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Message-ID: <20090828021651.GA31575@Krystal>
Date: Thu, 27 Aug 2009 22:16:51 -0400
From: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc: linux-kernel@...r.kernel.org, mingo@...e.hu, laijs@...fujitsu.com,
dipankar@...ibm.com, akpm@...ux-foundation.org,
josht@...ux.vnet.ibm.com, dvhltc@...ibm.com, niv@...ibm.com,
tglx@...utronix.de, peterz@...radead.org, rostedt@...dmis.org
Subject: Re: [PATCH tip/core/rcu] Changes from reviews: avoid casts,
fix/add warnings, improve comments.
* Paul E. McKenney (paulmck@...ux.vnet.ibm.com) wrote:
> Changes suggested by review comments from Josh Triplett and Mathieu
> Desnoyers.
>
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
> Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> ---
>
> include/linux/sched.h | 4 +++-
> kernel/rcutree.c | 13 ++++++-------
> kernel/rcutree.h | 2 ++
> kernel/rcutree_plugin.h | 10 ++++++----
> 4 files changed, 17 insertions(+), 12 deletions(-)
>
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index 3fe0315..855fd0d 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -1163,6 +1163,8 @@ struct sched_rt_entity {
> #endif
> };
>
> +struct rcu_node;
> +
> struct task_struct {
> volatile long state; /* -1 unrunnable, 0 runnable, >0 stopped */
> void *stack;
> @@ -1208,7 +1210,7 @@ struct task_struct {
> #ifdef CONFIG_TREE_PREEMPT_RCU
> int rcu_read_lock_nesting;
> char rcu_read_unlock_special;
> - void *rcu_blocked_node;
> + struct rcu_node *rcu_blocked_node;
> struct list_head rcu_node_entry;
> #endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
>
> diff --git a/kernel/rcutree.c b/kernel/rcutree.c
> index d903e2f..71bc797 100644
> --- a/kernel/rcutree.c
> +++ b/kernel/rcutree.c
> @@ -229,7 +229,6 @@ static int rcu_implicit_offline_qs(struct rcu_data *rdp)
> #endif /* #ifdef CONFIG_SMP */
>
> #ifdef CONFIG_NO_HZ
> -static DEFINE_RATELIMIT_STATE(rcu_rs, 10 * HZ, 5);
>
> /**
> * 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->dynticks++;
> rdtp->dynticks_nesting--;
> - WARN_ON_RATELIMIT(rdtp->dynticks & 0x1, &rcu_rs);
> + WARN_ON_ONCE(rdtp->dynticks & 0x1);
> local_irq_restore(flags);
> }
>
> @@ -268,7 +267,7 @@ void rcu_exit_nohz(void)
> rdtp = &__get_cpu_var(rcu_dynticks);
> rdtp->dynticks++;
> rdtp->dynticks_nesting++;
> - WARN_ON_RATELIMIT(!(rdtp->dynticks & 0x1), &rcu_rs);
> + WARN_ON_ONCE(!(rdtp->dynticks & 0x1));
> local_irq_restore(flags);
> 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)
> return;
> 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 */
> }
>
> @@ -306,7 +305,7 @@ void rcu_nmi_exit(void)
> return;
> smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */
> 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++)
> return;
> 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 */
> }
>
> @@ -341,7 +340,7 @@ void rcu_irq_exit(void)
> return;
> smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */
> 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 (__get_cpu_var(rcu_sched_data).nxtlist ||
> diff --git a/kernel/rcutree.h b/kernel/rcutree.h
> index ca56036..bf8a6f9 100644
> --- a/kernel/rcutree.h
> +++ b/kernel/rcutree.h
> @@ -81,6 +81,8 @@ struct rcu_dynticks {
> struct rcu_node {
> spinlock_t lock;
> 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 */
> /* order for current grace period to proceed.*/
> unsigned long qsmaskinit;
> diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
> index 04343be..4778936 100644
> --- a/kernel/rcutree_plugin.h
> +++ b/kernel/rcutree_plugin.h
> @@ -92,7 +92,7 @@ static void rcu_preempt_qs(int cpu)
> rnp = rdp->mynode;
> spin_lock(&rnp->lock);
> 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
> @@ -176,9 +176,9 @@ static void rcu_read_unlock_special(struct task_struct *t)
> * most one time. So at most two passes through loop.
> */
> for (;;) {
> - rnp = (struct rcu_node *)t->rcu_blocked_node;
> + rnp = t->rcu_blocked_node;
> spin_lock(&rnp->lock);
> - if (rnp == (struct rcu_node *)t->rcu_blocked_node)
> + if (rnp == t->rcu_blocked_node)
> break;
> 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 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. */
> + }
>
> /*
> * Move tasks up to root rcu_node. Rely on the fact that the
--
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
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