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rcu: Changes from reviews: avoid casts, fix/add warnings, improve comments

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Changes suggested by review comments from Josh Triplett and
Mathieu Desnoyers.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Josh Triplett <josh@joshtriplett.org>
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: akpm@linux-foundation.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
LKML-Reference: <20090827220012.GA30525@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Paul E. McKenney 2009-08-27 15:00:12 -07:00 committed by Ingo Molnar
parent dd5d19bafd
commit 868489660d
4 changed files with 17 additions and 12 deletions
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4
include/linux/sched.h
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@ -1163,6 +1163,8 @@ struct sched_rt_entity {
#endif #endif
}; };
struct rcu_node;
struct task_struct { struct task_struct {
volatile long state; /* -1 unrunnable, 0 runnable, >0 stopped */ volatile long state; /* -1 unrunnable, 0 runnable, >0 stopped */
void *stack; void *stack;
@ -1208,7 +1210,7 @@ struct task_struct {
#ifdef CONFIG_TREE_PREEMPT_RCU #ifdef CONFIG_TREE_PREEMPT_RCU
int rcu_read_lock_nesting; int rcu_read_lock_nesting;
char rcu_read_unlock_special; char rcu_read_unlock_special;
void *rcu_blocked_node; struct rcu_node *rcu_blocked_node;
struct list_head rcu_node_entry; struct list_head rcu_node_entry;
#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */ #endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */

13
kernel/rcutree.c
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@ -229,7 +229,6 @@ static int rcu_implicit_offline_qs(struct rcu_data *rdp)
#endif /* #ifdef CONFIG_SMP */ #endif /* #ifdef CONFIG_SMP */
#ifdef CONFIG_NO_HZ #ifdef CONFIG_NO_HZ
static DEFINE_RATELIMIT_STATE(rcu_rs, 10 * HZ, 5);
/** /**
* rcu_enter_nohz - inform RCU that current CPU is entering nohz * rcu_enter_nohz - inform RCU that current CPU is entering nohz
@ -249,7 +248,7 @@ void rcu_enter_nohz(void)
rdtp = &__get_cpu_var(rcu_dynticks); rdtp = &__get_cpu_var(rcu_dynticks);
rdtp->dynticks++; rdtp->dynticks++;
rdtp->dynticks_nesting--; rdtp->dynticks_nesting--;
WARN_ON_RATELIMIT(rdtp->dynticks & 0x1, &rcu_rs); WARN_ON_ONCE(rdtp->dynticks & 0x1);
local_irq_restore(flags); local_irq_restore(flags);
} }
@ -268,7 +267,7 @@ void rcu_exit_nohz(void)
rdtp = &__get_cpu_var(rcu_dynticks); rdtp = &__get_cpu_var(rcu_dynticks);
rdtp->dynticks++; rdtp->dynticks++;
rdtp->dynticks_nesting++; rdtp->dynticks_nesting++;
WARN_ON_RATELIMIT(!(rdtp->dynticks & 0x1), &rcu_rs); WARN_ON_ONCE(!(rdtp->dynticks & 0x1));
local_irq_restore(flags); local_irq_restore(flags);
smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */
} }
@ -287,7 +286,7 @@ void rcu_nmi_enter(void)
if (rdtp->dynticks & 0x1) if (rdtp->dynticks & 0x1)
return; return;
rdtp->dynticks_nmi++; rdtp->dynticks_nmi++;
WARN_ON_RATELIMIT(!(rdtp->dynticks_nmi & 0x1), &rcu_rs); WARN_ON_ONCE(!(rdtp->dynticks_nmi & 0x1));
smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */
} }
@ -306,7 +305,7 @@ void rcu_nmi_exit(void)
return; return;
smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */ smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */
rdtp->dynticks_nmi++; rdtp->dynticks_nmi++;
WARN_ON_RATELIMIT(rdtp->dynticks_nmi & 0x1, &rcu_rs); WARN_ON_ONCE(rdtp->dynticks_nmi & 0x1);
} }
/** /**
@ -322,7 +321,7 @@ void rcu_irq_enter(void)
if (rdtp->dynticks_nesting++) if (rdtp->dynticks_nesting++)
return; return;
rdtp->dynticks++; rdtp->dynticks++;
WARN_ON_RATELIMIT(!(rdtp->dynticks & 0x1), &rcu_rs); WARN_ON_ONCE(!(rdtp->dynticks & 0x1));
smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */
} }
@ -341,7 +340,7 @@ void rcu_irq_exit(void)
return; return;
smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */ smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */
rdtp->dynticks++; rdtp->dynticks++;
WARN_ON_RATELIMIT(rdtp->dynticks & 0x1, &rcu_rs); WARN_ON_ONCE(rdtp->dynticks & 0x1);
/* If the interrupt queued a callback, get out of dyntick mode. */ /* If the interrupt queued a callback, get out of dyntick mode. */
if (__get_cpu_var(rcu_sched_data).nxtlist || if (__get_cpu_var(rcu_sched_data).nxtlist ||

2
kernel/rcutree.h
View File

@ -81,6 +81,8 @@ struct rcu_dynticks {
struct rcu_node { struct rcu_node {
spinlock_t lock; spinlock_t lock;
long gpnum; /* Current grace period for this node. */ long gpnum; /* Current grace period for this node. */
/* This will either be equal to or one */
/* behind the root rcu_node's gpnum. */
unsigned long qsmask; /* CPUs or groups that need to switch in */ unsigned long qsmask; /* CPUs or groups that need to switch in */
/* order for current grace period to proceed.*/ /* order for current grace period to proceed.*/
unsigned long qsmaskinit; unsigned long qsmaskinit;

10
kernel/rcutree_plugin.h
View File

@ -92,7 +92,7 @@ static void rcu_preempt_qs(int cpu)
rnp = rdp->mynode; rnp = rdp->mynode;
spin_lock(&rnp->lock); spin_lock(&rnp->lock);
t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BLOCKED; t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BLOCKED;
t->rcu_blocked_node = (void *)rnp; t->rcu_blocked_node = rnp;
/* /*
* If this CPU has already checked in, then this task * If this CPU has already checked in, then this task
@ -176,9 +176,9 @@ static void rcu_read_unlock_special(struct task_struct *t)
* most one time. So at most two passes through loop. * most one time. So at most two passes through loop.
*/ */
for (;;) { for (;;) {
rnp = (struct rcu_node *)t->rcu_blocked_node; rnp = t->rcu_blocked_node;
spin_lock(&rnp->lock); spin_lock(&rnp->lock);
if (rnp == (struct rcu_node *)t->rcu_blocked_node) if (rnp == t->rcu_blocked_node)
break; break;
spin_unlock(&rnp->lock); spin_unlock(&rnp->lock);
} }
@ -288,8 +288,10 @@ static void rcu_preempt_offline_tasks(struct rcu_state *rsp,
struct rcu_node *rnp_root = rcu_get_root(rsp); struct rcu_node *rnp_root = rcu_get_root(rsp);
struct task_struct *tp; struct task_struct *tp;
if (rnp == rnp_root) if (rnp == rnp_root) {
WARN_ONCE(1, "Last CPU thought to be offlined?");
return; /* Shouldn't happen: at least one CPU online. */ return; /* Shouldn't happen: at least one CPU online. */
}
/* /*
* Move tasks up to root rcu_node. Rely on the fact that the * Move tasks up to root rcu_node. Rely on the fact that the