Quoting Paul [1]:
"Given that a quick (and perhaps error-prone) search of the uses
of rcu_assign_pointer() in v5.1 didn't find a single use of the
return value, let's please instead change the documentation and
implementation to eliminate the return value."
[1] https://lkml.kernel.org/r/[email protected]
Signed-off-by: Andrea Parri <[email protected]>
Cc: "Paul E. McKenney" <[email protected]>
Cc: Josh Triplett <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Cc: Lai Jiangshan <[email protected]>
Cc: Joel Fernandes <[email protected]>
Cc: [email protected]
Cc: Peter Zijlstra <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Sasha Levin <[email protected]>
---
Matthew, Sasha:
The patch is based on -rcu/dev; I took the liberty of applying the
same change to your #defines in:
tools/testing/radix-tree/linux/rcupdate.h
tools/include/linux/rcu.h
but I admit that I'm not familiar with their uses: please shout if
you have any objections with it.
---
Documentation/RCU/whatisRCU.txt | 8 ++++----
include/linux/rcupdate.h | 5 ++---
tools/include/linux/rcu.h | 11 +++++++++--
tools/testing/radix-tree/linux/rcupdate.h | 5 ++++-
4 files changed, 19 insertions(+), 10 deletions(-)
diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt
index 981651a8b65d2..f99a87b9a88fa 100644
--- a/Documentation/RCU/whatisRCU.txt
+++ b/Documentation/RCU/whatisRCU.txt
@@ -212,7 +212,7 @@ synchronize_rcu()
rcu_assign_pointer()
- typeof(p) rcu_assign_pointer(p, typeof(p) v);
+ rcu_assign_pointer(p, typeof(p) v);
Yes, rcu_assign_pointer() -is- implemented as a macro, though it
would be cool to be able to declare a function in this manner.
@@ -220,9 +220,9 @@ rcu_assign_pointer()
The updater uses this function to assign a new value to an
RCU-protected pointer, in order to safely communicate the change
- in value from the updater to the reader. This function returns
- the new value, and also executes any memory-barrier instructions
- required for a given CPU architecture.
+ in value from the updater to the reader. This macro does not
+ evaluate to an rvalue, but it does execute any memory-barrier
+ instructions required for a given CPU architecture.
Perhaps just as important, it serves to document (1) which
pointers are protected by RCU and (2) the point at which a
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 915460ec08722..a5f61a08e65fc 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -367,7 +367,7 @@ static inline void rcu_preempt_sleep_check(void) { }
* other macros that it invokes.
*/
#define rcu_assign_pointer(p, v) \
-({ \
+do { \
uintptr_t _r_a_p__v = (uintptr_t)(v); \
rcu_check_sparse(p, __rcu); \
\
@@ -375,8 +375,7 @@ static inline void rcu_preempt_sleep_check(void) { }
WRITE_ONCE((p), (typeof(p))(_r_a_p__v)); \
else \
smp_store_release(&p, RCU_INITIALIZER((typeof(p))_r_a_p__v)); \
- _r_a_p__v; \
-})
+} while (0)
/**
* rcu_swap_protected() - swap an RCU and a regular pointer
diff --git a/tools/include/linux/rcu.h b/tools/include/linux/rcu.h
index 7d02527e5bcea..01a435ee48cd6 100644
--- a/tools/include/linux/rcu.h
+++ b/tools/include/linux/rcu.h
@@ -19,7 +19,14 @@ static inline bool rcu_is_watching(void)
return false;
}
-#define rcu_assign_pointer(p, v) ((p) = (v))
-#define RCU_INIT_POINTER(p, v) p=(v)
+#define rcu_assign_pointer(p, v) \
+do { \
+ (p) = (v); \
+} while (0)
+
+#define RCU_INIT_POINTER(p, v) \
+do { \
+ (p) = (v); \
+} while (0)
#endif
diff --git a/tools/testing/radix-tree/linux/rcupdate.h b/tools/testing/radix-tree/linux/rcupdate.h
index fd280b070fdb1..48212f3a758e6 100644
--- a/tools/testing/radix-tree/linux/rcupdate.h
+++ b/tools/testing/radix-tree/linux/rcupdate.h
@@ -7,6 +7,9 @@
#define rcu_dereference_raw(p) rcu_dereference(p)
#define rcu_dereference_protected(p, cond) rcu_dereference(p)
#define rcu_dereference_check(p, cond) rcu_dereference(p)
-#define RCU_INIT_POINTER(p, v) (p) = (v)
+#define RCU_INIT_POINTER(p, v) \
+do { \
+ (p) = (v); \
+} while (0)
#endif
--
2.7.4
On Fri, May 24, 2019 at 12:36:37PM +0200, Andrea Parri wrote:
> Quoting Paul [1]:
>
> "Given that a quick (and perhaps error-prone) search of the uses
> of rcu_assign_pointer() in v5.1 didn't find a single use of the
> return value, let's please instead change the documentation and
> implementation to eliminate the return value."
>
> [1] https://lkml.kernel.org/r/[email protected]
Thank you! A few comments below.
Thanx, Paul
> Signed-off-by: Andrea Parri <[email protected]>
> Cc: "Paul E. McKenney" <[email protected]>
> Cc: Josh Triplett <[email protected]>
> Cc: Steven Rostedt <[email protected]>
> Cc: Mathieu Desnoyers <[email protected]>
> Cc: Lai Jiangshan <[email protected]>
> Cc: Joel Fernandes <[email protected]>
> Cc: [email protected]
> Cc: Peter Zijlstra <[email protected]>
> Cc: Will Deacon <[email protected]>
> Cc: Mark Rutland <[email protected]>
> Cc: Matthew Wilcox <[email protected]>
> Cc: Sasha Levin <[email protected]>
> ---
> Matthew, Sasha:
>
> The patch is based on -rcu/dev; I took the liberty of applying the
> same change to your #defines in:
>
> tools/testing/radix-tree/linux/rcupdate.h
> tools/include/linux/rcu.h
>
> but I admit that I'm not familiar with their uses: please shout if
> you have any objections with it.
> ---
> Documentation/RCU/whatisRCU.txt | 8 ++++----
> include/linux/rcupdate.h | 5 ++---
> tools/include/linux/rcu.h | 11 +++++++++--
> tools/testing/radix-tree/linux/rcupdate.h | 5 ++++-
> 4 files changed, 19 insertions(+), 10 deletions(-)
>
> diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt
> index 981651a8b65d2..f99a87b9a88fa 100644
> --- a/Documentation/RCU/whatisRCU.txt
> +++ b/Documentation/RCU/whatisRCU.txt
> @@ -212,7 +212,7 @@ synchronize_rcu()
>
> rcu_assign_pointer()
>
> - typeof(p) rcu_assign_pointer(p, typeof(p) v);
> + rcu_assign_pointer(p, typeof(p) v);
Please add the "void", similar to synchronize_rcu() above.
> Yes, rcu_assign_pointer() -is- implemented as a macro, though it
> would be cool to be able to declare a function in this manner.
> @@ -220,9 +220,9 @@ rcu_assign_pointer()
>
> The updater uses this function to assign a new value to an
> RCU-protected pointer, in order to safely communicate the change
> - in value from the updater to the reader. This function returns
> - the new value, and also executes any memory-barrier instructions
> - required for a given CPU architecture.
> + in value from the updater to the reader. This macro does not
> + evaluate to an rvalue, but it does execute any memory-barrier
> + instructions required for a given CPU architecture.
>
> Perhaps just as important, it serves to document (1) which
> pointers are protected by RCU and (2) the point at which a
> diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
> index 915460ec08722..a5f61a08e65fc 100644
> --- a/include/linux/rcupdate.h
> +++ b/include/linux/rcupdate.h
> @@ -367,7 +367,7 @@ static inline void rcu_preempt_sleep_check(void) { }
> * other macros that it invokes.
> */
> #define rcu_assign_pointer(p, v) \
> -({ \
> +do { \
> uintptr_t _r_a_p__v = (uintptr_t)(v); \
> rcu_check_sparse(p, __rcu); \
> \
> @@ -375,8 +375,7 @@ static inline void rcu_preempt_sleep_check(void) { }
> WRITE_ONCE((p), (typeof(p))(_r_a_p__v)); \
> else \
> smp_store_release(&p, RCU_INITIALIZER((typeof(p))_r_a_p__v)); \
> - _r_a_p__v; \
> -})
> +} while (0)
>
> /**
> * rcu_swap_protected() - swap an RCU and a regular pointer
> diff --git a/tools/include/linux/rcu.h b/tools/include/linux/rcu.h
> index 7d02527e5bcea..01a435ee48cd6 100644
> --- a/tools/include/linux/rcu.h
> +++ b/tools/include/linux/rcu.h
> @@ -19,7 +19,14 @@ static inline bool rcu_is_watching(void)
> return false;
> }
>
> -#define rcu_assign_pointer(p, v) ((p) = (v))
> -#define RCU_INIT_POINTER(p, v) p=(v)
> +#define rcu_assign_pointer(p, v) \
> +do { \
> + (p) = (v); \
> +} while (0)
> +
> +#define RCU_INIT_POINTER(p, v) \
> +do { \
> + (p) = (v); \
> +} while (0)
These two each fit nicely on one line:
#define rcu_assign_pointer(p, v) do { (p) = (v); } while (0)
#define RCU_INIT_POINTER(p, v) do { (p) = (v); } while (0)
>
> #endif
> diff --git a/tools/testing/radix-tree/linux/rcupdate.h b/tools/testing/radix-tree/linux/rcupdate.h
> index fd280b070fdb1..48212f3a758e6 100644
> --- a/tools/testing/radix-tree/linux/rcupdate.h
> +++ b/tools/testing/radix-tree/linux/rcupdate.h
> @@ -7,6 +7,9 @@
> #define rcu_dereference_raw(p) rcu_dereference(p)
> #define rcu_dereference_protected(p, cond) rcu_dereference(p)
> #define rcu_dereference_check(p, cond) rcu_dereference(p)
> -#define RCU_INIT_POINTER(p, v) (p) = (v)
> +#define RCU_INIT_POINTER(p, v) \
> +do { \
> + (p) = (v); \
> +} while (0)
As does this one.
> #endif
> --
> 2.7.4
>
On Fri, May 24, 2019 at 12:36:37PM +0200, Andrea Parri wrote:
> Quoting Paul [1]:
>
> "Given that a quick (and perhaps error-prone) search of the uses
> of rcu_assign_pointer() in v5.1 didn't find a single use of the
> return value, let's please instead change the documentation and
> implementation to eliminate the return value."
>
> [1] https://lkml.kernel.org/r/[email protected]
>
> Signed-off-by: Andrea Parri <[email protected]>
> Cc: "Paul E. McKenney" <[email protected]>
> Cc: Josh Triplett <[email protected]>
> Cc: Steven Rostedt <[email protected]>
> Cc: Mathieu Desnoyers <[email protected]>
> Cc: Lai Jiangshan <[email protected]>
> Cc: Joel Fernandes <[email protected]>
> Cc: [email protected]
> Cc: Peter Zijlstra <[email protected]>
> Cc: Will Deacon <[email protected]>
> Cc: Mark Rutland <[email protected]>
> Cc: Matthew Wilcox <[email protected]>
> Cc: Sasha Levin <[email protected]>
> ---
> Matthew, Sasha:
>
> The patch is based on -rcu/dev; I took the liberty of applying the
> same change to your #defines in:
>
> tools/testing/radix-tree/linux/rcupdate.h
> tools/include/linux/rcu.h
>
> but I admit that I'm not familiar with their uses: please shout if
> you have any objections with it.
> ---
> Documentation/RCU/whatisRCU.txt | 8 ++++----
> include/linux/rcupdate.h | 5 ++---
> tools/include/linux/rcu.h | 11 +++++++++--
> tools/testing/radix-tree/linux/rcupdate.h | 5 ++++-
> 4 files changed, 19 insertions(+), 10 deletions(-)
>
> diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt
> index 981651a8b65d2..f99a87b9a88fa 100644
> --- a/Documentation/RCU/whatisRCU.txt
> +++ b/Documentation/RCU/whatisRCU.txt
> @@ -212,7 +212,7 @@ synchronize_rcu()
>
> rcu_assign_pointer()
>
> - typeof(p) rcu_assign_pointer(p, typeof(p) v);
> + rcu_assign_pointer(p, typeof(p) v);
>
> Yes, rcu_assign_pointer() -is- implemented as a macro, though it
> would be cool to be able to declare a function in this manner.
> @@ -220,9 +220,9 @@ rcu_assign_pointer()
>
> The updater uses this function to assign a new value to an
> RCU-protected pointer, in order to safely communicate the change
> - in value from the updater to the reader. This function returns
> - the new value, and also executes any memory-barrier instructions
> - required for a given CPU architecture.
> + in value from the updater to the reader. This macro does not
> + evaluate to an rvalue, but it does execute any memory-barrier
> + instructions required for a given CPU architecture.
>
> Perhaps just as important, it serves to document (1) which
> pointers are protected by RCU and (2) the point at which a
> diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
> index 915460ec08722..a5f61a08e65fc 100644
> --- a/include/linux/rcupdate.h
> +++ b/include/linux/rcupdate.h
> @@ -367,7 +367,7 @@ static inline void rcu_preempt_sleep_check(void) { }
> * other macros that it invokes.
> */
> #define rcu_assign_pointer(p, v) \
> -({ \
> +do { \
> uintptr_t _r_a_p__v = (uintptr_t)(v); \
> rcu_check_sparse(p, __rcu); \
> \
> @@ -375,8 +375,7 @@ static inline void rcu_preempt_sleep_check(void) { }
> WRITE_ONCE((p), (typeof(p))(_r_a_p__v)); \
> else \
> smp_store_release(&p, RCU_INITIALIZER((typeof(p))_r_a_p__v)); \
> - _r_a_p__v; \
> -})
> +} while (0)
>
> /**
> * rcu_swap_protected() - swap an RCU and a regular pointer
> diff --git a/tools/include/linux/rcu.h b/tools/include/linux/rcu.h
> index 7d02527e5bcea..01a435ee48cd6 100644
> --- a/tools/include/linux/rcu.h
> +++ b/tools/include/linux/rcu.h
> @@ -19,7 +19,14 @@ static inline bool rcu_is_watching(void)
> return false;
> }
>
> -#define rcu_assign_pointer(p, v) ((p) = (v))
> -#define RCU_INIT_POINTER(p, v) p=(v)
> +#define rcu_assign_pointer(p, v) \
> +do { \
> + (p) = (v); \
> +} while (0)
> +
> +#define RCU_INIT_POINTER(p, v) \
> +do { \
> + (p) = (v); \
> +} while (0)
>
> #endif
> diff --git a/tools/testing/radix-tree/linux/rcupdate.h b/tools/testing/radix-tree/linux/rcupdate.h
> index fd280b070fdb1..48212f3a758e6 100644
> --- a/tools/testing/radix-tree/linux/rcupdate.h
> +++ b/tools/testing/radix-tree/linux/rcupdate.h
> @@ -7,6 +7,9 @@
> #define rcu_dereference_raw(p) rcu_dereference(p)
> #define rcu_dereference_protected(p, cond) rcu_dereference(p)
> #define rcu_dereference_check(p, cond) rcu_dereference(p)
> -#define RCU_INIT_POINTER(p, v) (p) = (v)
> +#define RCU_INIT_POINTER(p, v) \
> +do { \
> + (p) = (v); \
> +} while (0)
>
> #endif
> --
> 2.7.4
>
Other than Paul's nits, LGTM. Thanks.
On Fri, May 24, 2019 at 06:29:11AM -0700, Paul E. McKenney wrote:
> On Fri, May 24, 2019 at 12:36:37PM +0200, Andrea Parri wrote:
> > Quoting Paul [1]:
> >
> > "Given that a quick (and perhaps error-prone) search of the uses
> > of rcu_assign_pointer() in v5.1 didn't find a single use of the
> > return value, let's please instead change the documentation and
> > implementation to eliminate the return value."
> >
> > [1] https://lkml.kernel.org/r/[email protected]
>
> Thank you! A few comments below.
Thank you for the suggestions, Paul.
>
> Thanx, Paul
>
> > Signed-off-by: Andrea Parri <[email protected]>
> > Cc: "Paul E. McKenney" <[email protected]>
> > Cc: Josh Triplett <[email protected]>
> > Cc: Steven Rostedt <[email protected]>
> > Cc: Mathieu Desnoyers <[email protected]>
> > Cc: Lai Jiangshan <[email protected]>
> > Cc: Joel Fernandes <[email protected]>
> > Cc: [email protected]
> > Cc: Peter Zijlstra <[email protected]>
> > Cc: Will Deacon <[email protected]>
> > Cc: Mark Rutland <[email protected]>
> > Cc: Matthew Wilcox <[email protected]>
> > Cc: Sasha Levin <[email protected]>
> > ---
> > Matthew, Sasha:
> >
> > The patch is based on -rcu/dev; I took the liberty of applying the
> > same change to your #defines in:
> >
> > tools/testing/radix-tree/linux/rcupdate.h
> > tools/include/linux/rcu.h
> >
> > but I admit that I'm not familiar with their uses: please shout if
> > you have any objections with it.
> > ---
> > Documentation/RCU/whatisRCU.txt | 8 ++++----
> > include/linux/rcupdate.h | 5 ++---
> > tools/include/linux/rcu.h | 11 +++++++++--
> > tools/testing/radix-tree/linux/rcupdate.h | 5 ++++-
> > 4 files changed, 19 insertions(+), 10 deletions(-)
> >
> > diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt
> > index 981651a8b65d2..f99a87b9a88fa 100644
> > --- a/Documentation/RCU/whatisRCU.txt
> > +++ b/Documentation/RCU/whatisRCU.txt
> > @@ -212,7 +212,7 @@ synchronize_rcu()
> >
> > rcu_assign_pointer()
> >
> > - typeof(p) rcu_assign_pointer(p, typeof(p) v);
> > + rcu_assign_pointer(p, typeof(p) v);
>
> Please add the "void", similar to synchronize_rcu() above.
Sure, will do in v2.
>
> > Yes, rcu_assign_pointer() -is- implemented as a macro, though it
> > would be cool to be able to declare a function in this manner.
> > @@ -220,9 +220,9 @@ rcu_assign_pointer()
> >
> > The updater uses this function to assign a new value to an
> > RCU-protected pointer, in order to safely communicate the change
> > - in value from the updater to the reader. This function returns
> > - the new value, and also executes any memory-barrier instructions
> > - required for a given CPU architecture.
> > + in value from the updater to the reader. This macro does not
> > + evaluate to an rvalue, but it does execute any memory-barrier
> > + instructions required for a given CPU architecture.
> >
> > Perhaps just as important, it serves to document (1) which
> > pointers are protected by RCU and (2) the point at which a
> > diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
> > index 915460ec08722..a5f61a08e65fc 100644
> > --- a/include/linux/rcupdate.h
> > +++ b/include/linux/rcupdate.h
> > @@ -367,7 +367,7 @@ static inline void rcu_preempt_sleep_check(void) { }
> > * other macros that it invokes.
> > */
> > #define rcu_assign_pointer(p, v) \
> > -({ \
> > +do { \
> > uintptr_t _r_a_p__v = (uintptr_t)(v); \
> > rcu_check_sparse(p, __rcu); \
> > \
> > @@ -375,8 +375,7 @@ static inline void rcu_preempt_sleep_check(void) { }
> > WRITE_ONCE((p), (typeof(p))(_r_a_p__v)); \
> > else \
> > smp_store_release(&p, RCU_INITIALIZER((typeof(p))_r_a_p__v)); \
> > - _r_a_p__v; \
> > -})
> > +} while (0)
> >
> > /**
> > * rcu_swap_protected() - swap an RCU and a regular pointer
> > diff --git a/tools/include/linux/rcu.h b/tools/include/linux/rcu.h
> > index 7d02527e5bcea..01a435ee48cd6 100644
> > --- a/tools/include/linux/rcu.h
> > +++ b/tools/include/linux/rcu.h
> > @@ -19,7 +19,14 @@ static inline bool rcu_is_watching(void)
> > return false;
> > }
> >
> > -#define rcu_assign_pointer(p, v) ((p) = (v))
> > -#define RCU_INIT_POINTER(p, v) p=(v)
> > +#define rcu_assign_pointer(p, v) \
> > +do { \
> > + (p) = (v); \
> > +} while (0)
> > +
> > +#define RCU_INIT_POINTER(p, v) \
> > +do { \
> > + (p) = (v); \
> > +} while (0)
>
> These two each fit nicely on one line:
>
> #define rcu_assign_pointer(p, v) do { (p) = (v); } while (0)
> #define RCU_INIT_POINTER(p, v) do { (p) = (v); } while (0)
Same here.
>
> >
> > #endif
> > diff --git a/tools/testing/radix-tree/linux/rcupdate.h b/tools/testing/radix-tree/linux/rcupdate.h
> > index fd280b070fdb1..48212f3a758e6 100644
> > --- a/tools/testing/radix-tree/linux/rcupdate.h
> > +++ b/tools/testing/radix-tree/linux/rcupdate.h
> > @@ -7,6 +7,9 @@
> > #define rcu_dereference_raw(p) rcu_dereference(p)
> > #define rcu_dereference_protected(p, cond) rcu_dereference(p)
> > #define rcu_dereference_check(p, cond) rcu_dereference(p)
> > -#define RCU_INIT_POINTER(p, v) (p) = (v)
> > +#define RCU_INIT_POINTER(p, v) \
> > +do { \
> > + (p) = (v); \
> > +} while (0)
>
> As does this one.
... And here.
Thanks,
Andrea
On Fri, May 24, 2019 at 12:45:09PM -0400, Joel Fernandes wrote:
> On Fri, May 24, 2019 at 12:36:37PM +0200, Andrea Parri wrote:
> > Quoting Paul [1]:
> >
> > "Given that a quick (and perhaps error-prone) search of the uses
> > of rcu_assign_pointer() in v5.1 didn't find a single use of the
> > return value, let's please instead change the documentation and
> > implementation to eliminate the return value."
> >
> > [1] https://lkml.kernel.org/r/[email protected]
> >
> > Signed-off-by: Andrea Parri <[email protected]>
> > Cc: "Paul E. McKenney" <[email protected]>
> > Cc: Josh Triplett <[email protected]>
> > Cc: Steven Rostedt <[email protected]>
> > Cc: Mathieu Desnoyers <[email protected]>
> > Cc: Lai Jiangshan <[email protected]>
> > Cc: Joel Fernandes <[email protected]>
> > Cc: [email protected]
> > Cc: Peter Zijlstra <[email protected]>
> > Cc: Will Deacon <[email protected]>
> > Cc: Mark Rutland <[email protected]>
> > Cc: Matthew Wilcox <[email protected]>
> > Cc: Sasha Levin <[email protected]>
> > ---
> > Matthew, Sasha:
> >
> > The patch is based on -rcu/dev; I took the liberty of applying the
> > same change to your #defines in:
> >
> > tools/testing/radix-tree/linux/rcupdate.h
> > tools/include/linux/rcu.h
> >
> > but I admit that I'm not familiar with their uses: please shout if
> > you have any objections with it.
> > ---
> > Documentation/RCU/whatisRCU.txt | 8 ++++----
> > include/linux/rcupdate.h | 5 ++---
> > tools/include/linux/rcu.h | 11 +++++++++--
> > tools/testing/radix-tree/linux/rcupdate.h | 5 ++++-
> > 4 files changed, 19 insertions(+), 10 deletions(-)
> >
> > diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt
> > index 981651a8b65d2..f99a87b9a88fa 100644
> > --- a/Documentation/RCU/whatisRCU.txt
> > +++ b/Documentation/RCU/whatisRCU.txt
> > @@ -212,7 +212,7 @@ synchronize_rcu()
> >
> > rcu_assign_pointer()
> >
> > - typeof(p) rcu_assign_pointer(p, typeof(p) v);
> > + rcu_assign_pointer(p, typeof(p) v);
> >
> > Yes, rcu_assign_pointer() -is- implemented as a macro, though it
> > would be cool to be able to declare a function in this manner.
> > @@ -220,9 +220,9 @@ rcu_assign_pointer()
> >
> > The updater uses this function to assign a new value to an
> > RCU-protected pointer, in order to safely communicate the change
> > - in value from the updater to the reader. This function returns
> > - the new value, and also executes any memory-barrier instructions
> > - required for a given CPU architecture.
> > + in value from the updater to the reader. This macro does not
> > + evaluate to an rvalue, but it does execute any memory-barrier
> > + instructions required for a given CPU architecture.
> >
> > Perhaps just as important, it serves to document (1) which
> > pointers are protected by RCU and (2) the point at which a
> > diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
> > index 915460ec08722..a5f61a08e65fc 100644
> > --- a/include/linux/rcupdate.h
> > +++ b/include/linux/rcupdate.h
> > @@ -367,7 +367,7 @@ static inline void rcu_preempt_sleep_check(void) { }
> > * other macros that it invokes.
> > */
> > #define rcu_assign_pointer(p, v) \
> > -({ \
> > +do { \
> > uintptr_t _r_a_p__v = (uintptr_t)(v); \
> > rcu_check_sparse(p, __rcu); \
> > \
> > @@ -375,8 +375,7 @@ static inline void rcu_preempt_sleep_check(void) { }
> > WRITE_ONCE((p), (typeof(p))(_r_a_p__v)); \
> > else \
> > smp_store_release(&p, RCU_INITIALIZER((typeof(p))_r_a_p__v)); \
> > - _r_a_p__v; \
> > -})
> > +} while (0)
> >
> > /**
> > * rcu_swap_protected() - swap an RCU and a regular pointer
> > diff --git a/tools/include/linux/rcu.h b/tools/include/linux/rcu.h
> > index 7d02527e5bcea..01a435ee48cd6 100644
> > --- a/tools/include/linux/rcu.h
> > +++ b/tools/include/linux/rcu.h
> > @@ -19,7 +19,14 @@ static inline bool rcu_is_watching(void)
> > return false;
> > }
> >
> > -#define rcu_assign_pointer(p, v) ((p) = (v))
> > -#define RCU_INIT_POINTER(p, v) p=(v)
> > +#define rcu_assign_pointer(p, v) \
> > +do { \
> > + (p) = (v); \
> > +} while (0)
> > +
> > +#define RCU_INIT_POINTER(p, v) \
> > +do { \
> > + (p) = (v); \
> > +} while (0)
> >
> > #endif
> > diff --git a/tools/testing/radix-tree/linux/rcupdate.h b/tools/testing/radix-tree/linux/rcupdate.h
> > index fd280b070fdb1..48212f3a758e6 100644
> > --- a/tools/testing/radix-tree/linux/rcupdate.h
> > +++ b/tools/testing/radix-tree/linux/rcupdate.h
> > @@ -7,6 +7,9 @@
> > #define rcu_dereference_raw(p) rcu_dereference(p)
> > #define rcu_dereference_protected(p, cond) rcu_dereference(p)
> > #define rcu_dereference_check(p, cond) rcu_dereference(p)
> > -#define RCU_INIT_POINTER(p, v) (p) = (v)
> > +#define RCU_INIT_POINTER(p, v) \
> > +do { \
> > + (p) = (v); \
> > +} while (0)
> >
> > #endif
> > --
> > 2.7.4
> >
>
> Other than Paul's nits, LGTM. Thanks.
Thank you, Joel! Will fix those and resend, most likely next week.
Andrea