#include <linux/vmalloc.h>
#include <linux/mm.h>
#include <linux/kasan.h>
+#include <linux/context_tracking.h>
#include "../time/tick-internal.h"
#include "tree.h"
/* Data structures. */
static DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_data, rcu_data) = {
- .dynticks_nesting = 1,
- .dynticks_nmi_nesting = DYNTICK_IRQ_NONIDLE,
- .dynticks = ATOMIC_INIT(1),
#ifdef CONFIG_RCU_NOCB_CPU
.cblist.flags = SEGCBLIST_RCU_CORE,
#endif
static void check_cb_ovld_locked(struct rcu_data *rdp, struct rcu_node *rnp);
static bool rcu_rdp_is_offloaded(struct rcu_data *rdp);
-/* rcuc/rcub/rcuop kthread realtime priority */
+/*
+ * rcuc/rcub/rcuop kthread realtime priority. The "rcuop"
+ * real-time priority(enabling/disabling) is controlled by
+ * the extra CONFIG_RCU_NOCB_CPU_CB_BOOST configuration.
+ */
static int kthread_prio = IS_ENABLED(CONFIG_RCU_BOOST) ? 1 : 0;
module_param(kthread_prio, int, 0444);
rcu_tasks_qs(current, false);
}
-/*
- * Increment the current CPU's rcu_data structure's ->dynticks field
- * with ordering. Return the new value.
- */
-static noinline noinstr unsigned long rcu_dynticks_inc(int incby)
-{
- return arch_atomic_add_return(incby, this_cpu_ptr(&rcu_data.dynticks));
-}
-
-/*
- * Record entry into an extended quiescent state. This is only to be
- * called when not already in an extended quiescent state, that is,
- * RCU is watching prior to the call to this function and is no longer
- * watching upon return.
- */
-static noinstr void rcu_dynticks_eqs_enter(void)
-{
- int seq;
-
- /*
- * CPUs seeing atomic_add_return() must see prior RCU read-side
- * critical sections, and we also must force ordering with the
- * next idle sojourn.
- */
- rcu_dynticks_task_trace_enter(); // Before ->dynticks update!
- seq = rcu_dynticks_inc(1);
- // RCU is no longer watching. Better be in extended quiescent state!
- WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && (seq & 0x1));
-}
-
-/*
- * Record exit from an extended quiescent state. This is only to be
- * called from an extended quiescent state, that is, RCU is not watching
- * prior to the call to this function and is watching upon return.
- */
-static noinstr void rcu_dynticks_eqs_exit(void)
-{
- int seq;
-
- /*
- * CPUs seeing atomic_add_return() must see prior idle sojourns,
- * and we also must force ordering with the next RCU read-side
- * critical section.
- */
- seq = rcu_dynticks_inc(1);
- // RCU is now watching. Better not be in an extended quiescent state!
- rcu_dynticks_task_trace_exit(); // After ->dynticks update!
- WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !(seq & 0x1));
-}
-
/*
* Reset the current CPU's ->dynticks counter to indicate that the
* newly onlined CPU is no longer in an extended quiescent state.
*/
static void rcu_dynticks_eqs_online(void)
{
- struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
-
- if (atomic_read(&rdp->dynticks) & 0x1)
+ if (ct_dynticks() & RCU_DYNTICKS_IDX)
return;
- rcu_dynticks_inc(1);
-}
-
-/*
- * Is the current CPU in an extended quiescent state?
- *
- * No ordering, as we are sampling CPU-local information.
- */
-static __always_inline bool rcu_dynticks_curr_cpu_in_eqs(void)
-{
- return !(arch_atomic_read(this_cpu_ptr(&rcu_data.dynticks)) & 0x1);
+ ct_state_inc(RCU_DYNTICKS_IDX);
}
/*
* Snapshot the ->dynticks counter with full ordering so as to allow
* stable comparison of this counter with past and future snapshots.
*/
-static int rcu_dynticks_snap(struct rcu_data *rdp)
+static int rcu_dynticks_snap(int cpu)
{
smp_mb(); // Fundamental RCU ordering guarantee.
- return atomic_read_acquire(&rdp->dynticks);
+ return ct_dynticks_cpu_acquire(cpu);
}
/*
*/
static bool rcu_dynticks_in_eqs(int snap)
{
- return !(snap & 0x1);
+ return !(snap & RCU_DYNTICKS_IDX);
}
/* Return true if the specified CPU is currently idle from an RCU viewpoint. */
bool rcu_is_idle_cpu(int cpu)
{
- struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
-
- return rcu_dynticks_in_eqs(rcu_dynticks_snap(rdp));
+ return rcu_dynticks_in_eqs(rcu_dynticks_snap(cpu));
}
/*
*/
static bool rcu_dynticks_in_eqs_since(struct rcu_data *rdp, int snap)
{
- return snap != rcu_dynticks_snap(rdp);
+ return snap != rcu_dynticks_snap(rdp->cpu);
}
/*
*/
bool rcu_dynticks_zero_in_eqs(int cpu, int *vp)
{
- struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
int snap;
// If not quiescent, force back to earlier extended quiescent state.
- snap = atomic_read(&rdp->dynticks) & ~0x1;
-
+ snap = ct_dynticks_cpu(cpu) & ~RCU_DYNTICKS_IDX;
smp_rmb(); // Order ->dynticks and *vp reads.
if (READ_ONCE(*vp))
return false; // Non-zero, so report failure;
smp_rmb(); // Order *vp read and ->dynticks re-read.
// If still in the same extended quiescent state, we are good!
- return snap == atomic_read(&rdp->dynticks);
+ return snap == ct_dynticks_cpu(cpu);
}
/*
int seq;
raw_cpu_write(rcu_data.rcu_need_heavy_qs, false);
- seq = rcu_dynticks_inc(2);
+ seq = ct_state_inc(2 * RCU_DYNTICKS_IDX);
/* It is illegal to call this from idle state. */
- WARN_ON_ONCE(!(seq & 0x1));
+ WARN_ON_ONCE(!(seq & RCU_DYNTICKS_IDX));
rcu_preempt_deferred_qs(current);
}
EXPORT_SYMBOL_GPL(rcu_momentary_dyntick_idle);
lockdep_assert_irqs_disabled();
/* Check for counter underflows */
- RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nesting) < 0,
+ RCU_LOCKDEP_WARN(ct_dynticks_nesting() < 0,
"RCU dynticks_nesting counter underflow!");
- RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nmi_nesting) <= 0,
+ RCU_LOCKDEP_WARN(ct_dynticks_nmi_nesting() <= 0,
"RCU dynticks_nmi_nesting counter underflow/zero!");
/* Are we at first interrupt nesting level? */
- nesting = __this_cpu_read(rcu_data.dynticks_nmi_nesting);
+ nesting = ct_dynticks_nmi_nesting();
if (nesting > 1)
return false;
WARN_ON_ONCE(!nesting && !is_idle_task(current));
/* Does CPU appear to be idle from an RCU standpoint? */
- return __this_cpu_read(rcu_data.dynticks_nesting) == 0;
+ return ct_dynticks_nesting() == 0;
}
#define DEFAULT_RCU_BLIMIT (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD) ? 1000 : 10)
}
EXPORT_SYMBOL_GPL(rcutorture_get_gp_data);
-/*
- * Enter an RCU extended quiescent state, which can be either the
- * idle loop or adaptive-tickless usermode execution.
- *
- * We crowbar the ->dynticks_nmi_nesting field to zero to allow for
- * the possibility of usermode upcalls having messed up our count
- * of interrupt nesting level during the prior busy period.
- */
-static noinstr void rcu_eqs_enter(bool user)
-{
- struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
-
- WARN_ON_ONCE(rdp->dynticks_nmi_nesting != DYNTICK_IRQ_NONIDLE);
- WRITE_ONCE(rdp->dynticks_nmi_nesting, 0);
- WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
- rdp->dynticks_nesting == 0);
- if (rdp->dynticks_nesting != 1) {
- // RCU will still be watching, so just do accounting and leave.
- rdp->dynticks_nesting--;
- return;
- }
-
- lockdep_assert_irqs_disabled();
- instrumentation_begin();
- trace_rcu_dyntick(TPS("Start"), rdp->dynticks_nesting, 0, atomic_read(&rdp->dynticks));
- WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current));
- rcu_preempt_deferred_qs(current);
-
- // instrumentation for the noinstr rcu_dynticks_eqs_enter()
- instrument_atomic_write(&rdp->dynticks, sizeof(rdp->dynticks));
-
- instrumentation_end();
- WRITE_ONCE(rdp->dynticks_nesting, 0); /* Avoid irq-access tearing. */
- // RCU is watching here ...
- rcu_dynticks_eqs_enter();
- // ... but is no longer watching here.
- rcu_dynticks_task_enter();
-}
-
-/**
- * rcu_idle_enter - inform RCU that current CPU is entering idle
- *
- * Enter idle mode, in other words, -leave- the mode in which RCU
- * read-side critical sections can occur. (Though RCU read-side
- * critical sections can occur in irq handlers in idle, a possibility
- * handled by irq_enter() and irq_exit().)
- *
- * If you add or remove a call to rcu_idle_enter(), be sure to test with
- * CONFIG_RCU_EQS_DEBUG=y.
- */
-void rcu_idle_enter(void)
-{
- lockdep_assert_irqs_disabled();
- rcu_eqs_enter(false);
-}
-EXPORT_SYMBOL_GPL(rcu_idle_enter);
-
-#ifdef CONFIG_NO_HZ_FULL
-
-#if !defined(CONFIG_GENERIC_ENTRY) || !defined(CONFIG_KVM_XFER_TO_GUEST_WORK)
+#if defined(CONFIG_NO_HZ_FULL) && (!defined(CONFIG_GENERIC_ENTRY) || !defined(CONFIG_KVM_XFER_TO_GUEST_WORK))
/*
* An empty function that will trigger a reschedule on
* IRQ tail once IRQs get re-enabled on userspace/guest resume.
* last resort is to fire a local irq_work that will trigger a reschedule once IRQs
* get re-enabled again.
*/
-noinstr static void rcu_irq_work_resched(void)
+noinstr void rcu_irq_work_resched(void)
{
struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
}
instrumentation_end();
}
-
-#else
-static inline void rcu_irq_work_resched(void) { }
-#endif
-
-/**
- * rcu_user_enter - inform RCU that we are resuming userspace.
- *
- * Enter RCU idle mode right before resuming userspace. No use of RCU
- * is permitted between this call and rcu_user_exit(). This way the
- * CPU doesn't need to maintain the tick for RCU maintenance purposes
- * when the CPU runs in userspace.
- *
- * If you add or remove a call to rcu_user_enter(), be sure to test with
- * CONFIG_RCU_EQS_DEBUG=y.
- */
-noinstr void rcu_user_enter(void)
-{
- lockdep_assert_irqs_disabled();
-
- /*
- * Other than generic entry implementation, we may be past the last
- * rescheduling opportunity in the entry code. Trigger a self IPI
- * that will fire and reschedule once we resume in user/guest mode.
- */
- rcu_irq_work_resched();
- rcu_eqs_enter(true);
-}
-
-#endif /* CONFIG_NO_HZ_FULL */
-
-/**
- * rcu_nmi_exit - inform RCU of exit from NMI context
- *
- * If we are returning from the outermost NMI handler that interrupted an
- * RCU-idle period, update rdp->dynticks and rdp->dynticks_nmi_nesting
- * to let the RCU grace-period handling know that the CPU is back to
- * being RCU-idle.
- *
- * If you add or remove a call to rcu_nmi_exit(), be sure to test
- * with CONFIG_RCU_EQS_DEBUG=y.
- */
-noinstr void rcu_nmi_exit(void)
-{
- struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
-
- instrumentation_begin();
- /*
- * Check for ->dynticks_nmi_nesting underflow and bad ->dynticks.
- * (We are exiting an NMI handler, so RCU better be paying attention
- * to us!)
- */
- WARN_ON_ONCE(rdp->dynticks_nmi_nesting <= 0);
- WARN_ON_ONCE(rcu_dynticks_curr_cpu_in_eqs());
-
- /*
- * If the nesting level is not 1, the CPU wasn't RCU-idle, so
- * leave it in non-RCU-idle state.
- */
- if (rdp->dynticks_nmi_nesting != 1) {
- trace_rcu_dyntick(TPS("--="), rdp->dynticks_nmi_nesting, rdp->dynticks_nmi_nesting - 2,
- atomic_read(&rdp->dynticks));
- WRITE_ONCE(rdp->dynticks_nmi_nesting, /* No store tearing. */
- rdp->dynticks_nmi_nesting - 2);
- instrumentation_end();
- return;
- }
-
- /* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */
- trace_rcu_dyntick(TPS("Startirq"), rdp->dynticks_nmi_nesting, 0, atomic_read(&rdp->dynticks));
- WRITE_ONCE(rdp->dynticks_nmi_nesting, 0); /* Avoid store tearing. */
-
- // instrumentation for the noinstr rcu_dynticks_eqs_enter()
- instrument_atomic_write(&rdp->dynticks, sizeof(rdp->dynticks));
- instrumentation_end();
-
- // RCU is watching here ...
- rcu_dynticks_eqs_enter();
- // ... but is no longer watching here.
-
- if (!in_nmi())
- rcu_dynticks_task_enter();
-}
-
-/**
- * rcu_irq_exit - inform RCU that current CPU is exiting irq towards idle
- *
- * Exit from an interrupt handler, which might possibly result in entering
- * idle mode, in other words, leaving the mode in which read-side critical
- * sections can occur. The caller must have disabled interrupts.
- *
- * This code assumes that the idle loop never does anything that might
- * result in unbalanced calls to irq_enter() and irq_exit(). If your
- * architecture's idle loop violates this assumption, RCU will give you what
- * you deserve, good and hard. But very infrequently and irreproducibly.
- *
- * Use things like work queues to work around this limitation.
- *
- * You have been warned.
- *
- * If you add or remove a call to rcu_irq_exit(), be sure to test with
- * CONFIG_RCU_EQS_DEBUG=y.
- */
-void noinstr rcu_irq_exit(void)
-{
- lockdep_assert_irqs_disabled();
- rcu_nmi_exit();
-}
+#endif /* #if defined(CONFIG_NO_HZ_FULL) && (!defined(CONFIG_GENERIC_ENTRY) || !defined(CONFIG_KVM_XFER_TO_GUEST_WORK)) */
#ifdef CONFIG_PROVE_RCU
/**
{
lockdep_assert_irqs_disabled();
- RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nesting) <= 0,
+ RCU_LOCKDEP_WARN(ct_dynticks_nesting() <= 0,
"RCU dynticks_nesting counter underflow/zero!");
- RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nmi_nesting) !=
+ RCU_LOCKDEP_WARN(ct_dynticks_nmi_nesting() !=
DYNTICK_IRQ_NONIDLE,
"Bad RCU dynticks_nmi_nesting counter\n");
RCU_LOCKDEP_WARN(rcu_dynticks_curr_cpu_in_eqs(),
}
#endif /* #ifdef CONFIG_PROVE_RCU */
-/*
- * Wrapper for rcu_irq_exit() where interrupts are enabled.
- *
- * If you add or remove a call to rcu_irq_exit_irqson(), be sure to test
- * with CONFIG_RCU_EQS_DEBUG=y.
- */
-void rcu_irq_exit_irqson(void)
-{
- unsigned long flags;
-
- local_irq_save(flags);
- rcu_irq_exit();
- local_irq_restore(flags);
-}
-
-/*
- * Exit an RCU extended quiescent state, which can be either the
- * idle loop or adaptive-tickless usermode execution.
- *
- * We crowbar the ->dynticks_nmi_nesting field to DYNTICK_IRQ_NONIDLE to
- * allow for the possibility of usermode upcalls messing up our count of
- * interrupt nesting level during the busy period that is just now starting.
- */
-static void noinstr rcu_eqs_exit(bool user)
-{
- struct rcu_data *rdp;
- long oldval;
-
- lockdep_assert_irqs_disabled();
- rdp = this_cpu_ptr(&rcu_data);
- oldval = rdp->dynticks_nesting;
- WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && oldval < 0);
- if (oldval) {
- // RCU was already watching, so just do accounting and leave.
- rdp->dynticks_nesting++;
- return;
- }
- rcu_dynticks_task_exit();
- // RCU is not watching here ...
- rcu_dynticks_eqs_exit();
- // ... but is watching here.
- instrumentation_begin();
-
- // instrumentation for the noinstr rcu_dynticks_eqs_exit()
- instrument_atomic_write(&rdp->dynticks, sizeof(rdp->dynticks));
-
- trace_rcu_dyntick(TPS("End"), rdp->dynticks_nesting, 1, atomic_read(&rdp->dynticks));
- WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current));
- WRITE_ONCE(rdp->dynticks_nesting, 1);
- WARN_ON_ONCE(rdp->dynticks_nmi_nesting);
- WRITE_ONCE(rdp->dynticks_nmi_nesting, DYNTICK_IRQ_NONIDLE);
- instrumentation_end();
-}
-
-/**
- * rcu_idle_exit - inform RCU that current CPU is leaving idle
- *
- * Exit idle mode, in other words, -enter- the mode in which RCU
- * read-side critical sections can occur.
- *
- * If you add or remove a call to rcu_idle_exit(), be sure to test with
- * CONFIG_RCU_EQS_DEBUG=y.
- */
-void rcu_idle_exit(void)
-{
- unsigned long flags;
-
- local_irq_save(flags);
- rcu_eqs_exit(false);
- local_irq_restore(flags);
-}
-EXPORT_SYMBOL_GPL(rcu_idle_exit);
-
#ifdef CONFIG_NO_HZ_FULL
-/**
- * rcu_user_exit - inform RCU that we are exiting userspace.
- *
- * Exit RCU idle mode while entering the kernel because it can
- * run a RCU read side critical section anytime.
- *
- * If you add or remove a call to rcu_user_exit(), be sure to test with
- * CONFIG_RCU_EQS_DEBUG=y.
- */
-void noinstr rcu_user_exit(void)
-{
- rcu_eqs_exit(true);
-}
-
/**
* __rcu_irq_enter_check_tick - Enable scheduler tick on CPU if RCU needs it.
*
}
#endif /* CONFIG_NO_HZ_FULL */
-/**
- * rcu_nmi_enter - inform RCU of entry to NMI context
- *
- * If the CPU was idle from RCU's viewpoint, update rdp->dynticks and
- * rdp->dynticks_nmi_nesting to let the RCU grace-period handling know
- * that the CPU is active. This implementation permits nested NMIs, as
- * long as the nesting level does not overflow an int. (You will probably
- * run out of stack space first.)
- *
- * If you add or remove a call to rcu_nmi_enter(), be sure to test
- * with CONFIG_RCU_EQS_DEBUG=y.
- */
-noinstr void rcu_nmi_enter(void)
-{
- long incby = 2;
- struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
-
- /* Complain about underflow. */
- WARN_ON_ONCE(rdp->dynticks_nmi_nesting < 0);
-
- /*
- * If idle from RCU viewpoint, atomically increment ->dynticks
- * to mark non-idle and increment ->dynticks_nmi_nesting by one.
- * Otherwise, increment ->dynticks_nmi_nesting by two. This means
- * if ->dynticks_nmi_nesting is equal to one, we are guaranteed
- * to be in the outermost NMI handler that interrupted an RCU-idle
- * period (observation due to Andy Lutomirski).
- */
- if (rcu_dynticks_curr_cpu_in_eqs()) {
-
- if (!in_nmi())
- rcu_dynticks_task_exit();
-
- // RCU is not watching here ...
- rcu_dynticks_eqs_exit();
- // ... but is watching here.
-
- instrumentation_begin();
- // instrumentation for the noinstr rcu_dynticks_curr_cpu_in_eqs()
- instrument_atomic_read(&rdp->dynticks, sizeof(rdp->dynticks));
- // instrumentation for the noinstr rcu_dynticks_eqs_exit()
- instrument_atomic_write(&rdp->dynticks, sizeof(rdp->dynticks));
-
- incby = 1;
- } else if (!in_nmi()) {
- instrumentation_begin();
- rcu_irq_enter_check_tick();
- } else {
- instrumentation_begin();
- }
-
- trace_rcu_dyntick(incby == 1 ? TPS("Endirq") : TPS("++="),
- rdp->dynticks_nmi_nesting,
- rdp->dynticks_nmi_nesting + incby, atomic_read(&rdp->dynticks));
- instrumentation_end();
- WRITE_ONCE(rdp->dynticks_nmi_nesting, /* Prevent store tearing. */
- rdp->dynticks_nmi_nesting + incby);
- barrier();
-}
-
-/**
- * rcu_irq_enter - inform RCU that current CPU is entering irq away from idle
- *
- * Enter an interrupt handler, which might possibly result in exiting
- * idle mode, in other words, entering the mode in which read-side critical
- * sections can occur. The caller must have disabled interrupts.
- *
- * Note that the Linux kernel is fully capable of entering an interrupt
- * handler that it never exits, for example when doing upcalls to user mode!
- * This code assumes that the idle loop never does upcalls to user mode.
- * If your architecture's idle loop does do upcalls to user mode (or does
- * anything else that results in unbalanced calls to the irq_enter() and
- * irq_exit() functions), RCU will give you what you deserve, good and hard.
- * But very infrequently and irreproducibly.
- *
- * Use things like work queues to work around this limitation.
- *
- * You have been warned.
- *
- * If you add or remove a call to rcu_irq_enter(), be sure to test with
- * CONFIG_RCU_EQS_DEBUG=y.
- */
-noinstr void rcu_irq_enter(void)
-{
- lockdep_assert_irqs_disabled();
- rcu_nmi_enter();
-}
-
-/*
- * Wrapper for rcu_irq_enter() where interrupts are enabled.
- *
- * If you add or remove a call to rcu_irq_enter_irqson(), be sure to test
- * with CONFIG_RCU_EQS_DEBUG=y.
- */
-void rcu_irq_enter_irqson(void)
-{
- unsigned long flags;
-
- local_irq_save(flags);
- rcu_irq_enter();
- local_irq_restore(flags);
-}
-
/*
* Check to see if any future non-offloaded RCU-related work will need
* to be done by the current CPU, even if none need be done immediately,
*/
static int dyntick_save_progress_counter(struct rcu_data *rdp)
{
- rdp->dynticks_snap = rcu_dynticks_snap(rdp);
+ rdp->dynticks_snap = rcu_dynticks_snap(rdp->cpu);
if (rcu_dynticks_in_eqs(rdp->dynticks_snap)) {
trace_rcu_fqs(rcu_state.name, rdp->gp_seq, rdp->cpu, TPS("dti"));
rcu_gpnum_ovf(rdp->mynode, rdp);
invoke_rcu_core();
}
+// Has rcu_init() been invoked? This is used (for example) to determine
+// whether spinlocks may be acquired safely.
+static bool rcu_init_invoked(void)
+{
+ return !!rcu_state.n_online_cpus;
+}
+
+// Make the polled API aware of the beginning of a grace period.
+static void rcu_poll_gp_seq_start(unsigned long *snap)
+{
+ struct rcu_node *rnp = rcu_get_root();
+
+ if (rcu_init_invoked())
+ raw_lockdep_assert_held_rcu_node(rnp);
+
+ // If RCU was idle, note beginning of GP.
+ if (!rcu_seq_state(rcu_state.gp_seq_polled))
+ rcu_seq_start(&rcu_state.gp_seq_polled);
+
+ // Either way, record current state.
+ *snap = rcu_state.gp_seq_polled;
+}
+
+// Make the polled API aware of the end of a grace period.
+static void rcu_poll_gp_seq_end(unsigned long *snap)
+{
+ struct rcu_node *rnp = rcu_get_root();
+
+ if (rcu_init_invoked())
+ raw_lockdep_assert_held_rcu_node(rnp);
+
+ // If the previously noted GP is still in effect, record the
+ // end of that GP. Either way, zero counter to avoid counter-wrap
+ // problems.
+ if (*snap && *snap == rcu_state.gp_seq_polled) {
+ rcu_seq_end(&rcu_state.gp_seq_polled);
+ rcu_state.gp_seq_polled_snap = 0;
+ rcu_state.gp_seq_polled_exp_snap = 0;
+ } else {
+ *snap = 0;
+ }
+}
+
+// Make the polled API aware of the beginning of a grace period, but
+// where caller does not hold the root rcu_node structure's lock.
+static void rcu_poll_gp_seq_start_unlocked(unsigned long *snap)
+{
+ struct rcu_node *rnp = rcu_get_root();
+
+ if (rcu_init_invoked()) {
+ lockdep_assert_irqs_enabled();
+ raw_spin_lock_irq_rcu_node(rnp);
+ }
+ rcu_poll_gp_seq_start(snap);
+ if (rcu_init_invoked())
+ raw_spin_unlock_irq_rcu_node(rnp);
+}
+
+// Make the polled API aware of the end of a grace period, but where
+// caller does not hold the root rcu_node structure's lock.
+static void rcu_poll_gp_seq_end_unlocked(unsigned long *snap)
+{
+ struct rcu_node *rnp = rcu_get_root();
+
+ if (rcu_init_invoked()) {
+ lockdep_assert_irqs_enabled();
+ raw_spin_lock_irq_rcu_node(rnp);
+ }
+ rcu_poll_gp_seq_end(snap);
+ if (rcu_init_invoked())
+ raw_spin_unlock_irq_rcu_node(rnp);
+}
+
/*
* Initialize a new grace period. Return false if no grace period required.
*/
rcu_seq_start(&rcu_state.gp_seq);
ASSERT_EXCLUSIVE_WRITER(rcu_state.gp_seq);
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, TPS("start"));
+ rcu_poll_gp_seq_start(&rcu_state.gp_seq_polled_snap);
raw_spin_unlock_irq_rcu_node(rnp);
/*
*/
static noinline_for_stack void rcu_gp_fqs_loop(void)
{
- bool first_gp_fqs;
+ bool first_gp_fqs = true;
int gf = 0;
unsigned long j;
int ret;
struct rcu_node *rnp = rcu_get_root();
- first_gp_fqs = true;
j = READ_ONCE(jiffies_till_first_fqs);
if (rcu_state.cbovld)
gf = RCU_GP_FLAG_OVLD;
ret = 0;
for (;;) {
- if (!ret) {
+ if (rcu_state.cbovld) {
+ j = (j + 2) / 3;
+ if (j <= 0)
+ j = 1;
+ }
+ if (!ret || time_before(jiffies + j, rcu_state.jiffies_force_qs)) {
WRITE_ONCE(rcu_state.jiffies_force_qs, jiffies + j);
/*
* jiffies_force_qs before RCU_GP_WAIT_FQS state
rcu_gp_torture_wait();
WRITE_ONCE(rcu_state.gp_state, RCU_GP_DOING_FQS);
/* Locking provides needed memory barriers. */
- /* If grace period done, leave loop. */
+ /*
+ * Exit the loop if the root rcu_node structure indicates that the grace period
+ * has ended, leave the loop. The rcu_preempt_blocked_readers_cgp(rnp) check
+ * is required only for single-node rcu_node trees because readers blocking
+ * the current grace period are queued only on leaf rcu_node structures.
+ * For multi-node trees, checking the root node's ->qsmask suffices, because a
+ * given root node's ->qsmask bit is cleared only when all CPUs and tasks from
+ * the corresponding leaf nodes have passed through their quiescent state.
+ */
if (!READ_ONCE(rnp->qsmask) &&
!rcu_preempt_blocked_readers_cgp(rnp))
break;
* safe for us to drop the lock in order to mark the grace
* period as completed in all of the rcu_node structures.
*/
+ rcu_poll_gp_seq_end(&rcu_state.gp_seq_polled_snap);
raw_spin_unlock_irq_rcu_node(rnp);
/*
trace_rcu_batch_end(rcu_state.name, 0,
!rcu_segcblist_empty(&rdp->cblist),
need_resched(), is_idle_task(current),
- rcu_is_callbacks_kthread());
+ rcu_is_callbacks_kthread(rdp));
return;
}
rcu_nocb_lock_irqsave(rdp, flags);
rdp->n_cbs_invoked += count;
trace_rcu_batch_end(rcu_state.name, count, !!rcl.head, need_resched(),
- is_idle_task(current), rcu_is_callbacks_kthread());
+ is_idle_task(current), rcu_is_callbacks_kthread(rdp));
/* Update counts and requeue any remaining callbacks. */
rcu_segcblist_insert_done_cbs(&rdp->cblist, &rcl);
* @krw_arr: Array of batches of kfree_rcu() objects waiting for a grace period
* @lock: Synchronize access to this structure
* @monitor_work: Promote @head to @head_free after KFREE_DRAIN_JIFFIES
- * @monitor_todo: Tracks whether a @monitor_work delayed work is pending
* @initialized: The @rcu_work fields have been initialized
* @count: Number of objects for which GP not started
* @bkvcache:
struct kfree_rcu_cpu_work krw_arr[KFREE_N_BATCHES];
raw_spinlock_t lock;
struct delayed_work monitor_work;
- bool monitor_todo;
bool initialized;
int count;
}
}
+static bool
+need_offload_krc(struct kfree_rcu_cpu *krcp)
+{
+ int i;
+
+ for (i = 0; i < FREE_N_CHANNELS; i++)
+ if (krcp->bkvhead[i])
+ return true;
+
+ return !!krcp->head;
+}
+
/*
* This function is invoked after the KFREE_DRAIN_JIFFIES timeout.
*/
// of the channels that is still busy we should rearm the
// work to repeat an attempt. Because previous batches are
// still in progress.
- if (!krcp->bkvhead[0] && !krcp->bkvhead[1] && !krcp->head)
- krcp->monitor_todo = false;
- else
+ if (need_offload_krc(krcp))
schedule_delayed_work(&krcp->monitor_work, KFREE_DRAIN_JIFFIES);
raw_spin_unlock_irqrestore(&krcp->lock, flags);
WRITE_ONCE(krcp->count, krcp->count + 1);
// Set timer to drain after KFREE_DRAIN_JIFFIES.
- if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING &&
- !krcp->monitor_todo) {
- krcp->monitor_todo = true;
+ if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING)
schedule_delayed_work(&krcp->monitor_work, KFREE_DRAIN_JIFFIES);
- }
unlock_return:
krc_this_cpu_unlock(krcp, flags);
struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);
raw_spin_lock_irqsave(&krcp->lock, flags);
- if ((!krcp->bkvhead[0] && !krcp->bkvhead[1] && !krcp->head) ||
- krcp->monitor_todo) {
- raw_spin_unlock_irqrestore(&krcp->lock, flags);
- continue;
- }
- krcp->monitor_todo = true;
- schedule_delayed_work_on(cpu, &krcp->monitor_work,
- KFREE_DRAIN_JIFFIES);
+ if (need_offload_krc(krcp))
+ schedule_delayed_work_on(cpu, &krcp->monitor_work, KFREE_DRAIN_JIFFIES);
raw_spin_unlock_irqrestore(&krcp->lock, flags);
}
}
lock_is_held(&rcu_lock_map) ||
lock_is_held(&rcu_sched_lock_map),
"Illegal synchronize_rcu() in RCU read-side critical section");
- if (rcu_blocking_is_gp())
+ if (rcu_blocking_is_gp()) {
+ // Note well that this code runs with !PREEMPT && !SMP.
+ // In addition, all code that advances grace periods runs at
+ // process level. Therefore, this normal GP overlaps with
+ // other normal GPs only by being fully nested within them,
+ // which allows reuse of ->gp_seq_polled_snap.
+ rcu_poll_gp_seq_start_unlocked(&rcu_state.gp_seq_polled_snap);
+ rcu_poll_gp_seq_end_unlocked(&rcu_state.gp_seq_polled_snap);
+ if (rcu_init_invoked())
+ cond_resched_tasks_rcu_qs();
return; // Context allows vacuous grace periods.
+ }
if (rcu_gp_is_expedited())
synchronize_rcu_expedited();
else
* before the load from ->gp_seq.
*/
smp_mb(); /* ^^^ */
- return rcu_seq_snap(&rcu_state.gp_seq);
+ return rcu_seq_snap(&rcu_state.gp_seq_polled);
}
EXPORT_SYMBOL_GPL(get_state_synchronize_rcu);
rdp = this_cpu_ptr(&rcu_data);
rnp = rdp->mynode;
raw_spin_lock_rcu_node(rnp); // irqs already disabled.
- needwake = rcu_start_this_gp(rnp, rdp, gp_seq);
+ // Note it is possible for a grace period to have elapsed between
+ // the above call to get_state_synchronize_rcu() and the below call
+ // to rcu_seq_snap. This is OK, the worst that happens is that we
+ // get a grace period that no one needed. These accesses are ordered
+ // by smp_mb(), and we are accessing them in the opposite order
+ // from which they are updated at grace-period start, as required.
+ needwake = rcu_start_this_gp(rnp, rdp, rcu_seq_snap(&rcu_state.gp_seq));
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
if (needwake)
rcu_gp_kthread_wake();
*
* Yes, this function does not take counter wrap into account.
* But counter wrap is harmless. If the counter wraps, we have waited for
- * more than 2 billion grace periods (and way more on a 64-bit system!).
+ * more than a billion grace periods (and way more on a 64-bit system!).
* Those needing to keep oldstate values for very long time periods
* (many hours even on 32-bit systems) should check them occasionally
* and either refresh them or set a flag indicating that the grace period
*/
bool poll_state_synchronize_rcu(unsigned long oldstate)
{
- if (rcu_seq_done(&rcu_state.gp_seq, oldstate)) {
+ if (oldstate == RCU_GET_STATE_COMPLETED ||
+ rcu_seq_done_exact(&rcu_state.gp_seq_polled, oldstate)) {
smp_mb(); /* Ensure GP ends before subsequent accesses. */
return true;
}
/**
* cond_synchronize_rcu - Conditionally wait for an RCU grace period
*
- * @oldstate: value from get_state_synchronize_rcu() or start_poll_synchronize_rcu()
+ * @oldstate: value from get_state_synchronize_rcu(), start_poll_synchronize_rcu(), or start_poll_synchronize_rcu_expedited()
*
* If a full RCU grace period has elapsed since the earlier call to
* get_state_synchronize_rcu() or start_poll_synchronize_rcu(), just return.
* Otherwise, invoke synchronize_rcu() to wait for a full grace period.
*
- * Yes, this function does not take counter wrap into account. But
- * counter wrap is harmless. If the counter wraps, we have waited for
+ * Yes, this function does not take counter wrap into account.
+ * But counter wrap is harmless. If the counter wraps, we have waited for
* more than 2 billion grace periods (and way more on a 64-bit system!),
- * so waiting for one additional grace period should be just fine.
+ * so waiting for a couple of additional grace periods should be just fine.
*
* This function provides the same memory-ordering guarantees that
* would be provided by a synchronize_rcu() that was invoked at the call
- * to the function that provided @oldstate, and that returned at the end
+ * to the function that provided @oldstate and that returned at the end
* of this function.
*/
void cond_synchronize_rcu(unsigned long oldstate)
static void __init
rcu_boot_init_percpu_data(int cpu)
{
+ struct context_tracking *ct = this_cpu_ptr(&context_tracking);
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
/* Set up local state, ensuring consistent view of global state. */
rdp->grpmask = leaf_node_cpu_bit(rdp->mynode, cpu);
INIT_WORK(&rdp->strict_work, strict_work_handler);
- WARN_ON_ONCE(rdp->dynticks_nesting != 1);
- WARN_ON_ONCE(rcu_dynticks_in_eqs(rcu_dynticks_snap(rdp)));
+ WARN_ON_ONCE(ct->dynticks_nesting != 1);
+ WARN_ON_ONCE(rcu_dynticks_in_eqs(rcu_dynticks_snap(cpu)));
rdp->barrier_seq_snap = rcu_state.barrier_sequence;
rdp->rcu_ofl_gp_seq = rcu_state.gp_seq;
rdp->rcu_ofl_gp_flags = RCU_GP_CLEANED;
int rcutree_prepare_cpu(unsigned int cpu)
{
unsigned long flags;
+ struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
struct rcu_node *rnp = rcu_get_root();
rdp->qlen_last_fqs_check = 0;
rdp->n_force_qs_snap = READ_ONCE(rcu_state.n_force_qs);
rdp->blimit = blimit;
- rdp->dynticks_nesting = 1; /* CPU not up, no tearing. */
+ ct->dynticks_nesting = 1; /* CPU not up, no tearing. */
raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */
/*
rdp->rcu_ofl_gp_flags = READ_ONCE(rcu_state.gp_flags);
if (rnp->qsmask & mask) { /* RCU waiting on outgoing CPU? */
/* Report quiescent state -before- changing ->qsmaskinitnext! */
+ rcu_disable_urgency_upon_qs(rdp);
rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags);
raw_spin_lock_irqsave_rcu_node(rnp, flags);
}
needwake = needwake || rcu_advance_cbs(my_rnp, my_rdp);
rcu_segcblist_disable(&rdp->cblist);
WARN_ON_ONCE(rcu_segcblist_empty(&my_rdp->cblist) != !rcu_segcblist_n_cbs(&my_rdp->cblist));
+ check_cb_ovld_locked(my_rdp, my_rnp);
if (rcu_rdp_is_offloaded(my_rdp)) {
raw_spin_unlock_rcu_node(my_rnp); /* irqs remain disabled. */
__call_rcu_nocb_wake(my_rdp, true, flags);
init_waitqueue_head(&rnp->exp_wq[3]);
spin_lock_init(&rnp->exp_lock);
mutex_init(&rnp->boost_kthread_mutex);
+ raw_spin_lock_init(&rnp->exp_poll_lock);
+ rnp->exp_seq_poll_rq = RCU_GET_STATE_COMPLETED;
+ INIT_WORK(&rnp->exp_poll_wq, sync_rcu_do_polled_gp);
}
}
qovld_calc = DEFAULT_RCU_QOVLD_MULT * qhimark;
else
qovld_calc = qovld;
+
+ // Kick-start any polled grace periods that started early.
+ if (!(per_cpu_ptr(&rcu_data, cpu)->mynode->exp_seq_poll_rq & 0x1))
+ (void)start_poll_synchronize_rcu_expedited();
}
#include "tree_stall.h"
git.samba.org / sfrench / cifs-2.6.git / blobdiff