Re: Real-Time Preemption and RCU
From: Paul E. McKenney (paulmck_at_us.ibm.com)
Date: 03/19/05
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- In reply to: Paul E. McKenney: "Re: Real-Time Preemption and RCU"
- Next in thread: Ingo Molnar: "Re: Real-Time Preemption and RCU"
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Date: Fri, 18 Mar 2005 16:48:06 -0800 To: Ingo Molnar <mingo@elte.hu>
On Fri, Mar 18, 2005 at 02:22:30PM -0800, Paul E. McKenney wrote:
> On Fri, Mar 18, 2005 at 12:35:17PM -0800, Paul E. McKenney wrote:
> > Compiles, probably dies horribly. "diff" didn't do such a good job
> > on this one, so attaching the raw rcupdate.[hc] files as well.
>
> My prediction was all too accurate. ;-)
>
> The attached patch at least boots on a 1-CPU x86 box. I added some
> interrupt disabling that is a bad idea in real-time preempt kernels,
> but necessary for stock kernels to even have a ghost of a chance.
>
> Again, the diff is quite confusing to read (for me, anyway!), so attached
> the rcupdate.[hc] files.
>
> Assuming this patch survives the LTP run (hah!!!), next step is a small
> SMP system.
It did survive the UP LTP run, here is an updated patch with a fix needed
for SMP. Having trouble with test system (independent of this patch),
hopefully will get more testing in over the weekend.
Thanx, Paul
Signed-off-by: <paulmck@us.ibm.com>
diff -urpN -X ../dontdiff linux-2.5/include/linux/rcupdate.h linux-2.5-rtRCU/include/linux/rcupdate.h
--- linux-2.5/include/linux/rcupdate.h Wed Mar 9 12:37:06 2005
+++ linux-2.5-rtRCU/include/linux/rcupdate.h Fri Mar 18 11:37:02 2005
@@ -58,169 +58,11 @@ struct rcu_head {
(ptr)->next = NULL; (ptr)->func = NULL; \
} while (0)
-
-
-/* Global control variables for rcupdate callback mechanism. */
-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? */
-} ____cacheline_maxaligned_in_smp;
-
-/* Is batch a before batch b ? */
-static inline int rcu_batch_before(long a, long b)
-{
- return (a - b) < 0;
-}
-
-/* Is batch a after batch b ? */
-static inline int rcu_batch_after(long a, long b)
-{
- return (a - b) > 0;
-}
-
-/*
- * Per-CPU data for Read-Copy UPdate.
- * nxtlist - new callbacks are added here
- * curlist - current batch for which quiescent cycle started if any
- */
-struct rcu_data {
- /* 1) quiescent state handling : */
- long quiescbatch; /* Batch # for grace period */
- int passed_quiesc; /* User-mode/idle loop etc. */
- int qs_pending; /* core waits for quiesc state */
-
- /* 2) batch handling */
- long batch; /* Batch # for current RCU batch */
- struct rcu_head *nxtlist;
- struct rcu_head **nxttail;
- struct rcu_head *curlist;
- struct rcu_head **curtail;
- struct rcu_head *donelist;
- struct rcu_head **donetail;
- int cpu;
-};
-
-DECLARE_PER_CPU(struct rcu_data, rcu_data);
-DECLARE_PER_CPU(struct rcu_data, rcu_bh_data);
-extern struct rcu_ctrlblk rcu_ctrlblk;
-extern struct rcu_ctrlblk rcu_bh_ctrlblk;
-
-/*
- * Increment the quiescent state counter.
- * The counter is a bit degenerated: We do not need to know
- * how many quiescent states passed, just if there was at least
- * one since the start of the grace period. Thus just a flag.
- */
-static inline void rcu_qsctr_inc(int cpu)
-{
- struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
- rdp->passed_quiesc = 1;
-}
-static inline void rcu_bh_qsctr_inc(int cpu)
-{
- struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu);
- rdp->passed_quiesc = 1;
-}
-
-static inline int __rcu_pending(struct rcu_ctrlblk *rcp,
- struct rcu_data *rdp)
-{
- /* This cpu has pending rcu entries and the grace period
- * for them has completed.
- */
- if (rdp->curlist && !rcu_batch_before(rcp->completed, rdp->batch))
- return 1;
-
- /* This cpu has no pending entries, but there are new entries */
- if (!rdp->curlist && rdp->nxtlist)
- return 1;
-
- /* This cpu has finished callbacks to invoke */
- if (rdp->donelist)
- return 1;
-
- /* The rcu core waits for a quiescent state from the cpu */
- if (rdp->quiescbatch != rcp->cur || rdp->qs_pending)
- return 1;
-
- /* nothing to do */
- return 0;
-}
-
-static inline int rcu_pending(int cpu)
-{
- return __rcu_pending(&rcu_ctrlblk, &per_cpu(rcu_data, cpu)) ||
- __rcu_pending(&rcu_bh_ctrlblk, &per_cpu(rcu_bh_data, cpu));
-}
-
-/**
- * rcu_read_lock - mark the beginning of an RCU read-side critical section.
- *
- * When synchronize_kernel() is invoked on one CPU while other CPUs
- * are within RCU read-side critical sections, then the
- * synchronize_kernel() is guaranteed to block until after all the other
- * CPUs exit their critical sections. Similarly, if call_rcu() is invoked
- * on one CPU while other CPUs are within RCU read-side critical
- * sections, invocation of the corresponding RCU callback is deferred
- * until after the all the other CPUs exit their critical sections.
- *
- * Note, however, that RCU callbacks are permitted to run concurrently
- * with RCU read-side critical sections. One way that this can happen
- * is via the following sequence of events: (1) CPU 0 enters an RCU
- * read-side critical section, (2) CPU 1 invokes call_rcu() to register
- * an RCU callback, (3) CPU 0 exits the RCU read-side critical section,
- * (4) CPU 2 enters a RCU read-side critical section, (5) the RCU
- * callback is invoked. This is legal, because the RCU read-side critical
- * section that was running concurrently with the call_rcu() (and which
- * therefore might be referencing something that the corresponding RCU
- * callback would free up) has completed before the corresponding
- * RCU callback is invoked.
- *
- * RCU read-side critical sections may be nested. Any deferred actions
- * will be deferred until the outermost RCU read-side critical section
- * completes.
- *
- * It is illegal to block while in an RCU read-side critical section.
- */
-#define rcu_read_lock() preempt_disable()
-
-/**
- * rcu_read_unlock - marks the end of an RCU read-side critical section.
- *
- * See rcu_read_lock() for more information.
- */
-#define rcu_read_unlock() preempt_enable()
-
-/*
- * So where is rcu_write_lock()? It does not exist, as there is no
- * way for writers to lock out RCU readers. This is a feature, not
- * a bug -- this property is what provides RCU's performance benefits.
- * Of course, writers must coordinate with each other. The normal
- * spinlock primitives work well for this, but any other technique may be
- * used as well. RCU does not care how the writers keep out of each
- * others' way, as long as they do so.
- */
-
-/**
- * rcu_read_lock_bh - mark the beginning of a softirq-only RCU critical section
- *
- * This is equivalent of rcu_read_lock(), but to be used when updates
- * are being done using call_rcu_bh(). Since call_rcu_bh() callbacks
- * consider completion of a softirq handler to be a quiescent state,
- * a process in RCU read-side critical section must be protected by
- * disabling softirqs. Read-side critical sections in interrupt context
- * can use just rcu_read_lock().
- *
- */
-#define rcu_read_lock_bh() local_bh_disable()
-
-/*
- * rcu_read_unlock_bh - marks the end of a softirq-only RCU critical section
- *
- * See rcu_read_lock_bh() for more information.
- */
-#define rcu_read_unlock_bh() local_bh_enable()
+#define rcu_read_lock_bh() rcu_read_lock()
+#define rcu_read_unlock_bh() rcu_read_unlock()
+#define call_rcu_bh(head, func) call_rcu(head, func)
+#define rcu_bh_qsctr_inc(cpu)
+#define rcu_qsctr_inc(cpu)
/**
* rcu_dereference - fetch an RCU-protected pointer in an
@@ -257,15 +99,15 @@ static inline int rcu_pending(int cpu)
})
extern void rcu_init(void);
-extern void rcu_check_callbacks(int cpu, int user);
-extern void rcu_restart_cpu(int cpu);
/* Exported interfaces */
extern void FASTCALL(call_rcu(struct rcu_head *head,
void (*func)(struct rcu_head *head)));
-extern void FASTCALL(call_rcu_bh(struct rcu_head *head,
- void (*func)(struct rcu_head *head)));
+extern void rcu_read_lock(void);
+extern void rcu_read_unlock(void);
extern void synchronize_kernel(void);
+extern int rcu_pending(int cpu);
+extern void rcu_check_callbacks(int cpu, int user);
#endif /* __KERNEL__ */
#endif /* __LINUX_RCUPDATE_H */
diff -urpN -X ../dontdiff linux-2.5/include/linux/sched.h linux-2.5-rtRCU/include/linux/sched.h
--- linux-2.5/include/linux/sched.h Wed Mar 9 12:37:07 2005
+++ linux-2.5-rtRCU/include/linux/sched.h Fri Mar 18 11:33:13 2005
@@ -707,6 +707,9 @@ struct task_struct {
struct mempolicy *mempolicy;
short il_next;
#endif
+
+ int rcu_read_lock_nesting;
+ rwlock_t *rcu_read_lock_ptr;
};
static inline pid_t process_group(struct task_struct *tsk)
diff -urpN -X ../dontdiff linux-2.5/kernel/rcupdate.c linux-2.5-rtRCU/kernel/rcupdate.c
--- linux-2.5/kernel/rcupdate.c Wed Mar 9 12:37:22 2005
+++ linux-2.5-rtRCU/kernel/rcupdate.c Fri Mar 18 15:28:28 2005
@@ -47,424 +47,173 @@
#include <linux/rcupdate.h>
#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. */
+#define GRACE_PERIODS_PER_SEC 10
+
+struct rcu_data {
+ rwlock_t lock;
+ long batch;
+ struct rcu_head *waitlist;
+ struct rcu_head **waittail;
+ struct rcu_head *donelist;
+ struct rcu_head **donetail;
+};
+struct rcu_ctrlblk {
+ long batch;
+ unsigned long last_sk;
+};
+DEFINE_PER_CPU(struct rcu_data, rcu_data) = {
+ .lock = RW_LOCK_UNLOCKED,
+ .batch = 0,
+ .waitlist = NULL,
+ .donelist = NULL
+};
+struct rcu_ctrlblk rcu_ctrlblk = {
+ .batch = 0,
};
-static struct rcu_state rcu_state ____cacheline_maxaligned_in_smp =
- {.lock = SPIN_LOCK_UNLOCKED, .cpumask = CPU_MASK_NONE };
-static struct rcu_state rcu_bh_state ____cacheline_maxaligned_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 };
-
-/* Fake initialization required by compiler */
-static DEFINE_PER_CPU(struct tasklet_struct, rcu_tasklet) = {NULL};
-static int maxbatch = 10;
-
-/**
- * call_rcu - Queue an RCU callback for invocation after a grace period.
- * @head: structure to be used for queueing the RCU updates.
- * @func: actual update function to be invoked after the grace period
- *
- * The update function will be invoked some time after a full grace
- * period elapses, in other words after all currently executing RCU
- * read-side critical sections have completed. RCU read-side critical
- * sections are delimited by rcu_read_lock() and rcu_read_unlock(),
- * and may be nested.
- */
-void fastcall call_rcu(struct rcu_head *head,
- void (*func)(struct rcu_head *rcu))
+void rcu_init(void)
{
- unsigned long flags;
+ int cpu;
struct rcu_data *rdp;
- head->func = func;
- head->next = NULL;
- local_irq_save(flags);
- rdp = &__get_cpu_var(rcu_data);
- *rdp->nxttail = head;
- rdp->nxttail = &head->next;
- local_irq_restore(flags);
+ for_each_cpu(cpu) {
+ rdp = &per_cpu(rcu_data, cpu);
+ rdp->waittail = &rdp->waitlist;
+ rdp->donetail = &rdp->donelist;
+ }
}
-/**
- * call_rcu_bh - Queue an RCU for invocation after a quicker grace period.
- * @head: structure to be used for queueing the RCU updates.
- * @func: actual update function to be invoked after the grace period
- *
- * The update function will be invoked some time after a full grace
- * period elapses, in other words after all currently executing RCU
- * read-side critical sections have completed. call_rcu_bh() assumes
- * that the read-side critical sections end on completion of a softirq
- * handler. This means that read-side critical sections in process
- * context must not be interrupted by softirqs. This interface is to be
- * used when most of the read-side critical sections are in softirq context.
- * RCU read-side critical sections are delimited by rcu_read_lock() and
- * rcu_read_unlock(), * if in interrupt context or rcu_read_lock_bh()
- * and rcu_read_unlock_bh(), if in process context. These may be nested.
- */
-void fastcall call_rcu_bh(struct rcu_head *head,
- void (*func)(struct rcu_head *rcu))
+void rcu_read_lock(void)
{
unsigned long flags;
- struct rcu_data *rdp;
- head->func = func;
- head->next = NULL;
- local_irq_save(flags);
- rdp = &__get_cpu_var(rcu_bh_data);
- *rdp->nxttail = head;
- rdp->nxttail = &head->next;
+ local_irq_save(flags); /* allow invocation from OOM handler. */
+ if (current->rcu_read_lock_nesting++ == 0) {
+ current->rcu_read_lock_ptr = &__get_cpu_var(rcu_data).lock;
+ read_lock(current->rcu_read_lock_ptr);
+ }
local_irq_restore(flags);
}
-/*
- * Invoke the completed RCU callbacks. They are expected to be in
- * a per-cpu list.
- */
-static void rcu_do_batch(struct rcu_data *rdp)
+void rcu_read_unlock(void)
{
- struct rcu_head *next, *list;
- int count = 0;
+ unsigned long flags;
- list = rdp->donelist;
- while (list) {
- next = rdp->donelist = list->next;
- list->func(list);
- list = next;
- if (++count >= maxbatch)
- break;
+ local_irq_save(flags); /* allow invocation from OOM handler. */
+ if (--current->rcu_read_lock_nesting == 0) {
+ read_unlock(current->rcu_read_lock_ptr);
}
- if (!rdp->donelist)
- rdp->donetail = &rdp->donelist;
- else
- tasklet_schedule(&per_cpu(rcu_tasklet, rdp->cpu));
+ local_irq_restore(flags);
}
-/*
- * Grace period handling:
- * The grace period handling consists out of two steps:
- * - A new grace period is started.
- * 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.
- * - 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
- * 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.
- */
-static void rcu_start_batch(struct rcu_ctrlblk *rcp, struct rcu_state *rsp,
- int next_pending)
+void _synchronize_kernel(void)
{
- if (next_pending)
- rcp->next_pending = 1;
+ int cpu;
+ unsigned long flags;
- if (rcp->next_pending &&
- rcp->completed == rcp->cur) {
- /* Can't change, since spin lock held. */
- cpus_andnot(rsp->cpumask, cpu_online_map, nohz_cpu_mask);
-
- rcp->next_pending = 0;
- /* next_pending == 0 must be visible in __rcu_process_callbacks()
- * before it can see new value of cur.
- */
- smp_wmb();
- rcp->cur++;
+ local_irq_save(flags); /* allow invocation from OOM handler. */
+ for_each_cpu(cpu) { /* _online() or _present() races with hotplug */
+ write_lock(&per_cpu(rcu_data, cpu).lock);
+ }
+ rcu_ctrlblk.batch++;
+ rcu_ctrlblk.last_sk = jiffies;
+ for_each_cpu(cpu) {
+ write_unlock(&per_cpu(rcu_data, cpu).lock);
}
+ local_irq_restore(flags);
}
-/*
- * cpu went through a quiescent state since the beginning of the grace period.
- * 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)
+void synchronize_kernel(void)
{
- cpu_clear(cpu, rsp->cpumask);
- if (cpus_empty(rsp->cpumask)) {
- /* batch completed ! */
- rcp->completed = rcp->cur;
- rcu_start_batch(rcp, rsp, 0);
- }
-}
+ long oldbatch;
-/*
- * Check if the cpu has gone through a quiescent state (say context
- * switch). If so and if it already hasn't done so in this RCU
- * 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)
-{
- if (rdp->quiescbatch != rcp->cur) {
- /* start new grace period: */
- rdp->qs_pending = 1;
- rdp->passed_quiesc = 0;
- rdp->quiescbatch = rcp->cur;
- return;
+ smp_mb();
+ oldbatch = rcu_ctrlblk.batch;
+ schedule_timeout(HZ/GRACE_PERIODS_PER_SEC);
+ if (rcu_ctrlblk.batch == oldbatch) {
+ _synchronize_kernel();
}
-
- /* Grace period already completed for this cpu?
- * qs_pending is checked instead of the actual bitmap to avoid
- * cacheline trashing.
- */
- if (!rdp->qs_pending)
- return;
-
- /*
- * Was there a quiescent state since the beginning of the grace
- * period? If no, then exit and wait for the next call.
- */
- if (!rdp->passed_quiesc)
- return;
- rdp->qs_pending = 0;
-
- spin_lock(&rsp->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);
-
- spin_unlock(&rsp->lock);
-}
-
-
-#ifdef CONFIG_HOTPLUG_CPU
-
-/* warning! helper for rcu_offline_cpu. do not use elsewhere without reviewing
- * locking requirements, the list it's pulling from has to belong to a cpu
- * which is dead and hence not processing interrupts.
- */
-static void rcu_move_batch(struct rcu_data *this_rdp, struct rcu_head *list,
- struct rcu_head **tail)
-{
- local_irq_disable();
- *this_rdp->nxttail = list;
- if (list)
- this_rdp->nxttail = tail;
- local_irq_enable();
}
-static void __rcu_offline_cpu(struct rcu_data *this_rdp,
- struct rcu_ctrlblk *rcp, struct rcu_state *rsp, struct rcu_data *rdp)
+void rcu_advance_callbacks(void)
{
- /* 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);
- if (rcp->cur != rcp->completed)
- cpu_quiet(rdp->cpu, rcp, rsp);
- spin_unlock_bh(&rsp->lock);
- rcu_move_batch(this_rdp, rdp->curlist, rdp->curtail);
- rcu_move_batch(this_rdp, rdp->nxtlist, rdp->nxttail);
+ unsigned long flags;
+ struct rcu_data *rdp;
+ local_irq_save(flags); /* allow invocation from OOM handler. */
+ rdp = &__get_cpu_var(rcu_data);
+ smp_mb(); /* prevent sampling batch # before list removal. */
+ if (rdp->batch != rcu_ctrlblk.batch) {
+ *rdp->donetail = rdp->waitlist;
+ rdp->donetail = rdp->waittail;
+ rdp->waitlist = NULL;
+ rdp->waittail = &rdp->waitlist;
+ rdp->batch = rcu_ctrlblk.batch;
+ }
+ local_irq_restore(flags);
}
-static void rcu_offline_cpu(int cpu)
+
+void call_rcu(struct rcu_head *head,
+ void (*func)(struct rcu_head *rcu))
{
- struct rcu_data *this_rdp = &get_cpu_var(rcu_data);
- struct rcu_data *this_bh_rdp = &get_cpu_var(rcu_bh_data);
+ unsigned long flags;
+ struct rcu_data *rdp;
- __rcu_offline_cpu(this_rdp, &rcu_ctrlblk, &rcu_state,
- &per_cpu(rcu_data, cpu));
- __rcu_offline_cpu(this_bh_rdp, &rcu_bh_ctrlblk, &rcu_bh_state,
- &per_cpu(rcu_bh_data, cpu));
- put_cpu_var(rcu_data);
- put_cpu_var(rcu_bh_data);
- tasklet_kill_immediate(&per_cpu(rcu_tasklet, cpu), cpu);
+ head->func = func;
+ head->next = NULL;
+ local_irq_save(flags);
+ rcu_advance_callbacks();
+ rdp = &__get_cpu_var(rcu_data);
+ *rdp->waittail = head;
+ rdp->waittail = &head->next;
+ local_irq_restore(flags);
}
-#else
-
-static void rcu_offline_cpu(int cpu)
+void rcu_process_callbacks(void)
{
-}
-
-#endif
+ unsigned long flags;
+ struct rcu_head *next, *list;
+ struct rcu_data *rdp;
-/*
- * 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)
-{
- if (rdp->curlist && !rcu_batch_before(rcp->completed, rdp->batch)) {
- *rdp->donetail = rdp->curlist;
- rdp->donetail = rdp->curtail;
- rdp->curlist = NULL;
- rdp->curtail = &rdp->curlist;
+ local_irq_save(flags);
+ rdp = &__get_cpu_var(rcu_data);
+ list = rdp->donelist;
+ if (list == NULL) {
+ local_irq_restore(flags);
+ return;
}
-
- local_irq_disable();
- if (rdp->nxtlist && !rdp->curlist) {
- rdp->curlist = rdp->nxtlist;
- rdp->curtail = rdp->nxttail;
- rdp->nxtlist = NULL;
- rdp->nxttail = &rdp->nxtlist;
- local_irq_enable();
-
- /*
- * start the next batch of callbacks
- */
-
- /* determine batch number */
- rdp->batch = rcp->cur + 1;
- /* see the comment and corresponding wmb() in
- * the rcu_start_batch()
- */
- smp_rmb();
-
- if (!rcp->next_pending) {
- /* and start it/schedule start if it's a new batch */
- spin_lock(&rsp->lock);
- rcu_start_batch(rcp, rsp, 1);
- spin_unlock(&rsp->lock);
- }
- } else {
- local_irq_enable();
+ rdp->donelist = NULL;
+ rdp->donetail = &rdp->waitlist;
+ local_irq_restore(flags);
+ while (list) {
+ next = list->next;
+ list->func(list);
+ list = next;
}
- rcu_check_quiescent_state(rcp, rsp, 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));
}
void rcu_check_callbacks(int cpu, int user)
{
- if (user ||
- (idle_cpu(cpu) && !in_softirq() &&
- hardirq_count() <= (1 << HARDIRQ_SHIFT))) {
- rcu_qsctr_inc(cpu);
- rcu_bh_qsctr_inc(cpu);
- } else if (!in_softirq())
- rcu_bh_qsctr_inc(cpu);
- tasklet_schedule(&per_cpu(rcu_tasklet, cpu));
-}
-
-static void rcu_init_percpu_data(int cpu, struct rcu_ctrlblk *rcp,
- struct rcu_data *rdp)
-{
- memset(rdp, 0, sizeof(*rdp));
- rdp->curtail = &rdp->curlist;
- rdp->nxttail = &rdp->nxtlist;
- rdp->donetail = &rdp->donelist;
- rdp->quiescbatch = rcp->completed;
- rdp->qs_pending = 0;
- rdp->cpu = cpu;
-}
-
-static void __devinit rcu_online_cpu(int cpu)
-{
- struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
- struct rcu_data *bh_rdp = &per_cpu(rcu_bh_data, cpu);
-
- rcu_init_percpu_data(cpu, &rcu_ctrlblk, rdp);
- rcu_init_percpu_data(cpu, &rcu_bh_ctrlblk, bh_rdp);
- tasklet_init(&per_cpu(rcu_tasklet, cpu), rcu_process_callbacks, 0UL);
-}
-
-static int __devinit rcu_cpu_notify(struct notifier_block *self,
- unsigned long action, void *hcpu)
-{
- long cpu = (long)hcpu;
- switch (action) {
- case CPU_UP_PREPARE:
- rcu_online_cpu(cpu);
- break;
- case CPU_DEAD:
- rcu_offline_cpu(cpu);
- break;
- default:
- break;
+ if ((unsigned long)(jiffies - rcu_ctrlblk.last_sk) >
+ HZ/GRACE_PERIODS_PER_SEC) {
+ synchronize_kernel();
+ rcu_advance_callbacks();
+ rcu_process_callbacks();
}
- return NOTIFY_OK;
}
-static struct notifier_block __devinitdata rcu_nb = {
- .notifier_call = rcu_cpu_notify,
-};
-
-/*
- * Initializes rcu mechanism. Assumed to be called early.
- * That is before local timer(SMP) or jiffie timer (uniproc) is setup.
- * Note that rcu_qsctr and friends are implicitly
- * initialized due to the choice of ``0'' for RCU_CTR_INVALID.
- */
-void __init rcu_init(void)
+int rcu_pending(int cpu)
{
- rcu_cpu_notify(&rcu_nb, CPU_UP_PREPARE,
- (void *)(long)smp_processor_id());
- /* Register notifier for non-boot CPUs */
- register_cpu_notifier(&rcu_nb);
-}
-
-struct rcu_synchronize {
- struct rcu_head head;
- struct completion completion;
-};
-
-/* Because of FASTCALL declaration of complete, we use this wrapper */
-static void wakeme_after_rcu(struct rcu_head *head)
-{
- struct rcu_synchronize *rcu;
-
- rcu = container_of(head, struct rcu_synchronize, head);
- complete(&rcu->completion);
-}
-
-/**
- * synchronize_kernel - wait until a grace period has elapsed.
- *
- * Control will return to the caller some time after a full grace
- * period has elapsed, in other words after all currently executing RCU
- * read-side critical sections have completed. RCU read-side critical
- * sections are delimited by rcu_read_lock() and rcu_read_unlock(),
- * and may be nested.
- */
-void synchronize_kernel(void)
-{
- struct rcu_synchronize rcu;
-
- init_completion(&rcu.completion);
- /* Will wake me after RCU finished */
- call_rcu(&rcu.head, wakeme_after_rcu);
+ unsigned long flags;
+ struct rcu_data *rdp;
+ int retval;
- /* Wait for it */
- wait_for_completion(&rcu.completion);
+ local_irq_save(flags);
+ rdp = &__get_cpu_var(rcu_data);
+ retval = (rdp->waitlist || rdp->donelist);
+ local_irq_restore(flags);
+ return (retval);
}
-module_param(maxbatch, int, 0);
EXPORT_SYMBOL(call_rcu);
-EXPORT_SYMBOL(call_rcu_bh);
EXPORT_SYMBOL(synchronize_kernel);
-
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