* [PATCH tip/core/rcu 2/3] rcu: Optimize rcu_needs_cpu() for RCU_NOCB_CPU_ALL
2014-02-17 21:40 ` [PATCH tip/core/rcu 1/3] rcu: Optimize rcu_is_nocb_cpu() for RCU_NOCB_CPU_ALL Paul E. McKenney
@ 2014-02-17 21:40 ` Paul E. McKenney
2014-02-17 21:53 ` Josh Triplett
2014-02-17 21:40 ` [PATCH tip/core/rcu 3/3] rcu: Optimize RCU_FAST_NO_HZ " Paul E. McKenney
2014-02-17 21:50 ` [PATCH tip/core/rcu 1/3] rcu: Optimize rcu_is_nocb_cpu() " Josh Triplett
2 siblings, 1 reply; 9+ messages in thread
From: Paul E. McKenney @ 2014-02-17 21:40 UTC (permalink / raw)
To: linux-kernel
Cc: mingo, laijs, dipankar, akpm, mathieu.desnoyers, josh, niv, tglx,
peterz, rostedt, dhowells, edumazet, darren, fweisbec, oleg, sbw,
Paul E. McKenney
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
If CONFIG_RCU_NOCB_CPU_ALL=y, then rcu_needs_cpu() will always
return false, however, the current version nevertheless checks
for RCU callbacks. This commit therefore creates a static inline
implementation of rcu_needs_cpu() that unconditionally returns false
when CONFIG_RCU_NOCB_CPU_ALL=y.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
include/linux/rcupdate.h | 9 +++++++++
include/linux/rcutiny.h | 6 ------
include/linux/rcutree.h | 2 ++
kernel/rcu/tree.c | 2 +-
kernel/rcu/tree_plugin.h | 4 ++++
5 files changed, 16 insertions(+), 7 deletions(-)
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 92365b1fede4..da77ef26b4ac 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -1015,6 +1015,15 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)
#define kfree_rcu(ptr, rcu_head) \
__kfree_rcu(&((ptr)->rcu_head), offsetof(typeof(*(ptr)), rcu_head))
+#if defined(CONFIG_TINY_RCU) || defined(CONFIG_RCU_NOCB_CPU_ALL)
+
+static inline int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies)
+{
+ *delta_jiffies = ULONG_MAX;
+ return 0;
+}
+#endif /* #if defined(CONFIG_TINY_RCU) || defined(CONFIG_RCU_NOCB_CPU_ALL) */
+
#ifdef CONFIG_RCU_NOCB_CPU
#ifdef CONFIG_RCU_NOCB_CPU_ALL
static inline bool rcu_is_nocb_cpu(int cpu) { return true; }
diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
index 6f01771b571c..9524903487d0 100644
--- a/include/linux/rcutiny.h
+++ b/include/linux/rcutiny.h
@@ -68,12 +68,6 @@ static inline void kfree_call_rcu(struct rcu_head *head,
call_rcu(head, func);
}
-static inline int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies)
-{
- *delta_jiffies = ULONG_MAX;
- return 0;
-}
-
static inline void rcu_note_context_switch(int cpu)
{
rcu_sched_qs(cpu);
diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
index 72137ee8c603..81198c84e268 100644
--- a/include/linux/rcutree.h
+++ b/include/linux/rcutree.h
@@ -31,7 +31,9 @@
#define __LINUX_RCUTREE_H
void rcu_note_context_switch(int cpu);
+#ifndef CONFIG_RCU_NOCB_CPU_ALL
int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies);
+#endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */
void rcu_cpu_stall_reset(void);
/*
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index b3d116cd072d..c2c8234a0291 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2880,7 +2880,7 @@ static int rcu_pending(int cpu)
* non-NULL, store an indication of whether all callbacks are lazy.
* (If there are no callbacks, all of them are deemed to be lazy.)
*/
-static int rcu_cpu_has_callbacks(int cpu, bool *all_lazy)
+static int __maybe_unused rcu_cpu_has_callbacks(int cpu, bool *all_lazy)
{
bool al = true;
bool hc = false;
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 39a50b918bff..820b06aefbee 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1586,11 +1586,13 @@ static void rcu_prepare_kthreads(int cpu)
* Because we not have RCU_FAST_NO_HZ, just check whether this CPU needs
* any flavor of RCU.
*/
+#ifndef CONFIG_RCU_NOCB_CPU_ALL
int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies)
{
*delta_jiffies = ULONG_MAX;
return rcu_cpu_has_callbacks(cpu, NULL);
}
+#endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */
/*
* Because we do not have RCU_FAST_NO_HZ, don't bother cleaning up
@@ -1696,6 +1698,7 @@ static bool rcu_try_advance_all_cbs(void)
*
* The caller must have disabled interrupts.
*/
+#ifndef CONFIG_RCU_NOCB_CPU_ALL
int rcu_needs_cpu(int cpu, unsigned long *dj)
{
struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
@@ -1726,6 +1729,7 @@ int rcu_needs_cpu(int cpu, unsigned long *dj)
}
return 0;
}
+#endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */
/*
* Prepare a CPU for idle from an RCU perspective. The first major task
--
1.8.1.5
^ permalink raw reply related [flat|nested] 9+ messages in thread* Re: [PATCH tip/core/rcu 2/3] rcu: Optimize rcu_needs_cpu() for RCU_NOCB_CPU_ALL
2014-02-17 21:40 ` [PATCH tip/core/rcu 2/3] rcu: Optimize rcu_needs_cpu() " Paul E. McKenney
@ 2014-02-17 21:53 ` Josh Triplett
0 siblings, 0 replies; 9+ messages in thread
From: Josh Triplett @ 2014-02-17 21:53 UTC (permalink / raw)
To: Paul E. McKenney
Cc: linux-kernel, mingo, laijs, dipankar, akpm, mathieu.desnoyers,
niv, tglx, peterz, rostedt, dhowells, edumazet, darren, fweisbec,
oleg, sbw
On Mon, Feb 17, 2014 at 01:40:26PM -0800, Paul E. McKenney wrote:
> From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
>
> If CONFIG_RCU_NOCB_CPU_ALL=y, then rcu_needs_cpu() will always
> return false, however, the current version nevertheless checks
> for RCU callbacks. This commit therefore creates a static inline
> implementation of rcu_needs_cpu() that unconditionally returns false
> when CONFIG_RCU_NOCB_CPU_ALL=y.
>
> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
> ---
> include/linux/rcupdate.h | 9 +++++++++
> include/linux/rcutiny.h | 6 ------
> include/linux/rcutree.h | 2 ++
> kernel/rcu/tree.c | 2 +-
> kernel/rcu/tree_plugin.h | 4 ++++
> 5 files changed, 16 insertions(+), 7 deletions(-)
>
> diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
> index 92365b1fede4..da77ef26b4ac 100644
> --- a/include/linux/rcupdate.h
> +++ b/include/linux/rcupdate.h
> @@ -1015,6 +1015,15 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)
> #define kfree_rcu(ptr, rcu_head) \
> __kfree_rcu(&((ptr)->rcu_head), offsetof(typeof(*(ptr)), rcu_head))
>
> +#if defined(CONFIG_TINY_RCU) || defined(CONFIG_RCU_NOCB_CPU_ALL)
> +
> +static inline int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies)
> +{
> + *delta_jiffies = ULONG_MAX;
> + return 0;
> +}
> +#endif /* #if defined(CONFIG_TINY_RCU) || defined(CONFIG_RCU_NOCB_CPU_ALL) */
> +
> #ifdef CONFIG_RCU_NOCB_CPU
> #ifdef CONFIG_RCU_NOCB_CPU_ALL
> static inline bool rcu_is_nocb_cpu(int cpu) { return true; }
> diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
> index 6f01771b571c..9524903487d0 100644
> --- a/include/linux/rcutiny.h
> +++ b/include/linux/rcutiny.h
> @@ -68,12 +68,6 @@ static inline void kfree_call_rcu(struct rcu_head *head,
> call_rcu(head, func);
> }
>
> -static inline int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies)
> -{
> - *delta_jiffies = ULONG_MAX;
> - return 0;
> -}
> -
> static inline void rcu_note_context_switch(int cpu)
> {
> rcu_sched_qs(cpu);
> diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
> index 72137ee8c603..81198c84e268 100644
> --- a/include/linux/rcutree.h
> +++ b/include/linux/rcutree.h
> @@ -31,7 +31,9 @@
> #define __LINUX_RCUTREE_H
>
> void rcu_note_context_switch(int cpu);
> +#ifndef CONFIG_RCU_NOCB_CPU_ALL
> int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies);
> +#endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */
> void rcu_cpu_stall_reset(void);
>
> /*
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index b3d116cd072d..c2c8234a0291 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -2880,7 +2880,7 @@ static int rcu_pending(int cpu)
> * non-NULL, store an indication of whether all callbacks are lazy.
> * (If there are no callbacks, all of them are deemed to be lazy.)
> */
> -static int rcu_cpu_has_callbacks(int cpu, bool *all_lazy)
> +static int __maybe_unused rcu_cpu_has_callbacks(int cpu, bool *all_lazy)
> {
> bool al = true;
> bool hc = false;
> diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
> index 39a50b918bff..820b06aefbee 100644
> --- a/kernel/rcu/tree_plugin.h
> +++ b/kernel/rcu/tree_plugin.h
> @@ -1586,11 +1586,13 @@ static void rcu_prepare_kthreads(int cpu)
> * Because we not have RCU_FAST_NO_HZ, just check whether this CPU needs
> * any flavor of RCU.
> */
> +#ifndef CONFIG_RCU_NOCB_CPU_ALL
> int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies)
> {
> *delta_jiffies = ULONG_MAX;
> return rcu_cpu_has_callbacks(cpu, NULL);
> }
> +#endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */
>
> /*
> * Because we do not have RCU_FAST_NO_HZ, don't bother cleaning up
> @@ -1696,6 +1698,7 @@ static bool rcu_try_advance_all_cbs(void)
> *
> * The caller must have disabled interrupts.
> */
> +#ifndef CONFIG_RCU_NOCB_CPU_ALL
> int rcu_needs_cpu(int cpu, unsigned long *dj)
> {
> struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
> @@ -1726,6 +1729,7 @@ int rcu_needs_cpu(int cpu, unsigned long *dj)
> }
> return 0;
> }
> +#endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */
>
> /*
> * Prepare a CPU for idle from an RCU perspective. The first major task
> --
> 1.8.1.5
>
^ permalink raw reply [flat|nested] 9+ messages in thread
* [PATCH tip/core/rcu 3/3] rcu: Optimize RCU_FAST_NO_HZ for RCU_NOCB_CPU_ALL
2014-02-17 21:40 ` [PATCH tip/core/rcu 1/3] rcu: Optimize rcu_is_nocb_cpu() for RCU_NOCB_CPU_ALL Paul E. McKenney
2014-02-17 21:40 ` [PATCH tip/core/rcu 2/3] rcu: Optimize rcu_needs_cpu() " Paul E. McKenney
@ 2014-02-17 21:40 ` Paul E. McKenney
2014-02-17 21:54 ` Josh Triplett
2014-02-17 21:50 ` [PATCH tip/core/rcu 1/3] rcu: Optimize rcu_is_nocb_cpu() " Josh Triplett
2 siblings, 1 reply; 9+ messages in thread
From: Paul E. McKenney @ 2014-02-17 21:40 UTC (permalink / raw)
To: linux-kernel
Cc: mingo, laijs, dipankar, akpm, mathieu.desnoyers, josh, niv, tglx,
peterz, rostedt, dhowells, edumazet, darren, fweisbec, oleg, sbw,
Paul E. McKenney
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
If CONFIG_RCU_NOCB_CPU_ALL=y, then no CPU will ever have RCU callbacks
because these callbacks will instead be handled by the rcuo kthreads.
However, the current version of RCU_FAST_NO_HZ nevertheless checks for RCU
callbacks. This commit therefore creates static inline implementations
of rcu_prepare_for_idle() and rcu_cleanup_after_idle() that are no-ops
when CONFIG_RCU_NOCB_CPU_ALL=y.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
kernel/rcu/tree_plugin.h | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 820b06aefbee..41afc3fbfb6c 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1658,7 +1658,7 @@ extern int tick_nohz_active;
* only if it has been awhile since the last time we did so. Afterwards,
* if there are any callbacks ready for immediate invocation, return true.
*/
-static bool rcu_try_advance_all_cbs(void)
+static bool __maybe_unused rcu_try_advance_all_cbs(void)
{
bool cbs_ready = false;
struct rcu_data *rdp;
@@ -1743,6 +1743,7 @@ int rcu_needs_cpu(int cpu, unsigned long *dj)
*/
static void rcu_prepare_for_idle(int cpu)
{
+#ifndef CONFIG_RCU_NOCB_CPU_ALL
struct rcu_data *rdp;
struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
struct rcu_node *rnp;
@@ -1794,6 +1795,7 @@ static void rcu_prepare_for_idle(int cpu)
rcu_accelerate_cbs(rsp, rnp, rdp);
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
}
+#endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */
}
/*
@@ -1803,11 +1805,12 @@ static void rcu_prepare_for_idle(int cpu)
*/
static void rcu_cleanup_after_idle(int cpu)
{
-
+#ifndef CONFIG_RCU_NOCB_CPU_ALL
if (rcu_is_nocb_cpu(cpu))
return;
if (rcu_try_advance_all_cbs())
invoke_rcu_core();
+#endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */
}
/*
--
1.8.1.5
^ permalink raw reply related [flat|nested] 9+ messages in thread* Re: [PATCH tip/core/rcu 3/3] rcu: Optimize RCU_FAST_NO_HZ for RCU_NOCB_CPU_ALL
2014-02-17 21:40 ` [PATCH tip/core/rcu 3/3] rcu: Optimize RCU_FAST_NO_HZ " Paul E. McKenney
@ 2014-02-17 21:54 ` Josh Triplett
0 siblings, 0 replies; 9+ messages in thread
From: Josh Triplett @ 2014-02-17 21:54 UTC (permalink / raw)
To: Paul E. McKenney
Cc: linux-kernel, mingo, laijs, dipankar, akpm, mathieu.desnoyers,
niv, tglx, peterz, rostedt, dhowells, edumazet, darren, fweisbec,
oleg, sbw
On Mon, Feb 17, 2014 at 01:40:27PM -0800, Paul E. McKenney wrote:
> From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
>
> If CONFIG_RCU_NOCB_CPU_ALL=y, then no CPU will ever have RCU callbacks
> because these callbacks will instead be handled by the rcuo kthreads.
> However, the current version of RCU_FAST_NO_HZ nevertheless checks for RCU
> callbacks. This commit therefore creates static inline implementations
> of rcu_prepare_for_idle() and rcu_cleanup_after_idle() that are no-ops
> when CONFIG_RCU_NOCB_CPU_ALL=y.
"creates static inline implementations" isn't quite accurate; they're
static, and in the header, and the compiler is likely to inline the
no-op versions, but they're not actually marked as inline. The commit
message should just say that it turns the implementations into no-ops.
> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
> ---
> kernel/rcu/tree_plugin.h | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
> index 820b06aefbee..41afc3fbfb6c 100644
> --- a/kernel/rcu/tree_plugin.h
> +++ b/kernel/rcu/tree_plugin.h
> @@ -1658,7 +1658,7 @@ extern int tick_nohz_active;
> * only if it has been awhile since the last time we did so. Afterwards,
> * if there are any callbacks ready for immediate invocation, return true.
> */
> -static bool rcu_try_advance_all_cbs(void)
> +static bool __maybe_unused rcu_try_advance_all_cbs(void)
> {
> bool cbs_ready = false;
> struct rcu_data *rdp;
> @@ -1743,6 +1743,7 @@ int rcu_needs_cpu(int cpu, unsigned long *dj)
> */
> static void rcu_prepare_for_idle(int cpu)
> {
> +#ifndef CONFIG_RCU_NOCB_CPU_ALL
> struct rcu_data *rdp;
> struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
> struct rcu_node *rnp;
> @@ -1794,6 +1795,7 @@ static void rcu_prepare_for_idle(int cpu)
> rcu_accelerate_cbs(rsp, rnp, rdp);
> raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
> }
> +#endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */
> }
>
> /*
> @@ -1803,11 +1805,12 @@ static void rcu_prepare_for_idle(int cpu)
> */
> static void rcu_cleanup_after_idle(int cpu)
> {
> -
> +#ifndef CONFIG_RCU_NOCB_CPU_ALL
> if (rcu_is_nocb_cpu(cpu))
> return;
> if (rcu_try_advance_all_cbs())
> invoke_rcu_core();
> +#endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */
> }
>
> /*
> --
> 1.8.1.5
>
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH tip/core/rcu 1/3] rcu: Optimize rcu_is_nocb_cpu() for RCU_NOCB_CPU_ALL
2014-02-17 21:40 ` [PATCH tip/core/rcu 1/3] rcu: Optimize rcu_is_nocb_cpu() for RCU_NOCB_CPU_ALL Paul E. McKenney
2014-02-17 21:40 ` [PATCH tip/core/rcu 2/3] rcu: Optimize rcu_needs_cpu() " Paul E. McKenney
2014-02-17 21:40 ` [PATCH tip/core/rcu 3/3] rcu: Optimize RCU_FAST_NO_HZ " Paul E. McKenney
@ 2014-02-17 21:50 ` Josh Triplett
2014-02-17 23:33 ` Paul E. McKenney
2 siblings, 1 reply; 9+ messages in thread
From: Josh Triplett @ 2014-02-17 21:50 UTC (permalink / raw)
To: Paul E. McKenney
Cc: linux-kernel, mingo, laijs, dipankar, akpm, mathieu.desnoyers,
niv, tglx, peterz, rostedt, dhowells, edumazet, darren, fweisbec,
oleg, sbw
On Mon, Feb 17, 2014 at 01:40:25PM -0800, Paul E. McKenney wrote:
> From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
>
> If CONFIG_RCU_NOCB_CPU_ALL=y, then rcu_is_nocb_cpu() will always
> return true, however, the current version nevertheless checks
> rcu_nocb_mask. This commit therefore creates a static inline
> implementation of rcu_is_nocb_cpu() that unconditionally returns
> true when CONFIG_RCU_NOCB_CPU_ALL=y.
>
> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
One suggestion below. With or without that change:
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
> include/linux/rcupdate.h | 4 ++++
> kernel/rcu/tree_plugin.h | 2 ++
> 2 files changed, 6 insertions(+)
>
> diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
> index 72bf3a01a4ee..92365b1fede4 100644
> --- a/include/linux/rcupdate.h
> +++ b/include/linux/rcupdate.h
> @@ -1016,7 +1016,11 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)
> __kfree_rcu(&((ptr)->rcu_head), offsetof(typeof(*(ptr)), rcu_head))
>
> #ifdef CONFIG_RCU_NOCB_CPU
> +#ifdef CONFIG_RCU_NOCB_CPU_ALL
> +static inline bool rcu_is_nocb_cpu(int cpu) { return true; }
> +#else /* #ifdef CONFIG_RCU_NOCB_CPU_ALL */
> bool rcu_is_nocb_cpu(int cpu);
> +#endif /* #else #ifdef CONFIG_RCU_NOCB_CPU_ALL */
> #else
> static inline bool rcu_is_nocb_cpu(int cpu) { return false; }
> #endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */
This seem clearer if written without the nesting:
#if defined(CONFIG_RCU_NOCB_CPU_ALL)
static inline bool rcu_is_nocb_cpu(int cpu) { return true; }
#elif defined(CONFIG_RCU_NOCB_CPU)
bool rcu_is_nocb_cpu(int cpu);
#else
static inline bool rcu_is_nocb_cpu(int cpu) { return false; }
#endif
That clearly distinguishes the three cases: all, some, none.
> diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
> index 6e2ef4b2b920..39a50b918bff 100644
> --- a/kernel/rcu/tree_plugin.h
> +++ b/kernel/rcu/tree_plugin.h
> @@ -2101,6 +2101,7 @@ static void rcu_init_one_nocb(struct rcu_node *rnp)
> init_waitqueue_head(&rnp->nocb_gp_wq[1]);
> }
>
> +#ifndef CONFIG_RCU_NOCB_CPU_ALL
> /* Is the specified CPU a no-CPUs CPU? */
> bool rcu_is_nocb_cpu(int cpu)
> {
> @@ -2108,6 +2109,7 @@ bool rcu_is_nocb_cpu(int cpu)
> return cpumask_test_cpu(cpu, rcu_nocb_mask);
> return false;
> }
> +#endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */
>
> /*
> * Enqueue the specified string of rcu_head structures onto the specified
> --
> 1.8.1.5
>
^ permalink raw reply [flat|nested] 9+ messages in thread* Re: [PATCH tip/core/rcu 1/3] rcu: Optimize rcu_is_nocb_cpu() for RCU_NOCB_CPU_ALL
2014-02-17 21:50 ` [PATCH tip/core/rcu 1/3] rcu: Optimize rcu_is_nocb_cpu() " Josh Triplett
@ 2014-02-17 23:33 ` Paul E. McKenney
0 siblings, 0 replies; 9+ messages in thread
From: Paul E. McKenney @ 2014-02-17 23:33 UTC (permalink / raw)
To: Josh Triplett
Cc: linux-kernel, mingo, laijs, dipankar, akpm, mathieu.desnoyers,
niv, tglx, peterz, rostedt, dhowells, edumazet, darren, fweisbec,
oleg, sbw
On Mon, Feb 17, 2014 at 01:50:53PM -0800, Josh Triplett wrote:
> On Mon, Feb 17, 2014 at 01:40:25PM -0800, Paul E. McKenney wrote:
> > From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
> >
> > If CONFIG_RCU_NOCB_CPU_ALL=y, then rcu_is_nocb_cpu() will always
> > return true, however, the current version nevertheless checks
> > rcu_nocb_mask. This commit therefore creates a static inline
> > implementation of rcu_is_nocb_cpu() that unconditionally returns
> > true when CONFIG_RCU_NOCB_CPU_ALL=y.
> >
> > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
>
> One suggestion below. With or without that change:
> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
I like the change -- applied both it and your Reviewed-by.
Thanx, Paul
> > include/linux/rcupdate.h | 4 ++++
> > kernel/rcu/tree_plugin.h | 2 ++
> > 2 files changed, 6 insertions(+)
> >
> > diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
> > index 72bf3a01a4ee..92365b1fede4 100644
> > --- a/include/linux/rcupdate.h
> > +++ b/include/linux/rcupdate.h
> > @@ -1016,7 +1016,11 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)
> > __kfree_rcu(&((ptr)->rcu_head), offsetof(typeof(*(ptr)), rcu_head))
> >
> > #ifdef CONFIG_RCU_NOCB_CPU
> > +#ifdef CONFIG_RCU_NOCB_CPU_ALL
> > +static inline bool rcu_is_nocb_cpu(int cpu) { return true; }
> > +#else /* #ifdef CONFIG_RCU_NOCB_CPU_ALL */
> > bool rcu_is_nocb_cpu(int cpu);
> > +#endif /* #else #ifdef CONFIG_RCU_NOCB_CPU_ALL */
> > #else
> > static inline bool rcu_is_nocb_cpu(int cpu) { return false; }
> > #endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */
>
> This seem clearer if written without the nesting:
>
> #if defined(CONFIG_RCU_NOCB_CPU_ALL)
> static inline bool rcu_is_nocb_cpu(int cpu) { return true; }
> #elif defined(CONFIG_RCU_NOCB_CPU)
> bool rcu_is_nocb_cpu(int cpu);
> #else
> static inline bool rcu_is_nocb_cpu(int cpu) { return false; }
> #endif
>
> That clearly distinguishes the three cases: all, some, none.
>
> > diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
> > index 6e2ef4b2b920..39a50b918bff 100644
> > --- a/kernel/rcu/tree_plugin.h
> > +++ b/kernel/rcu/tree_plugin.h
> > @@ -2101,6 +2101,7 @@ static void rcu_init_one_nocb(struct rcu_node *rnp)
> > init_waitqueue_head(&rnp->nocb_gp_wq[1]);
> > }
> >
> > +#ifndef CONFIG_RCU_NOCB_CPU_ALL
> > /* Is the specified CPU a no-CPUs CPU? */
> > bool rcu_is_nocb_cpu(int cpu)
> > {
> > @@ -2108,6 +2109,7 @@ bool rcu_is_nocb_cpu(int cpu)
> > return cpumask_test_cpu(cpu, rcu_nocb_mask);
> > return false;
> > }
> > +#endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */
> >
> > /*
> > * Enqueue the specified string of rcu_head structures onto the specified
> > --
> > 1.8.1.5
> >
>
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