1);
> > this_cpu_write(ftrace_rcu_func, ip);
> > +
> > /* Should trigger a RCU splat if called from unsafe RCU function */
> > rcu_read_lock();
> > rcu_read_unlock();
> > this_cpu_write(ftrace_rcu_func, 0);
> >
> > - trace_clear_recursion(bit);
> > + this_cpu_write(ftrace_rcu_running, 0);
> > out:
> > preempt_enable_notrace();
> > }
> >
--
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