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[PATCH] rcu: join rcu_ctrlblk and rcu_state
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This patch moves rcu_state into the rcu_ctrlblk. I think there
are no reasons why we should have 2 different variables to control
rcu state. Every user of rcu_state has also "rcu_ctrlblk *rcp" in
the parameter list.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Paul E. McKenney <paulmck@us.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Oleg Nesterov authored and Linus Torvalds committed Jan 10, 2006
1 parent c0400dc commit 69a0b31
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Showing 2 changed files with 42 additions and 44 deletions.
4 changes: 4 additions & 0 deletions include/linux/rcupdate.h
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Original file line number Diff line number Diff line change
Expand Up @@ -65,6 +65,10 @@ struct rcu_ctrlblk {
long cur; /* Current batch number. */
long completed; /* Number of the last completed batch */
int next_pending; /* Is the next batch already waiting? */

spinlock_t lock ____cacheline_internodealigned_in_smp;
cpumask_t cpumask; /* CPUs that need to switch in order */
/* for current batch to proceed. */
} ____cacheline_internodealigned_in_smp;

/* Is batch a before batch b ? */
Expand Down
82 changes: 38 additions & 44 deletions kernel/rcupdate.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -49,22 +49,18 @@
#include <linux/cpu.h>

/* Definition for rcupdate control block. */
struct rcu_ctrlblk rcu_ctrlblk =
{ .cur = -300, .completed = -300 };
struct rcu_ctrlblk rcu_bh_ctrlblk =
{ .cur = -300, .completed = -300 };

/* Bookkeeping of the progress of the grace period */
struct rcu_state {
spinlock_t lock; /* Guard this struct and writes to rcu_ctrlblk */
cpumask_t cpumask; /* CPUs that need to switch in order */
/* for current batch to proceed. */
struct rcu_ctrlblk rcu_ctrlblk = {
.cur = -300,
.completed = -300,
.lock = SPIN_LOCK_UNLOCKED,
.cpumask = CPU_MASK_NONE,
};
struct rcu_ctrlblk rcu_bh_ctrlblk = {
.cur = -300,
.completed = -300,
.lock = SPIN_LOCK_UNLOCKED,
.cpumask = CPU_MASK_NONE,
};

static struct rcu_state rcu_state ____cacheline_internodealigned_in_smp =
{.lock = SPIN_LOCK_UNLOCKED, .cpumask = CPU_MASK_NONE };
static struct rcu_state rcu_bh_state ____cacheline_internodealigned_in_smp =
{.lock = SPIN_LOCK_UNLOCKED, .cpumask = CPU_MASK_NONE };

DEFINE_PER_CPU(struct rcu_data, rcu_data) = { 0L };
DEFINE_PER_CPU(struct rcu_data, rcu_bh_data) = { 0L };
Expand Down Expand Up @@ -220,23 +216,23 @@ static void rcu_do_batch(struct rcu_data *rdp)
* This is done by rcu_start_batch. The start is not broadcasted to
* all cpus, they must pick this up by comparing rcp->cur with
* rdp->quiescbatch. All cpus are recorded in the
* rcu_state.cpumask bitmap.
* rcu_ctrlblk.cpumask bitmap.
* - All cpus must go through a quiescent state.
* Since the start of the grace period is not broadcasted, at least two
* calls to rcu_check_quiescent_state are required:
* The first call just notices that a new grace period is running. The
* following calls check if there was a quiescent state since the beginning
* of the grace period. If so, it updates rcu_state.cpumask. If
* of the grace period. If so, it updates rcu_ctrlblk.cpumask. If
* the bitmap is empty, then the grace period is completed.
* rcu_check_quiescent_state calls rcu_start_batch(0) to start the next grace
* period (if necessary).
*/
/*
* Register a new batch of callbacks, and start it up if there is currently no
* active batch and the batch to be registered has not already occurred.
* Caller must hold rcu_state.lock.
* Caller must hold rcu_ctrlblk.lock.
*/
static void rcu_start_batch(struct rcu_ctrlblk *rcp, struct rcu_state *rsp)
static void rcu_start_batch(struct rcu_ctrlblk *rcp)
{
if (rcp->next_pending &&
rcp->completed == rcp->cur) {
Expand All @@ -251,11 +247,11 @@ static void rcu_start_batch(struct rcu_ctrlblk *rcp, struct rcu_state *rsp)
/*
* Accessing nohz_cpu_mask before incrementing rcp->cur needs a
* Barrier Otherwise it can cause tickless idle CPUs to be
* included in rsp->cpumask, which will extend graceperiods
* included in rcp->cpumask, which will extend graceperiods
* unnecessarily.
*/
smp_mb();
cpus_andnot(rsp->cpumask, cpu_online_map, nohz_cpu_mask);
cpus_andnot(rcp->cpumask, cpu_online_map, nohz_cpu_mask);

}
}
Expand All @@ -265,13 +261,13 @@ static void rcu_start_batch(struct rcu_ctrlblk *rcp, struct rcu_state *rsp)
* Clear it from the cpu mask and complete the grace period if it was the last
* cpu. Start another grace period if someone has further entries pending
*/
static void cpu_quiet(int cpu, struct rcu_ctrlblk *rcp, struct rcu_state *rsp)
static void cpu_quiet(int cpu, struct rcu_ctrlblk *rcp)
{
cpu_clear(cpu, rsp->cpumask);
if (cpus_empty(rsp->cpumask)) {
cpu_clear(cpu, rcp->cpumask);
if (cpus_empty(rcp->cpumask)) {
/* batch completed ! */
rcp->completed = rcp->cur;
rcu_start_batch(rcp, rsp);
rcu_start_batch(rcp);
}
}

Expand All @@ -281,7 +277,7 @@ static void cpu_quiet(int cpu, struct rcu_ctrlblk *rcp, struct rcu_state *rsp)
* quiescent cycle, then indicate that it has done so.
*/
static void rcu_check_quiescent_state(struct rcu_ctrlblk *rcp,
struct rcu_state *rsp, struct rcu_data *rdp)
struct rcu_data *rdp)
{
if (rdp->quiescbatch != rcp->cur) {
/* start new grace period: */
Expand All @@ -306,15 +302,15 @@ static void rcu_check_quiescent_state(struct rcu_ctrlblk *rcp,
return;
rdp->qs_pending = 0;

spin_lock(&rsp->lock);
spin_lock(&rcp->lock);
/*
* rdp->quiescbatch/rcp->cur and the cpu bitmap can come out of sync
* during cpu startup. Ignore the quiescent state.
*/
if (likely(rdp->quiescbatch == rcp->cur))
cpu_quiet(rdp->cpu, rcp, rsp);
cpu_quiet(rdp->cpu, rcp);

spin_unlock(&rsp->lock);
spin_unlock(&rcp->lock);
}


Expand All @@ -335,16 +331,16 @@ static void rcu_move_batch(struct rcu_data *this_rdp, struct rcu_head *list,
}

static void __rcu_offline_cpu(struct rcu_data *this_rdp,
struct rcu_ctrlblk *rcp, struct rcu_state *rsp, struct rcu_data *rdp)
struct rcu_ctrlblk *rcp, struct rcu_data *rdp)
{
/* if the cpu going offline owns the grace period
* we can block indefinitely waiting for it, so flush
* it here
*/
spin_lock_bh(&rsp->lock);
spin_lock_bh(&rcp->lock);
if (rcp->cur != rcp->completed)
cpu_quiet(rdp->cpu, rcp, rsp);
spin_unlock_bh(&rsp->lock);
cpu_quiet(rdp->cpu, rcp);
spin_unlock_bh(&rcp->lock);
rcu_move_batch(this_rdp, rdp->curlist, rdp->curtail);
rcu_move_batch(this_rdp, rdp->nxtlist, rdp->nxttail);

Expand All @@ -354,9 +350,9 @@ static void rcu_offline_cpu(int cpu)
struct rcu_data *this_rdp = &get_cpu_var(rcu_data);
struct rcu_data *this_bh_rdp = &get_cpu_var(rcu_bh_data);

__rcu_offline_cpu(this_rdp, &rcu_ctrlblk, &rcu_state,
__rcu_offline_cpu(this_rdp, &rcu_ctrlblk,
&per_cpu(rcu_data, cpu));
__rcu_offline_cpu(this_bh_rdp, &rcu_bh_ctrlblk, &rcu_bh_state,
__rcu_offline_cpu(this_bh_rdp, &rcu_bh_ctrlblk,
&per_cpu(rcu_bh_data, cpu));
put_cpu_var(rcu_data);
put_cpu_var(rcu_bh_data);
Expand All @@ -375,7 +371,7 @@ static void rcu_offline_cpu(int cpu)
* This does the RCU processing work from tasklet context.
*/
static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp,
struct rcu_state *rsp, struct rcu_data *rdp)
struct rcu_data *rdp)
{
if (rdp->curlist && !rcu_batch_before(rcp->completed, rdp->batch)) {
*rdp->donetail = rdp->curlist;
Expand Down Expand Up @@ -405,25 +401,23 @@ static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp,

if (!rcp->next_pending) {
/* and start it/schedule start if it's a new batch */
spin_lock(&rsp->lock);
spin_lock(&rcp->lock);
rcp->next_pending = 1;
rcu_start_batch(rcp, rsp);
spin_unlock(&rsp->lock);
rcu_start_batch(rcp);
spin_unlock(&rcp->lock);
}
} else {
local_irq_enable();
}
rcu_check_quiescent_state(rcp, rsp, rdp);
rcu_check_quiescent_state(rcp, rdp);
if (rdp->donelist)
rcu_do_batch(rdp);
}

static void rcu_process_callbacks(unsigned long unused)
{
__rcu_process_callbacks(&rcu_ctrlblk, &rcu_state,
&__get_cpu_var(rcu_data));
__rcu_process_callbacks(&rcu_bh_ctrlblk, &rcu_bh_state,
&__get_cpu_var(rcu_bh_data));
__rcu_process_callbacks(&rcu_ctrlblk, &__get_cpu_var(rcu_data));
__rcu_process_callbacks(&rcu_bh_ctrlblk, &__get_cpu_var(rcu_bh_data));
}

static int __rcu_pending(struct rcu_ctrlblk *rcp, struct rcu_data *rdp)
Expand Down

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