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Message-ID: <20190712153432.GC235410@google.com>
Date: Fri, 12 Jul 2019 11:34:32 -0400
From: Joel Fernandes <joel@...lfernandes.org>
To: "Paul E. McKenney" <paulmck@...ux.ibm.com>
Cc: linux-kernel@...r.kernel.org,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Ingo Molnar <mingo@...hat.com>,
Jonathan Corbet <corbet@....net>,
Josh Triplett <josh@...htriplett.org>, kvm-ppc@...r.kernel.org,
Lai Jiangshan <jiangshanlai@...il.com>,
linux-doc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Michael Ellerman <mpe@...erman.id.au>,
Paul Mackerras <paulus@...abs.org>, rcu@...r.kernel.org,
Steven Rostedt <rostedt@...dmis.org>, byungchul.park@....com,
kernel-team@...roid.com
Subject: Re: [PATCH] treewide: Rename rcu_dereference_raw_notrace to _check
On Fri, Jul 12, 2019 at 08:01:07AM -0700, Paul E. McKenney wrote:
> On Thu, Jul 11, 2019 at 04:45:41PM -0400, Joel Fernandes (Google) wrote:
> > The rcu_dereference_raw_notrace() API name is confusing.
> > It is equivalent to rcu_dereference_raw() except that it also does
> > sparse pointer checking.
> >
> > There are only a few users of rcu_dereference_raw_notrace(). This
> > patches renames all of them to be rcu_dereference_raw_check with the
> > "check" indicating sparse checking.
> >
> > Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>
>
> I queued this, but reworked the commit log and fixed a couple of
> irritating checkpatch issues that were in the original code.
> Does this work for you?
Thanks, yes it looks good to me.
thanks,
- Joel
>
> Thanx, Paul
>
> ------------------------------------------------------------------------
>
> commit bd5c0fea6016c90cf7a9eb0435cd0c373dfdac2f
> Author: Joel Fernandes (Google) <joel@...lfernandes.org>
> Date: Thu Jul 11 16:45:41 2019 -0400
>
> treewide: Rename rcu_dereference_raw_notrace() to _check()
>
> The rcu_dereference_raw_notrace() API name is confusing. It is equivalent
> to rcu_dereference_raw() except that it also does sparse pointer checking.
>
> There are only a few users of rcu_dereference_raw_notrace(). This patches
> renames all of them to be rcu_dereference_raw_check() with the "_check()"
> indicating sparse checking.
>
> Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>
> [ paulmck: Fix checkpatch warnings about parentheses. ]
> Signed-off-by: Paul E. McKenney <paulmck@...ux.ibm.com>
>
> diff --git a/Documentation/RCU/Design/Requirements/Requirements.html b/Documentation/RCU/Design/Requirements/Requirements.html
> index f04c467e55c5..467251f7fef6 100644
> --- a/Documentation/RCU/Design/Requirements/Requirements.html
> +++ b/Documentation/RCU/Design/Requirements/Requirements.html
> @@ -2514,7 +2514,7 @@ disabled across the entire RCU read-side critical section.
> <p>
> It is possible to use tracing on RCU code, but tracing itself
> uses RCU.
> -For this reason, <tt>rcu_dereference_raw_notrace()</tt>
> +For this reason, <tt>rcu_dereference_raw_check()</tt>
> is provided for use by tracing, which avoids the destructive
> recursion that could otherwise ensue.
> This API is also used by virtualization in some architectures,
> diff --git a/arch/powerpc/include/asm/kvm_book3s_64.h b/arch/powerpc/include/asm/kvm_book3s_64.h
> index 21b1ed5df888..53388a311967 100644
> --- a/arch/powerpc/include/asm/kvm_book3s_64.h
> +++ b/arch/powerpc/include/asm/kvm_book3s_64.h
> @@ -546,7 +546,7 @@ static inline void note_hpte_modification(struct kvm *kvm,
> */
> static inline struct kvm_memslots *kvm_memslots_raw(struct kvm *kvm)
> {
> - return rcu_dereference_raw_notrace(kvm->memslots[0]);
> + return rcu_dereference_raw_check(kvm->memslots[0]);
> }
>
> extern void kvmppc_mmu_debugfs_init(struct kvm *kvm);
> diff --git a/include/linux/rculist.h b/include/linux/rculist.h
> index e91ec9ddcd30..932296144131 100644
> --- a/include/linux/rculist.h
> +++ b/include/linux/rculist.h
> @@ -622,7 +622,7 @@ static inline void hlist_add_behind_rcu(struct hlist_node *n,
> * as long as the traversal is guarded by rcu_read_lock().
> */
> #define hlist_for_each_entry_rcu(pos, head, member) \
> - for (pos = hlist_entry_safe (rcu_dereference_raw(hlist_first_rcu(head)),\
> + for (pos = hlist_entry_safe(rcu_dereference_raw(hlist_first_rcu(head)),\
> typeof(*(pos)), member); \
> pos; \
> pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu(\
> @@ -642,10 +642,10 @@ static inline void hlist_add_behind_rcu(struct hlist_node *n,
> * not do any RCU debugging or tracing.
> */
> #define hlist_for_each_entry_rcu_notrace(pos, head, member) \
> - for (pos = hlist_entry_safe (rcu_dereference_raw_notrace(hlist_first_rcu(head)),\
> + for (pos = hlist_entry_safe(rcu_dereference_raw_check(hlist_first_rcu(head)),\
> typeof(*(pos)), member); \
> pos; \
> - pos = hlist_entry_safe(rcu_dereference_raw_notrace(hlist_next_rcu(\
> + pos = hlist_entry_safe(rcu_dereference_raw_check(hlist_next_rcu(\
> &(pos)->member)), typeof(*(pos)), member))
>
> /**
> diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
> index 0c9b92799abc..e5161e377ad4 100644
> --- a/include/linux/rcupdate.h
> +++ b/include/linux/rcupdate.h
> @@ -478,7 +478,7 @@ do { \
> * The no-tracing version of rcu_dereference_raw() must not call
> * rcu_read_lock_held().
> */
> -#define rcu_dereference_raw_notrace(p) __rcu_dereference_check((p), 1, __rcu)
> +#define rcu_dereference_raw_check(p) __rcu_dereference_check((p), 1, __rcu)
>
> /**
> * rcu_dereference_protected() - fetch RCU pointer when updates prevented
> diff --git a/kernel/trace/ftrace_internal.h b/kernel/trace/ftrace_internal.h
> index 0515a2096f90..0456e0a3dab1 100644
> --- a/kernel/trace/ftrace_internal.h
> +++ b/kernel/trace/ftrace_internal.h
> @@ -6,22 +6,22 @@
>
> /*
> * Traverse the ftrace_global_list, invoking all entries. The reason that we
> - * can use rcu_dereference_raw_notrace() is that elements removed from this list
> + * can use rcu_dereference_raw_check() is that elements removed from this list
> * are simply leaked, so there is no need to interact with a grace-period
> - * mechanism. The rcu_dereference_raw_notrace() calls are needed to handle
> + * mechanism. The rcu_dereference_raw_check() calls are needed to handle
> * concurrent insertions into the ftrace_global_list.
> *
> * Silly Alpha and silly pointer-speculation compiler optimizations!
> */
> #define do_for_each_ftrace_op(op, list) \
> - op = rcu_dereference_raw_notrace(list); \
> + op = rcu_dereference_raw_check(list); \
> do
>
> /*
> * Optimized for just a single item in the list (as that is the normal case).
> */
> #define while_for_each_ftrace_op(op) \
> - while (likely(op = rcu_dereference_raw_notrace((op)->next)) && \
> + while (likely(op = rcu_dereference_raw_check((op)->next)) && \
> unlikely((op) != &ftrace_list_end))
>
> extern struct ftrace_ops __rcu *ftrace_ops_list;
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 2c92b3d9ea30..1d69110d9e5b 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -2642,10 +2642,10 @@ static void ftrace_exports(struct ring_buffer_event *event)
>
> preempt_disable_notrace();
>
> - export = rcu_dereference_raw_notrace(ftrace_exports_list);
> + export = rcu_dereference_raw_check(ftrace_exports_list);
> while (export) {
> trace_process_export(export, event);
> - export = rcu_dereference_raw_notrace(export->next);
> + export = rcu_dereference_raw_check(export->next);
> }
>
> preempt_enable_notrace();
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