Messages in this thread | | | Date | Wed, 24 Jan 2018 22:20:31 -0800 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH RFC 07/16] prcu: Implement call_prcu() API |
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On Tue, Jan 23, 2018 at 03:59:32PM +0800, lianglihao@huawei.com wrote: > From: Lihao Liang <lianglihao@huawei.com> > > This is PRCU's counterpart of RCU's call_rcu() API. > > Reviewed-by: Heng Zhang <heng.z@huawei.com> > Signed-off-by: Lihao Liang <lianglihao@huawei.com> > --- > include/linux/prcu.h | 25 ++++++++++++++++++++ > init/main.c | 2 ++ > kernel/rcu/prcu.c | 67 +++++++++++++++++++++++++++++++++++++++++++++++++--- > 3 files changed, 91 insertions(+), 3 deletions(-) > > diff --git a/include/linux/prcu.h b/include/linux/prcu.h > index 653b4633..e5e09c9b 100644 > --- a/include/linux/prcu.h > +++ b/include/linux/prcu.h > @@ -2,15 +2,36 @@ > #define __LINUX_PRCU_H > > #include <linux/atomic.h> > +#include <linux/types.h> > #include <linux/mutex.h> > #include <linux/wait.h> > > #define CONFIG_PRCU > > +struct prcu_version_head { > + unsigned long long version; > + struct prcu_version_head *next; > +}; > + > +/* Simple unsegmented callback list for PRCU. */ > +struct prcu_cblist { > + struct rcu_head *head; > + struct rcu_head **tail; > + struct prcu_version_head *version_head; > + struct prcu_version_head **version_tail; > + long len; > +}; > + > +#define PRCU_CBLIST_INITIALIZER(n) { \ > + .head = NULL, .tail = &n.head, \ > + .version_head = NULL, .version_tail = &n.version_head, \ > +} > + > struct prcu_local_struct { > unsigned int locked; > unsigned int online; > unsigned long long version; > + struct prcu_cblist cblist; > }; > > struct prcu_struct { > @@ -24,6 +45,8 @@ struct prcu_struct { > void prcu_read_lock(void); > void prcu_read_unlock(void); > void synchronize_prcu(void); > +void call_prcu(struct rcu_head *head, rcu_callback_t func); > +void prcu_init(void); > void prcu_note_context_switch(void); > > #else /* #ifdef CONFIG_PRCU */ > @@ -31,6 +54,8 @@ void prcu_note_context_switch(void); > #define prcu_read_lock() do {} while (0) > #define prcu_read_unlock() do {} while (0) > #define synchronize_prcu() do {} while (0) > +#define call_prcu() do {} while (0) > +#define prcu_init() do {} while (0) > #define prcu_note_context_switch() do {} while (0) > > #endif /* #ifdef CONFIG_PRCU */ > diff --git a/init/main.c b/init/main.c > index f8665104..4925964e 100644 > --- a/init/main.c > +++ b/init/main.c > @@ -38,6 +38,7 @@ > #include <linux/smp.h> > #include <linux/profile.h> > #include <linux/rcupdate.h> > +#include <linux/prcu.h> > #include <linux/moduleparam.h> > #include <linux/kallsyms.h> > #include <linux/writeback.h> > @@ -574,6 +575,7 @@ asmlinkage __visible void __init start_kernel(void) > workqueue_init_early(); > > rcu_init(); > + prcu_init(); > > /* Trace events are available after this */ > trace_init(); > diff --git a/kernel/rcu/prcu.c b/kernel/rcu/prcu.c > index a00b9420..f198285c 100644 > --- a/kernel/rcu/prcu.c > +++ b/kernel/rcu/prcu.c > @@ -1,11 +1,12 @@ > #include <linux/smp.h> > -#include <linux/prcu.h> > #include <linux/percpu.h> > -#include <linux/compiler.h> > +#include <linux/prcu.h> > #include <linux/sched.h> > - > +#include <linux/slab.h> > #include <asm/barrier.h> > > +#include "rcu.h" > + > DEFINE_PER_CPU_SHARED_ALIGNED(struct prcu_local_struct, prcu_local); > > struct prcu_struct global_prcu = { > @@ -16,6 +17,16 @@ struct prcu_struct global_prcu = { > }; > struct prcu_struct *prcu = &global_prcu; > > +/* Initialize simple callback list. */ > +static void prcu_cblist_init(struct prcu_cblist *rclp) > +{ > + rclp->head = NULL; > + rclp->tail = &rclp->head; > + rclp->version_head = NULL; > + rclp->version_tail = &rclp->version_head; > + rclp->len = 0; > +} > + > static inline void prcu_report(struct prcu_local_struct *local) > { > unsigned long long global_version; > @@ -123,3 +134,53 @@ void prcu_note_context_switch(void) > prcu_report(local); > put_cpu_ptr(&prcu_local); > } > + > +void call_prcu(struct rcu_head *head, rcu_callback_t func) > +{ > + unsigned long flags; > + struct prcu_local_struct *local; > + struct prcu_cblist *rclp; > + struct prcu_version_head *vhp; > + > + debug_rcu_head_queue(head); > + > + /* Use GFP_ATOMIC with IRQs disabled */ > + vhp = kmalloc(sizeof(struct prcu_version_head), GFP_ATOMIC); > + if (!vhp) > + return;
Silently failing to post the callback can cause system hangs. I suggest finding some way to avoid allocating on the call_prcu() code path.
Thanx, Paul
> + > + head->func = func; > + head->next = NULL; > + vhp->next = NULL; > + > + local_irq_save(flags); > + local = this_cpu_ptr(&prcu_local); > + vhp->version = local->version; > + rclp = &local->cblist; > + rclp->len++; > + *rclp->tail = head; > + rclp->tail = &head->next; > + *rclp->version_tail = vhp; > + rclp->version_tail = &vhp->next; > + local_irq_restore(flags); > +} > +EXPORT_SYMBOL(call_prcu); > + > +void prcu_init_local_struct(int cpu) > +{ > + struct prcu_local_struct *local; > + > + local = per_cpu_ptr(&prcu_local, cpu); > + local->locked = 0; > + local->online = 0; > + local->version = 0; > + prcu_cblist_init(&local->cblist); > +} > + > +void __init prcu_init(void) > +{ > + int cpu; > + > + for_each_possible_cpu(cpu) > + prcu_init_local_struct(cpu); > +} > -- > 2.14.1.729.g59c0ea183 >
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