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rcu: Introduce for_each_rcu_flavor() and use it
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The arrival of TREE_PREEMPT_RCU some years back included some ugly
code involving either #ifdef or #ifdef'ed wrapper functions to iterate
over all non-SRCU flavors of RCU.  This commit therefore introduces
a for_each_rcu_flavor() iterator over the rcu_state structures for each
flavor of RCU to clean up a bit of the ugliness.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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Paul E. McKenney committed Jul 2, 2012
1 parent 1bca8cf commit 6ce75a2
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Showing 3 changed files with 37 additions and 144 deletions.
53 changes: 32 additions & 21 deletions kernel/rcutree.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -84,6 +84,7 @@ struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh, call_rcu_bh);
DEFINE_PER_CPU(struct rcu_data, rcu_bh_data);

static struct rcu_state *rcu_state;
LIST_HEAD(rcu_struct_flavors);

/* Increase (but not decrease) the CONFIG_RCU_FANOUT_LEAF at boot time. */
static int rcu_fanout_leaf = CONFIG_RCU_FANOUT_LEAF;
Expand Down Expand Up @@ -860,9 +861,10 @@ static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr)
*/
void rcu_cpu_stall_reset(void)
{
rcu_sched_state.jiffies_stall = jiffies + ULONG_MAX / 2;
rcu_bh_state.jiffies_stall = jiffies + ULONG_MAX / 2;
rcu_preempt_stall_reset();
struct rcu_state *rsp;

for_each_rcu_flavor(rsp)
rsp->jiffies_stall = jiffies + ULONG_MAX / 2;
}

static struct notifier_block rcu_panic_block = {
Expand Down Expand Up @@ -1827,10 +1829,11 @@ __rcu_process_callbacks(struct rcu_state *rsp)
*/
static void rcu_process_callbacks(struct softirq_action *unused)
{
struct rcu_state *rsp;

trace_rcu_utilization("Start RCU core");
__rcu_process_callbacks(&rcu_sched_state);
__rcu_process_callbacks(&rcu_bh_state);
rcu_preempt_process_callbacks();
for_each_rcu_flavor(rsp)
__rcu_process_callbacks(rsp);
trace_rcu_utilization("End RCU core");
}

Expand Down Expand Up @@ -2241,9 +2244,12 @@ static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp)
*/
static int rcu_pending(int cpu)
{
return __rcu_pending(&rcu_sched_state, &per_cpu(rcu_sched_data, cpu)) ||
__rcu_pending(&rcu_bh_state, &per_cpu(rcu_bh_data, cpu)) ||
rcu_preempt_pending(cpu);
struct rcu_state *rsp;

for_each_rcu_flavor(rsp)
if (__rcu_pending(rsp, per_cpu_ptr(rsp->rda, cpu)))
return 1;
return 0;
}

/*
Expand All @@ -2253,10 +2259,13 @@ static int rcu_pending(int cpu)
*/
static int rcu_cpu_has_callbacks(int cpu)
{
struct rcu_state *rsp;

/* RCU callbacks either ready or pending? */
return per_cpu(rcu_sched_data, cpu).nxtlist ||
per_cpu(rcu_bh_data, cpu).nxtlist ||
rcu_preempt_cpu_has_callbacks(cpu);
for_each_rcu_flavor(rsp)
if (per_cpu_ptr(rsp->rda, cpu)->nxtlist)
return 1;
return 0;
}

/*
Expand Down Expand Up @@ -2551,9 +2560,11 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptible)

static void __cpuinit rcu_prepare_cpu(int cpu)
{
rcu_init_percpu_data(cpu, &rcu_sched_state, 0);
rcu_init_percpu_data(cpu, &rcu_bh_state, 0);
rcu_preempt_init_percpu_data(cpu);
struct rcu_state *rsp;

for_each_rcu_flavor(rsp)
rcu_init_percpu_data(cpu, rsp,
strcmp(rsp->name, "rcu_preempt") == 0);
}

/*
Expand All @@ -2565,6 +2576,7 @@ static int __cpuinit rcu_cpu_notify(struct notifier_block *self,
long cpu = (long)hcpu;
struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu);
struct rcu_node *rnp = rdp->mynode;
struct rcu_state *rsp;

trace_rcu_utilization("Start CPU hotplug");
switch (action) {
Expand All @@ -2589,18 +2601,16 @@ static int __cpuinit rcu_cpu_notify(struct notifier_block *self,
* touch any data without introducing corruption. We send the
* dying CPU's callbacks to an arbitrarily chosen online CPU.
*/
rcu_cleanup_dying_cpu(&rcu_bh_state);
rcu_cleanup_dying_cpu(&rcu_sched_state);
rcu_preempt_cleanup_dying_cpu();
for_each_rcu_flavor(rsp)
rcu_cleanup_dying_cpu(rsp);
rcu_cleanup_after_idle(cpu);
break;
case CPU_DEAD:
case CPU_DEAD_FROZEN:
case CPU_UP_CANCELED:
case CPU_UP_CANCELED_FROZEN:
rcu_cleanup_dead_cpu(cpu, &rcu_bh_state);
rcu_cleanup_dead_cpu(cpu, &rcu_sched_state);
rcu_preempt_cleanup_dead_cpu(cpu);
for_each_rcu_flavor(rsp)
rcu_cleanup_dead_cpu(cpu, rsp);
break;
default:
break;
Expand Down Expand Up @@ -2717,6 +2727,7 @@ static void __init rcu_init_one(struct rcu_state *rsp,
per_cpu_ptr(rsp->rda, i)->mynode = rnp;
rcu_boot_init_percpu_data(i, rsp);
}
list_add(&rsp->flavors, &rcu_struct_flavors);
}

/*
Expand Down
12 changes: 5 additions & 7 deletions kernel/rcutree.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -422,8 +422,13 @@ struct rcu_state {
unsigned long gp_max; /* Maximum GP duration in */
/* jiffies. */
char *name; /* Name of structure. */
struct list_head flavors; /* List of RCU flavors. */
};

extern struct list_head rcu_struct_flavors;
#define for_each_rcu_flavor(rsp) \
list_for_each_entry((rsp), &rcu_struct_flavors, flavors)

/* Return values for rcu_preempt_offline_tasks(). */

#define RCU_OFL_TASKS_NORM_GP 0x1 /* Tasks blocking normal */
Expand Down Expand Up @@ -466,25 +471,18 @@ static void rcu_stop_cpu_kthread(int cpu);
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
static void rcu_print_detail_task_stall(struct rcu_state *rsp);
static int rcu_print_task_stall(struct rcu_node *rnp);
static void rcu_preempt_stall_reset(void);
static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp);
#ifdef CONFIG_HOTPLUG_CPU
static int rcu_preempt_offline_tasks(struct rcu_state *rsp,
struct rcu_node *rnp,
struct rcu_data *rdp);
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
static void rcu_preempt_cleanup_dead_cpu(int cpu);
static void rcu_preempt_check_callbacks(int cpu);
static void rcu_preempt_process_callbacks(void);
void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu));
#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_TREE_PREEMPT_RCU)
static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
bool wake);
#endif /* #if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_TREE_PREEMPT_RCU) */
static int rcu_preempt_pending(int cpu);
static int rcu_preempt_cpu_has_callbacks(int cpu);
static void __cpuinit rcu_preempt_init_percpu_data(int cpu);
static void rcu_preempt_cleanup_dying_cpu(void);
static void __init __rcu_init_preempt(void);
static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags);
static void rcu_preempt_boost_start_gp(struct rcu_node *rnp);
Expand Down
116 changes: 0 additions & 116 deletions kernel/rcutree_plugin.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -544,16 +544,6 @@ static int rcu_print_task_stall(struct rcu_node *rnp)
return ndetected;
}

/*
* Suppress preemptible RCU's CPU stall warnings by pushing the
* time of the next stall-warning message comfortably far into the
* future.
*/
static void rcu_preempt_stall_reset(void)
{
rcu_preempt_state.jiffies_stall = jiffies + ULONG_MAX / 2;
}

/*
* Check that the list of blocked tasks for the newly completed grace
* period is in fact empty. It is a serious bug to complete a grace
Expand Down Expand Up @@ -654,14 +644,6 @@ static int rcu_preempt_offline_tasks(struct rcu_state *rsp,

#endif /* #ifdef CONFIG_HOTPLUG_CPU */

/*
* Do CPU-offline processing for preemptible RCU.
*/
static void rcu_preempt_cleanup_dead_cpu(int cpu)
{
rcu_cleanup_dead_cpu(cpu, &rcu_preempt_state);
}

/*
* Check for a quiescent state from the current CPU. When a task blocks,
* the task is recorded in the corresponding CPU's rcu_node structure,
Expand All @@ -682,14 +664,6 @@ static void rcu_preempt_check_callbacks(int cpu)
t->rcu_read_unlock_special |= RCU_READ_UNLOCK_NEED_QS;
}

/*
* Process callbacks for preemptible RCU.
*/
static void rcu_preempt_process_callbacks(void)
{
__rcu_process_callbacks(&rcu_preempt_state);
}

#ifdef CONFIG_RCU_BOOST

static void rcu_preempt_do_callbacks(void)
Expand Down Expand Up @@ -921,24 +895,6 @@ void synchronize_rcu_expedited(void)
}
EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);

/*
* Check to see if there is any immediate preemptible-RCU-related work
* to be done.
*/
static int rcu_preempt_pending(int cpu)
{
return __rcu_pending(&rcu_preempt_state,
&per_cpu(rcu_preempt_data, cpu));
}

/*
* Does preemptible RCU have callbacks on this CPU?
*/
static int rcu_preempt_cpu_has_callbacks(int cpu)
{
return !!per_cpu(rcu_preempt_data, cpu).nxtlist;
}

/**
* rcu_barrier - Wait until all in-flight call_rcu() callbacks complete.
*/
Expand All @@ -948,23 +904,6 @@ void rcu_barrier(void)
}
EXPORT_SYMBOL_GPL(rcu_barrier);

/*
* Initialize preemptible RCU's per-CPU data.
*/
static void __cpuinit rcu_preempt_init_percpu_data(int cpu)
{
rcu_init_percpu_data(cpu, &rcu_preempt_state, 1);
}

/*
* Move preemptible RCU's callbacks from dying CPU to other online CPU
* and record a quiescent state.
*/
static void rcu_preempt_cleanup_dying_cpu(void)
{
rcu_cleanup_dying_cpu(&rcu_preempt_state);
}

/*
* Initialize preemptible RCU's state structures.
*/
Expand Down Expand Up @@ -1049,14 +988,6 @@ static int rcu_print_task_stall(struct rcu_node *rnp)
return 0;
}

/*
* Because preemptible RCU does not exist, there is no need to suppress
* its CPU stall warnings.
*/
static void rcu_preempt_stall_reset(void)
{
}

/*
* Because there is no preemptible RCU, there can be no readers blocked,
* so there is no need to check for blocked tasks. So check only for
Expand Down Expand Up @@ -1084,14 +1015,6 @@ static int rcu_preempt_offline_tasks(struct rcu_state *rsp,

#endif /* #ifdef CONFIG_HOTPLUG_CPU */

/*
* Because preemptible RCU does not exist, it never needs CPU-offline
* processing.
*/
static void rcu_preempt_cleanup_dead_cpu(int cpu)
{
}

/*
* Because preemptible RCU does not exist, it never has any callbacks
* to check.
Expand All @@ -1100,14 +1023,6 @@ static void rcu_preempt_check_callbacks(int cpu)
{
}

/*
* Because preemptible RCU does not exist, it never has any callbacks
* to process.
*/
static void rcu_preempt_process_callbacks(void)
{
}

/*
* Queue an RCU callback for lazy invocation after a grace period.
* This will likely be later named something like "call_rcu_lazy()",
Expand Down Expand Up @@ -1148,22 +1063,6 @@ static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,

#endif /* #ifdef CONFIG_HOTPLUG_CPU */

/*
* Because preemptible RCU does not exist, it never has any work to do.
*/
static int rcu_preempt_pending(int cpu)
{
return 0;
}

/*
* Because preemptible RCU does not exist, it never has callbacks
*/
static int rcu_preempt_cpu_has_callbacks(int cpu)
{
return 0;
}

/*
* Because preemptible RCU does not exist, rcu_barrier() is just
* another name for rcu_barrier_sched().
Expand All @@ -1174,21 +1073,6 @@ void rcu_barrier(void)
}
EXPORT_SYMBOL_GPL(rcu_barrier);

/*
* Because preemptible RCU does not exist, there is no per-CPU
* data to initialize.
*/
static void __cpuinit rcu_preempt_init_percpu_data(int cpu)
{
}

/*
* Because there is no preemptible RCU, there is no cleanup to do.
*/
static void rcu_preempt_cleanup_dying_cpu(void)
{
}

/*
* Because preemptible RCU does not exist, it need not be initialized.
*/
Expand Down

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