Re: [PATCH] srcu: Isolate srcu sections using CONFIG_SRCU
From: Mathieu Desnoyers
Date: Tue Dec 09 2014 - 15:12:25 EST
----- Original Message -----
> From: "Pranith Kumar" <bobby.prani@xxxxxxxxx>
> To: "Martin Schwidefsky" <schwidefsky@xxxxxxxxxx>, "Heiko Carstens" <heiko.carstens@xxxxxxxxxx>, "supporter:S390"
> <linux390@xxxxxxxxxx>, "Lai Jiangshan" <laijs@xxxxxxxxxxxxxx>, "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>,
> "Josh Triplett" <josh@xxxxxxxxxxxxxxxx>, "Steven Rostedt" <rostedt@xxxxxxxxxxx>, "Mathieu Desnoyers"
> <mathieu.desnoyers@xxxxxxxxxxxx>, "Christian Borntraeger" <borntraeger@xxxxxxxxxx>, "Jens Freimann"
> <jfrei@xxxxxxxxxxxxxxxxxx>, "open list:S390" <linux-s390@xxxxxxxxxxxxxxx>, "open list"
> <linux-kernel@xxxxxxxxxxxxxxx>
> Sent: Tuesday, December 9, 2014 1:48:21 PM
> Subject: [PATCH] srcu: Isolate srcu sections using CONFIG_SRCU
>
> Isolate the SRCU functions and data structures within CONFIG_SRCU so that
> there
> is a compile time failure if srcu is used when not enabled. This was decided
> to
> be better than waiting until link time for a failure to occur.
>
> Also make including kvm_host.h conditional on CONFIG_KVM being enabled. This
> prevents build failures as KVM is dependent on SRCU.
>
> Signed-off-by: Pranith Kumar <bobby.prani@xxxxxxxxx>
> CC: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
> CC: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
> CC: Lai Jiangshan <laijs@xxxxxxxxxxxxxx>
> Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
> ---
> arch/s390/kernel/asm-offsets.c | 7 ++++++-
> include/linux/notifier.h | 47
> ++++++++++++++++++++++++------------------
> include/linux/srcu.h | 6 +++++-
> 3 files changed, 38 insertions(+), 22 deletions(-)
>
> diff --git a/arch/s390/kernel/asm-offsets.c b/arch/s390/kernel/asm-offsets.c
> index ef279a1..2813a3c 100644
> --- a/arch/s390/kernel/asm-offsets.c
> +++ b/arch/s390/kernel/asm-offsets.c
> @@ -7,12 +7,15 @@
> #define ASM_OFFSETS_C
>
> #include <linux/kbuild.h>
> -#include <linux/kvm_host.h>
> #include <linux/sched.h>
> #include <asm/idle.h>
> #include <asm/vdso.h>
> #include <asm/pgtable.h>
>
> +#if IS_ENABLED(CONFIG_KVM)
> +#include <linux/kvm_host.h>
> +#endif
> +
Seeing this kind of conditional include makes me cringe. Is there some
way to hide this within linux/kvm_host.h instead ?
Thanks,
Mathieu
> /*
> * Make sure that the compiler is new enough. We want a compiler that
> * is known to work with the "Q" assembler constraint.
> @@ -182,8 +185,10 @@ int main(void)
> DEFINE(__LC_PGM_TDB, offsetof(struct _lowcore, pgm_tdb));
> DEFINE(__THREAD_trap_tdb, offsetof(struct task_struct, thread.trap_tdb));
> DEFINE(__GMAP_ASCE, offsetof(struct gmap, asce));
> +#if IS_ENABLED(CONFIG_KVM)
> DEFINE(__SIE_PROG0C, offsetof(struct kvm_s390_sie_block, prog0c));
> DEFINE(__SIE_PROG20, offsetof(struct kvm_s390_sie_block, prog20));
> +#endif /* CONFIG_KVM */
> #endif /* CONFIG_32BIT */
> return 0;
> }
> diff --git a/include/linux/notifier.h b/include/linux/notifier.h
> index d14a4c3..fe4f02a 100644
> --- a/include/linux/notifier.h
> +++ b/include/linux/notifier.h
> @@ -47,6 +47,8 @@
> * runtime initialization.
> */
>
> +struct notifier_block;
> +
> typedef int (*notifier_fn_t)(struct notifier_block *nb,
> unsigned long action, void *data);
>
> @@ -70,12 +72,6 @@ struct raw_notifier_head {
> struct notifier_block __rcu *head;
> };
>
> -struct srcu_notifier_head {
> - struct mutex mutex;
> - struct srcu_struct srcu;
> - struct notifier_block __rcu *head;
> -};
> -
> #define ATOMIC_INIT_NOTIFIER_HEAD(name) do { \
> spin_lock_init(&(name)->lock); \
> (name)->head = NULL; \
> @@ -88,11 +84,6 @@ struct srcu_notifier_head {
> (name)->head = NULL; \
> } while (0)
>
> -/* srcu_notifier_heads must be initialized and cleaned up dynamically */
> -extern void srcu_init_notifier_head(struct srcu_notifier_head *nh);
> -#define srcu_cleanup_notifier_head(name) \
> - cleanup_srcu_struct(&(name)->srcu);
> -
> #define ATOMIC_NOTIFIER_INIT(name) { \
> .lock = __SPIN_LOCK_UNLOCKED(name.lock), \
> .head = NULL }
> @@ -101,7 +92,6 @@ extern void srcu_init_notifier_head(struct
> srcu_notifier_head *nh);
> .head = NULL }
> #define RAW_NOTIFIER_INIT(name) { \
> .head = NULL }
> -/* srcu_notifier_heads cannot be initialized statically */
>
> #define ATOMIC_NOTIFIER_HEAD(name) \
> struct atomic_notifier_head name = \
> @@ -121,8 +111,6 @@ extern int blocking_notifier_chain_register(struct
> blocking_notifier_head *nh,
> struct notifier_block *nb);
> extern int raw_notifier_chain_register(struct raw_notifier_head *nh,
> struct notifier_block *nb);
> -extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh,
> - struct notifier_block *nb);
>
> extern int blocking_notifier_chain_cond_register(
> struct blocking_notifier_head *nh,
> @@ -134,8 +122,6 @@ extern int blocking_notifier_chain_unregister(struct
> blocking_notifier_head *nh,
> struct notifier_block *nb);
> extern int raw_notifier_chain_unregister(struct raw_notifier_head *nh,
> struct notifier_block *nb);
> -extern int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh,
> - struct notifier_block *nb);
>
> extern int atomic_notifier_call_chain(struct atomic_notifier_head *nh,
> unsigned long val, void *v);
> @@ -149,10 +135,6 @@ extern int raw_notifier_call_chain(struct
> raw_notifier_head *nh,
> unsigned long val, void *v);
> extern int __raw_notifier_call_chain(struct raw_notifier_head *nh,
> unsigned long val, void *v, int nr_to_call, int *nr_calls);
> -extern int srcu_notifier_call_chain(struct srcu_notifier_head *nh,
> - unsigned long val, void *v);
> -extern int __srcu_notifier_call_chain(struct srcu_notifier_head *nh,
> - unsigned long val, void *v, int nr_to_call, int *nr_calls);
>
> #define NOTIFY_DONE 0x0000 /* Don't care */
> #define NOTIFY_OK 0x0001 /* Suits me */
> @@ -211,5 +193,30 @@ static inline int notifier_to_errno(int ret)
>
> extern struct blocking_notifier_head reboot_notifier_list;
>
> +#ifdef CONFIG_SRCU
> +
> +struct srcu_notifier_head {
> + struct mutex mutex;
> + struct srcu_struct srcu;
> + struct notifier_block __rcu *head;
> +};
> +
> +/* srcu_notifier_heads must be initialized and cleaned up dynamically
> + * srcu_notifier_heads cannot be initialized statically
> + */
> +extern void srcu_init_notifier_head(struct srcu_notifier_head *nh);
> +#define srcu_cleanup_notifier_head(name) cleanup_srcu_struct(&(name)->srcu)
> +
> +extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh,
> + struct notifier_block *nb);
> +extern int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh,
> + struct notifier_block *nb);
> +extern int srcu_notifier_call_chain(struct srcu_notifier_head *nh,
> + unsigned long val, void *v);
> +extern int __srcu_notifier_call_chain(struct srcu_notifier_head *nh,
> + unsigned long val, void *v, int nr_to_call, int *nr_calls);
> +
> +#endif /* CONFIG_SRCU */
> +
> #endif /* __KERNEL__ */
> #endif /* _LINUX_NOTIFIER_H */
> diff --git a/include/linux/srcu.h b/include/linux/srcu.h
> index 9cfd962..ed9c389 100644
> --- a/include/linux/srcu.h
> +++ b/include/linux/srcu.h
> @@ -26,6 +26,8 @@
> *
> */
>
> +#ifdef CONFIG_SRCU
> +
> #ifndef _LINUX_SRCU_H
> #define _LINUX_SRCU_H
>
> @@ -249,4 +251,6 @@ static inline void smp_mb__after_srcu_read_unlock(void)
> /* __srcu_read_unlock has smp_mb() internally so nothing to do here. */
> }
>
> -#endif
> +#endif /* _LINUX_SRCU_H */
> +
> +#endif /* CONFIG_SRCU */
> --
> 1.9.1
>
>
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
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