Messages in this thread | | | Date | Tue, 3 Sep 2013 21:51:52 -0400 | From | Steven Rostedt <> | Subject | Re: [RFC][PATCH 01/18 v2] ftrace: Add hash list to save RCU unsafe functions |
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On Tue, 3 Sep 2013 18:24:04 -0700 "Paul E. McKenney" <paulmck@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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