Messages in this thread | | | Date | Mon, 4 May 2015 22:55:44 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH] rcu: declare rcu_data variables in the section they are defined in |
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On Tue, May 05, 2015 at 08:40:55AM +0800, Nicolas Iooss wrote: > On 05/05/2015 04:33 AM, Paul E. McKenney wrote: > > On Sun, May 03, 2015 at 12:27:02PM -0700, Josh Triplett wrote: > >> On Sun, May 03, 2015 at 05:57:53PM +0800, Nicolas Iooss wrote: > >>> Commit 11bbb235c26f ("rcu: Use DEFINE_PER_CPU_SHARED_ALIGNED for > >>> rcu_data") replaced DEFINE_PER_CPU by DEFINE_PER_CPU_SHARED_ALIGNED in > >>> the definition of rcu_sched and rcu_bh without updating > >>> kernel/rcu/tree.h. > >>> > >>> This makes clang report a section mismatch (-Wsection warning) when > >>> building LLVMLinux because the variables are declared in .data..percpu > >>> but defined in .data..percpu..shared_aligned. > >>> > >>> Signed-off-by: Nicolas Iooss <nicolas.iooss_linux@m4x.org> > >> > >> Good catch. > >> Reviewed-by: Josh Triplett <josh@joshtriplett.org> > > > > Agreed, good catch! But don't we also need to worry about > > rcu_preempt_data? > > Yes, I missed it because I didn't know that allyesconfig/allmodconfig > does not select CONFIG_PREEMPT (it selects CONFIG_PREEMPT_NONE instead). > > > Also, given that tree_trace.c now uses iterators > > rather than direct access via the per-CPU variables, wouldn't the > > following be more appropriate? (-Very- lightly tested.) > > This doesn't work with CONFIG_TREE_RCU_TRACE, because > kernel/rcu/tree_trace.c uses rcu_preempt_state (in v4.1-rc2). I've > successfully built an allmodconfig+CONFIG_PREEMPT kernel for x86_64 with > the following patch (I have not tested the result). > > Anyway, thanks for your quick replies.
Good point, and your patch does look better.
If you resend with proper changelog and Signed-off-by, and if Josh is good with the change, I will queue it.
Thanx, Paul
> Nicolas > > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -91,7 +91,7 @@ static const char *tp_##sname##_varname __used > __tracepoint_string = sname##_var > > #define RCU_STATE_INITIALIZER(sname, sabbr, cr) \ > DEFINE_RCU_TPS(sname) \ > -DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_data, sname##_data); \ > +static DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_data, sname##_data); \ > struct rcu_state sname##_state = { \ > .level = { &sname##_state.node[0] }, \ > .rda = &sname##_data, \ > --- a/kernel/rcu/tree.h > +++ b/kernel/rcu/tree.h > @@ -519,14 +519,11 @@ extern struct list_head rcu_struct_flavors; > * RCU implementation internal declarations: > */ > extern struct rcu_state rcu_sched_state; > -DECLARE_PER_CPU(struct rcu_data, rcu_sched_data); > > extern struct rcu_state rcu_bh_state; > -DECLARE_PER_CPU(struct rcu_data, rcu_bh_data); > > #ifdef CONFIG_PREEMPT_RCU > extern struct rcu_state rcu_preempt_state; > -DECLARE_PER_CPU(struct rcu_data, rcu_preempt_data); > #endif /* #ifdef CONFIG_PREEMPT_RCU */ > > #ifdef CONFIG_RCU_BOOST >
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