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Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Browse Source 
Pull RCU updates from Ingo Molnar:

 - updates to the handling of expedited grace periods

 - updates to reduce lock contention in the rcu_node combining tree

   [ These are in preparation for the consolidation of RCU-bh,
     RCU-preempt, and RCU-sched into a single flavor, which was
     requested by Linus in response to a security flaw whose root cause
     included confusion between the multiple flavors of RCU ]

 - torture-test updates that save their users some time and effort

 - miscellaneous fixes

* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (44 commits)
  rcu/x86: Provide early rcu_cpu_starting() callback
  torture: Make kvm-find-errors.sh find build warnings
  rcutorture: Abbreviate kvm.sh summary lines
  rcutorture: Print end-of-test state in kvm.sh summary
  rcutorture: Print end-of-test state
  torture: Fold parse-torture.sh into parse-console.sh
  torture: Add a script to edit output from failed runs
  rcu: Update list of rcu_future_grace_period() trace events
  rcu: Drop early GP request check from rcu_gp_kthread()
  rcu: Simplify and inline cpu_needs_another_gp()
  rcu: The rcu_gp_cleanup() function does not need cpu_needs_another_gp()
  rcu: Make rcu_start_this_gp() check for out-of-range requests
  rcu: Add funnel locking to rcu_start_this_gp()
  rcu: Make rcu_start_future_gp() caller select grace period
  rcu: Inline rcu_start_gp_advanced() into rcu_start_future_gp()
  rcu: Clear request other than RCU_GP_FLAG_INIT at GP end
  rcu: Cleanup, don't put ->completed into an int
  rcu: Switch __rcu_process_callbacks() to rcu_accelerate_cbs()
  rcu: Avoid __call_rcu_core() root rcu_node ->lock acquisition
  rcu: Make rcu_migrate_callbacks wake GP kthread when needed
  ...
This commit is contained in:
Linus Torvalds
2018-06-04 15:54:04 -07:00
parent 137f5ae4da 52f2b34f46
commit 4057adafb3
31 changed files with 635 additions and 633 deletions
Download Patch File Download Diff File Expand all files Collapse all files

12
kernel/rcu/rcu.h
View File

@@ -270,6 +270,12 @@ static inline void rcu_init_levelspread(int *levelspread, const int *levelcnt)
}
}
/* Returns first leaf rcu_node of the specified RCU flavor. */
#define rcu_first_leaf_node(rsp) ((rsp)->level[rcu_num_lvls - 1])
/* Is this rcu_node a leaf? */
#define rcu_is_leaf_node(rnp) ((rnp)->level == rcu_num_lvls - 1)
/*
* Do a full breadth-first scan of the rcu_node structures for the
* specified rcu_state structure.
@@ -284,8 +290,7 @@ static inline void rcu_init_levelspread(int *levelspread, const int *levelcnt)
* rcu_node tree with but one rcu_node structure, this loop is a no-op.
*/
#define rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) \
for ((rnp) = &(rsp)->node[0]; \
(rnp) < (rsp)->level[rcu_num_lvls - 1]; (rnp)++)
for ((rnp) = &(rsp)->node[0]; !rcu_is_leaf_node(rsp, rnp); (rnp)++)
/*
* Scan the leaves of the rcu_node hierarchy for the specified rcu_state
@@ -294,7 +299,7 @@ static inline void rcu_init_levelspread(int *levelspread, const int *levelcnt)
* It is still a leaf node, even if it is also the root node.
*/
#define rcu_for_each_leaf_node(rsp, rnp) \
for ((rnp) = (rsp)->level[rcu_num_lvls - 1]; \
for ((rnp) = rcu_first_leaf_node(rsp); \
(rnp) < &(rsp)->node[rcu_num_nodes]; (rnp)++)
/*
@@ -486,6 +491,7 @@ void rcu_force_quiescent_state(void);
void rcu_bh_force_quiescent_state(void);
void rcu_sched_force_quiescent_state(void);
extern struct workqueue_struct *rcu_gp_wq;
extern struct workqueue_struct *rcu_par_gp_wq;
#endif /* #else #ifdef CONFIG_TINY_RCU */
#ifdef CONFIG_RCU_NOCB_CPU

18
kernel/rcu/rcu_segcblist.c
View File

@@ -403,24 +403,6 @@ bool rcu_segcblist_accelerate(struct rcu_segcblist *rsclp, unsigned long seq)
return true;
}
/*
* Scan the specified rcu_segcblist structure for callbacks that need
* a grace period later than the one specified by "seq". We don't look
* at the RCU_DONE_TAIL or RCU_NEXT_TAIL segments because they don't
* have a grace-period sequence number.
*/
bool rcu_segcblist_future_gp_needed(struct rcu_segcblist *rsclp,
unsigned long seq)
{
int i;
for (i = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++)
if (rsclp->tails[i - 1] != rsclp->tails[i] &&
ULONG_CMP_LT(seq, rsclp->gp_seq[i]))
return true;
return false;
}
/*
* Merge the source rcu_segcblist structure into the destination
* rcu_segcblist structure, then initialize the source. Any pending

2
kernel/rcu/rcu_segcblist.h
View File

@@ -134,7 +134,5 @@ void rcu_segcblist_insert_pend_cbs(struct rcu_segcblist *rsclp,
struct rcu_cblist *rclp);
void rcu_segcblist_advance(struct rcu_segcblist *rsclp, unsigned long seq);
bool rcu_segcblist_accelerate(struct rcu_segcblist *rsclp, unsigned long seq);
bool rcu_segcblist_future_gp_needed(struct rcu_segcblist *rsclp,
unsigned long seq);
void rcu_segcblist_merge(struct rcu_segcblist *dst_rsclp,
struct rcu_segcblist *src_rsclp);

2
kernel/rcu/rcuperf.c
View File

@@ -369,7 +369,7 @@ static bool __maybe_unused torturing_tasks(void)
*/
static void rcu_perf_wait_shutdown(void)
{
cond_resched_rcu_qs();
cond_resched_tasks_rcu_qs();
if (atomic_read(&n_rcu_perf_writer_finished) < nrealwriters)
return;
while (!torture_must_stop())

15
kernel/rcu/rcutorture.c
View File

@@ -593,7 +593,12 @@ static void srcu_torture_init(void)
static void srcu_torture_cleanup(void)
{
cleanup_srcu_struct(&srcu_ctld);
static DEFINE_TORTURE_RANDOM(rand);
if (torture_random(&rand) & 0x800)
cleanup_srcu_struct(&srcu_ctld);
else
cleanup_srcu_struct_quiesced(&srcu_ctld);
srcu_ctlp = &srcu_ctl; /* In case of a later rcutorture run. */
}
@@ -1609,6 +1614,9 @@ static enum cpuhp_state rcutor_hp;
static void
rcu_torture_cleanup(void)
{
int flags = 0;
unsigned long gpnum = 0;
unsigned long completed = 0;
int i;
rcutorture_record_test_transition();
@@ -1639,6 +1647,11 @@ rcu_torture_cleanup(void)
fakewriter_tasks = NULL;
}
rcutorture_get_gp_data(cur_ops->ttype, &flags, &gpnum, &completed);
srcutorture_get_gp_data(cur_ops->ttype, srcu_ctlp,
&flags, &gpnum, &completed);
pr_alert("%s: End-test grace-period state: g%lu c%lu f%#x\n",
cur_ops->name, gpnum, completed, flags);
torture_stop_kthread(rcu_torture_stats, stats_task);
torture_stop_kthread(rcu_torture_fqs, fqs_task);
for (i = 0; i < ncbflooders; i++)

9
kernel/rcu/srcutiny.c
View File

@@ -86,16 +86,19 @@ EXPORT_SYMBOL_GPL(init_srcu_struct);
* Must invoke this after you are finished using a given srcu_struct that
* was initialized via init_srcu_struct(), else you leak memory.
*/
void cleanup_srcu_struct(struct srcu_struct *sp)
void _cleanup_srcu_struct(struct srcu_struct *sp, bool quiesced)
{
WARN_ON(sp->srcu_lock_nesting[0] || sp->srcu_lock_nesting[1]);
flush_work(&sp->srcu_work);
if (quiesced)
WARN_ON(work_pending(&sp->srcu_work));
else
flush_work(&sp->srcu_work);
WARN_ON(sp->srcu_gp_running);
WARN_ON(sp->srcu_gp_waiting);
WARN_ON(sp->srcu_cb_head);
WARN_ON(&sp->srcu_cb_head != sp->srcu_cb_tail);
}
EXPORT_SYMBOL_GPL(cleanup_srcu_struct);
EXPORT_SYMBOL_GPL(_cleanup_srcu_struct);
/*
* Removes the count for the old reader from the appropriate element of

30
kernel/rcu/srcutree.c
View File

@@ -366,24 +366,28 @@ static unsigned long srcu_get_delay(struct srcu_struct *sp)
return SRCU_INTERVAL;
}
/**
* cleanup_srcu_struct - deconstruct a sleep-RCU structure
* @sp: structure to clean up.
*
* Must invoke this after you are finished using a given srcu_struct that
* was initialized via init_srcu_struct(), else you leak memory.
*/
void cleanup_srcu_struct(struct srcu_struct *sp)
/* Helper for cleanup_srcu_struct() and cleanup_srcu_struct_quiesced(). */
void _cleanup_srcu_struct(struct srcu_struct *sp, bool quiesced)
{
int cpu;
if (WARN_ON(!srcu_get_delay(sp)))
return; /* Leakage unless caller handles error. */
return; /* Just leak it! */
if (WARN_ON(srcu_readers_active(sp)))
return; /* Leakage unless caller handles error. */
flush_delayed_work(&sp->work);
return; /* Just leak it! */
if (quiesced) {
if (WARN_ON(delayed_work_pending(&sp->work)))
return; /* Just leak it! */
} else {
flush_delayed_work(&sp->work);
}
for_each_possible_cpu(cpu)
flush_delayed_work(&per_cpu_ptr(sp->sda, cpu)->work);
if (quiesced) {
if (WARN_ON(delayed_work_pending(&per_cpu_ptr(sp->sda, cpu)->work)))
return; /* Just leak it! */
} else {
flush_delayed_work(&per_cpu_ptr(sp->sda, cpu)->work);
}
if (WARN_ON(rcu_seq_state(READ_ONCE(sp->srcu_gp_seq)) != SRCU_STATE_IDLE) ||
WARN_ON(srcu_readers_active(sp))) {
pr_info("%s: Active srcu_struct %p state: %d\n", __func__, sp, rcu_seq_state(READ_ONCE(sp->srcu_gp_seq)));
@@ -392,7 +396,7 @@ void cleanup_srcu_struct(struct srcu_struct *sp)
free_percpu(sp->sda);
sp->sda = NULL;
}
EXPORT_SYMBOL_GPL(cleanup_srcu_struct);
EXPORT_SYMBOL_GPL(_cleanup_srcu_struct);
/*
* Counts the new reader in the appropriate per-CPU element of the

366
kernel/rcu/tree.c
View File

@@ -524,8 +524,6 @@ module_param(rcu_kick_kthreads, bool, 0644);
static ulong jiffies_till_sched_qs = HZ / 10;
module_param(jiffies_till_sched_qs, ulong, 0444);
static bool rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp,
struct rcu_data *rdp);
static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *rsp));
static void force_quiescent_state(struct rcu_state *rsp);
static int rcu_pending(void);
@@ -710,44 +708,6 @@ static struct rcu_node *rcu_get_root(struct rcu_state *rsp)
return &rsp->node[0];
}
/*
* Is there any need for future grace periods?
* Interrupts must be disabled. If the caller does not hold the root
* rnp_node structure's ->lock, the results are advisory only.
*/
static int rcu_future_needs_gp(struct rcu_state *rsp)
{
struct rcu_node *rnp = rcu_get_root(rsp);
int idx = (READ_ONCE(rnp->completed) + 1) & 0x1;
int *fp = &rnp->need_future_gp[idx];
lockdep_assert_irqs_disabled();
return READ_ONCE(*fp);
}
/*
* Does the current CPU require a not-yet-started grace period?
* The caller must have disabled interrupts to prevent races with
* normal callback registry.
*/
static bool
cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp)
{
lockdep_assert_irqs_disabled();
if (rcu_gp_in_progress(rsp))
return false; /* No, a grace period is already in progress. */
if (rcu_future_needs_gp(rsp))
return true; /* Yes, a no-CBs CPU needs one. */
if (!rcu_segcblist_is_enabled(&rdp->cblist))
return false; /* No, this is a no-CBs (or offline) CPU. */
if (!rcu_segcblist_restempty(&rdp->cblist, RCU_NEXT_READY_TAIL))
return true; /* Yes, CPU has newly registered callbacks. */
if (rcu_segcblist_future_gp_needed(&rdp->cblist,
READ_ONCE(rsp->completed)))
return true; /* Yes, CBs for future grace period. */
return false; /* No grace period needed. */
}
/*
* Enter an RCU extended quiescent state, which can be either the
* idle loop or adaptive-tickless usermode execution.
@@ -1234,10 +1194,10 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
}
/*
* Has this CPU encountered a cond_resched_rcu_qs() since the
* beginning of the grace period? For this to be the case,
* the CPU has to have noticed the current grace period. This
* might not be the case for nohz_full CPUs looping in the kernel.
* Has this CPU encountered a cond_resched() since the beginning
* of the grace period? For this to be the case, the CPU has to
* have noticed the current grace period. This might not be the
* case for nohz_full CPUs looping in the kernel.
*/
jtsq = jiffies_till_sched_qs;
ruqp = per_cpu_ptr(&rcu_dynticks.rcu_urgent_qs, rdp->cpu);
@@ -1641,6 +1601,21 @@ static unsigned long rcu_cbs_completed(struct rcu_state *rsp,
if (rcu_get_root(rsp) == rnp && rnp->gpnum == rnp->completed)
return rnp->completed + 1;
/*
* If the current rcu_node structure believes that RCU is
* idle, and if the rcu_state structure does not yet reflect
* the start of a new grace period, then the next grace period
* will suffice. The memory barrier is needed to accurately
* sample the rsp->gpnum, and pairs with the second lock
* acquisition in rcu_gp_init(), which is augmented with
* smp_mb__after_unlock_lock() for this purpose.
*/
if (rnp->gpnum == rnp->completed) {
smp_mb(); /* See above block comment. */
if (READ_ONCE(rsp->gpnum) == rnp->completed)
return rnp->completed + 1;
}
/*
* Otherwise, wait for a possible partial grace period and
* then the subsequent full grace period.
@@ -1648,12 +1623,9 @@ static unsigned long rcu_cbs_completed(struct rcu_state *rsp,
return rnp->completed + 2;
}
/*
* Trace-event helper function for rcu_start_future_gp() and
* rcu_nocb_wait_gp().
*/
static void trace_rcu_future_gp(struct rcu_node *rnp, struct rcu_data *rdp,
unsigned long c, const char *s)
/* Trace-event wrapper function for trace_rcu_future_grace_period. */
static void trace_rcu_this_gp(struct rcu_node *rnp, struct rcu_data *rdp,
unsigned long c, const char *s)
{
trace_rcu_future_grace_period(rdp->rsp->name, rnp->gpnum,
rnp->completed, c, rnp->level,
@@ -1661,96 +1633,67 @@ static void trace_rcu_future_gp(struct rcu_node *rnp, struct rcu_data *rdp,
}
/*
* Start some future grace period, as needed to handle newly arrived
* Start the specified grace period, as needed to handle newly arrived
* callbacks. The required future grace periods are recorded in each
* rcu_node structure's ->need_future_gp field. Returns true if there
* rcu_node structure's ->need_future_gp[] field. Returns true if there
* is reason to awaken the grace-period kthread.
*
* The caller must hold the specified rcu_node structure's ->lock.
* The caller must hold the specified rcu_node structure's ->lock, which
* is why the caller is responsible for waking the grace-period kthread.
*/
static bool __maybe_unused
rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp,
unsigned long *c_out)
static bool rcu_start_this_gp(struct rcu_node *rnp, struct rcu_data *rdp,
unsigned long c)
{
unsigned long c;
bool ret = false;
struct rcu_node *rnp_root = rcu_get_root(rdp->rsp);
struct rcu_state *rsp = rdp->rsp;
struct rcu_node *rnp_root;
/*
* Use funnel locking to either acquire the root rcu_node
* structure's lock or bail out if the need for this grace period
* has already been recorded -- or has already started. If there
* is already a grace period in progress in a non-leaf node, no
* recording is needed because the end of the grace period will
* scan the leaf rcu_node structures. Note that rnp->lock must
* not be released.
*/
raw_lockdep_assert_held_rcu_node(rnp);
/*
* Pick up grace-period number for new callbacks. If this
* grace period is already marked as needed, return to the caller.
*/
c = rcu_cbs_completed(rdp->rsp, rnp);
trace_rcu_future_gp(rnp, rdp, c, TPS("Startleaf"));
if (rnp->need_future_gp[c & 0x1]) {
trace_rcu_future_gp(rnp, rdp, c, TPS("Prestartleaf"));
goto out;
trace_rcu_this_gp(rnp, rdp, c, TPS("Startleaf"));
for (rnp_root = rnp; 1; rnp_root = rnp_root->parent) {
if (rnp_root != rnp)
raw_spin_lock_rcu_node(rnp_root);
WARN_ON_ONCE(ULONG_CMP_LT(rnp_root->gpnum +
need_future_gp_mask(), c));
if (need_future_gp_element(rnp_root, c) ||
ULONG_CMP_GE(rnp_root->gpnum, c) ||
(rnp != rnp_root &&
rnp_root->gpnum != rnp_root->completed)) {
trace_rcu_this_gp(rnp_root, rdp, c, TPS("Prestarted"));
goto unlock_out;
}
need_future_gp_element(rnp_root, c) = true;
if (rnp_root != rnp && rnp_root->parent != NULL)
raw_spin_unlock_rcu_node(rnp_root);
if (!rnp_root->parent)
break; /* At root, and perhaps also leaf. */
}
/*
* If either this rcu_node structure or the root rcu_node structure
* believe that a grace period is in progress, then we must wait
* for the one following, which is in "c". Because our request
* will be noticed at the end of the current grace period, we don't
* need to explicitly start one. We only do the lockless check
* of rnp_root's fields if the current rcu_node structure thinks
* there is no grace period in flight, and because we hold rnp->lock,
* the only possible change is when rnp_root's two fields are
* equal, in which case rnp_root->gpnum might be concurrently
* incremented. But that is OK, as it will just result in our
* doing some extra useless work.
*/
if (rnp->gpnum != rnp->completed ||
READ_ONCE(rnp_root->gpnum) != READ_ONCE(rnp_root->completed)) {
rnp->need_future_gp[c & 0x1]++;
trace_rcu_future_gp(rnp, rdp, c, TPS("Startedleaf"));
goto out;
}
/*
* There might be no grace period in progress. If we don't already
* hold it, acquire the root rcu_node structure's lock in order to
* start one (if needed).
*/
if (rnp != rnp_root)
raw_spin_lock_rcu_node(rnp_root);
/*
* Get a new grace-period number. If there really is no grace
* period in progress, it will be smaller than the one we obtained
* earlier. Adjust callbacks as needed.
*/
c = rcu_cbs_completed(rdp->rsp, rnp_root);
if (!rcu_is_nocb_cpu(rdp->cpu))
(void)rcu_segcblist_accelerate(&rdp->cblist, c);
/*
* If the needed for the required grace period is already
* recorded, trace and leave.
*/
if (rnp_root->need_future_gp[c & 0x1]) {
trace_rcu_future_gp(rnp, rdp, c, TPS("Prestartedroot"));
/* If GP already in progress, just leave, otherwise start one. */
if (rnp_root->gpnum != rnp_root->completed) {
trace_rcu_this_gp(rnp_root, rdp, c, TPS("Startedleafroot"));
goto unlock_out;
}
/* Record the need for the future grace period. */
rnp_root->need_future_gp[c & 0x1]++;
/* If a grace period is not already in progress, start one. */
if (rnp_root->gpnum != rnp_root->completed) {
trace_rcu_future_gp(rnp, rdp, c, TPS("Startedleafroot"));
} else {
trace_rcu_future_gp(rnp, rdp, c, TPS("Startedroot"));
ret = rcu_start_gp_advanced(rdp->rsp, rnp_root, rdp);
trace_rcu_this_gp(rnp_root, rdp, c, TPS("Startedroot"));
WRITE_ONCE(rsp->gp_flags, rsp->gp_flags | RCU_GP_FLAG_INIT);
if (!rsp->gp_kthread) {
trace_rcu_this_gp(rnp_root, rdp, c, TPS("NoGPkthread"));
goto unlock_out;
}
trace_rcu_grace_period(rsp->name, READ_ONCE(rsp->gpnum), TPS("newreq"));
ret = true; /* Caller must wake GP kthread. */
unlock_out:
if (rnp != rnp_root)
raw_spin_unlock_rcu_node(rnp_root);
out:
if (c_out != NULL)
*c_out = c;
return ret;
}
@@ -1758,16 +1701,16 @@ out:
* Clean up any old requests for the just-ended grace period. Also return
* whether any additional grace periods have been requested.
*/
static int rcu_future_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp)
static bool rcu_future_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp)
{
int c = rnp->completed;
int needmore;
unsigned long c = rnp->completed;
bool needmore;
struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
rnp->need_future_gp[c & 0x1] = 0;
needmore = rnp->need_future_gp[(c + 1) & 0x1];
trace_rcu_future_gp(rnp, rdp, c,
needmore ? TPS("CleanupMore") : TPS("Cleanup"));
need_future_gp_element(rnp, c) = false;
needmore = need_any_future_gp(rnp);
trace_rcu_this_gp(rnp, rdp, c,
needmore ? TPS("CleanupMore") : TPS("Cleanup"));
return needmore;
}
@@ -1802,6 +1745,7 @@ static void rcu_gp_kthread_wake(struct rcu_state *rsp)
static bool rcu_accelerate_cbs(struct rcu_state *rsp, struct rcu_node *rnp,
struct rcu_data *rdp)
{
unsigned long c;
bool ret = false;
raw_lockdep_assert_held_rcu_node(rnp);
@@ -1820,8 +1764,9 @@ static bool rcu_accelerate_cbs(struct rcu_state *rsp, struct rcu_node *rnp,
* accelerating callback invocation to an earlier grace-period
* number.
*/
if (rcu_segcblist_accelerate(&rdp->cblist, rcu_cbs_completed(rsp, rnp)))
ret = rcu_start_future_gp(rnp, rdp, NULL);
c = rcu_cbs_completed(rsp, rnp);
if (rcu_segcblist_accelerate(&rdp->cblist, c))
ret = rcu_start_this_gp(rnp, rdp, c);
/* Trace depending on how much we were able to accelerate. */
if (rcu_segcblist_restempty(&rdp->cblist, RCU_WAIT_TAIL))
@@ -2049,7 +1994,7 @@ static bool rcu_gp_init(struct rcu_state *rsp)
rnp->level, rnp->grplo,
rnp->grphi, rnp->qsmask);
raw_spin_unlock_irq_rcu_node(rnp);
cond_resched_rcu_qs();
cond_resched_tasks_rcu_qs();
WRITE_ONCE(rsp->gp_activity, jiffies);
}
@@ -2108,7 +2053,6 @@ static void rcu_gp_cleanup(struct rcu_state *rsp)
{
unsigned long gp_duration;
bool needgp = false;
int nocb = 0;
struct rcu_data *rdp;
struct rcu_node *rnp = rcu_get_root(rsp);
struct swait_queue_head *sq;
@@ -2147,31 +2091,35 @@ static void rcu_gp_cleanup(struct rcu_state *rsp)
if (rnp == rdp->mynode)
needgp = __note_gp_changes(rsp, rnp, rdp) || needgp;
/* smp_mb() provided by prior unlock-lock pair. */
nocb += rcu_future_gp_cleanup(rsp, rnp);
needgp = rcu_future_gp_cleanup(rsp, rnp) || needgp;
sq = rcu_nocb_gp_get(rnp);
raw_spin_unlock_irq_rcu_node(rnp);
rcu_nocb_gp_cleanup(sq);
cond_resched_rcu_qs();
cond_resched_tasks_rcu_qs();
WRITE_ONCE(rsp->gp_activity, jiffies);
rcu_gp_slow(rsp, gp_cleanup_delay);
}
rnp = rcu_get_root(rsp);
raw_spin_lock_irq_rcu_node(rnp); /* Order GP before ->completed update. */
rcu_nocb_gp_set(rnp, nocb);
/* Declare grace period done. */
WRITE_ONCE(rsp->completed, rsp->gpnum);
trace_rcu_grace_period(rsp->name, rsp->completed, TPS("end"));
rsp->gp_state = RCU_GP_IDLE;
/* Check for GP requests since above loop. */
rdp = this_cpu_ptr(rsp->rda);
if (need_any_future_gp(rnp)) {
trace_rcu_this_gp(rnp, rdp, rsp->completed - 1,
TPS("CleanupMore"));
needgp = true;
}
/* Advance CBs to reduce false positives below. */
needgp = rcu_advance_cbs(rsp, rnp, rdp) || needgp;
if (needgp || cpu_needs_another_gp(rsp, rdp)) {
if (!rcu_accelerate_cbs(rsp, rnp, rdp) && needgp) {
WRITE_ONCE(rsp->gp_flags, RCU_GP_FLAG_INIT);
trace_rcu_grace_period(rsp->name,
READ_ONCE(rsp->gpnum),
trace_rcu_grace_period(rsp->name, READ_ONCE(rsp->gpnum),
TPS("newreq"));
}
WRITE_ONCE(rsp->gp_flags, rsp->gp_flags & RCU_GP_FLAG_INIT);
raw_spin_unlock_irq_rcu_node(rnp);
}
@@ -2202,7 +2150,7 @@ static int __noreturn rcu_gp_kthread(void *arg)
/* Locking provides needed memory barrier. */
if (rcu_gp_init(rsp))
break;
cond_resched_rcu_qs();
cond_resched_tasks_rcu_qs();
WRITE_ONCE(rsp->gp_activity, jiffies);
WARN_ON(signal_pending(current));
trace_rcu_grace_period(rsp->name,
@@ -2247,7 +2195,7 @@ static int __noreturn rcu_gp_kthread(void *arg)
trace_rcu_grace_period(rsp->name,
READ_ONCE(rsp->gpnum),
TPS("fqsend"));
cond_resched_rcu_qs();
cond_resched_tasks_rcu_qs();
WRITE_ONCE(rsp->gp_activity, jiffies);
ret = 0; /* Force full wait till next FQS. */
j = jiffies_till_next_fqs;
@@ -2260,7 +2208,7 @@ static int __noreturn rcu_gp_kthread(void *arg)
}
} else {
/* Deal with stray signal. */
cond_resched_rcu_qs();
cond_resched_tasks_rcu_qs();
WRITE_ONCE(rsp->gp_activity, jiffies);
WARN_ON(signal_pending(current));
trace_rcu_grace_period(rsp->name,
@@ -2282,71 +2230,6 @@ static int __noreturn rcu_gp_kthread(void *arg)
}
}
/*
* Start a new RCU grace period if warranted, re-initializing the hierarchy
* in preparation for detecting the next grace period. The caller must hold
* the root node's ->lock and hard irqs must be disabled.
*
* Note that it is legal for a dying CPU (which is marked as offline) to
* invoke this function. This can happen when the dying CPU reports its
* quiescent state.
*
* Returns true if the grace-period kthread must be awakened.
*/
static bool
rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp,
struct rcu_data *rdp)
{
raw_lockdep_assert_held_rcu_node(rnp);
if (!rsp->gp_kthread || !cpu_needs_another_gp(rsp, rdp)) {
/*
* Either we have not yet spawned the grace-period
* task, this CPU does not need another grace period,
* or a grace period is already in progress.
* Either way, don't start a new grace period.
*/
return false;
}
WRITE_ONCE(rsp->gp_flags, RCU_GP_FLAG_INIT);
trace_rcu_grace_period(rsp->name, READ_ONCE(rsp->gpnum),
TPS("newreq"));
/*
* We can't do wakeups while holding the rnp->lock, as that
* could cause possible deadlocks with the rq->lock. Defer
* the wakeup to our caller.
*/
return true;
}
/*
* Similar to rcu_start_gp_advanced(), but also advance the calling CPU's
* callbacks. Note that rcu_start_gp_advanced() cannot do this because it
* is invoked indirectly from rcu_advance_cbs(), which would result in
* endless recursion -- or would do so if it wasn't for the self-deadlock
* that is encountered beforehand.
*
* Returns true if the grace-period kthread needs to be awakened.
*/
static bool rcu_start_gp(struct rcu_state *rsp)
{
struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
struct rcu_node *rnp = rcu_get_root(rsp);
bool ret = false;
/*
* If there is no grace period in progress right now, any
* callbacks we have up to this point will be satisfied by the
* next grace period. Also, advancing the callbacks reduces the
* probability of false positives from cpu_needs_another_gp()
* resulting in pointless grace periods. So, advance callbacks
* then start the grace period!
*/
ret = rcu_advance_cbs(rsp, rnp, rdp) || ret;
ret = rcu_start_gp_advanced(rsp, rnp, rdp) || ret;
return ret;
}
/*
* Report a full set of quiescent states to the specified rcu_state data
* structure. Invoke rcu_gp_kthread_wake() to awaken the grace-period
@@ -2398,7 +2281,7 @@ rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp,
return;
}
WARN_ON_ONCE(oldmask); /* Any child must be all zeroed! */
WARN_ON_ONCE(rnp->level != rcu_num_lvls - 1 &&
WARN_ON_ONCE(!rcu_is_leaf_node(rnp) &&
rcu_preempt_blocked_readers_cgp(rnp));
rnp->qsmask &= ~mask;
trace_rcu_quiescent_state_report(rsp->name, rnp->gpnum,
@@ -2782,7 +2665,7 @@ static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *rsp))
struct rcu_node *rnp;
rcu_for_each_leaf_node(rsp, rnp) {
cond_resched_rcu_qs();
cond_resched_tasks_rcu_qs();
mask = 0;
raw_spin_lock_irqsave_rcu_node(rnp, flags);
if (rnp->qsmask == 0) {
@@ -2874,22 +2757,27 @@ __rcu_process_callbacks(struct rcu_state *rsp)
unsigned long flags;
bool needwake;
struct rcu_data *rdp = raw_cpu_ptr(rsp->rda);
struct rcu_node *rnp;
WARN_ON_ONCE(!rdp->beenonline);
/* Update RCU state based on any recent quiescent states. */
rcu_check_quiescent_state(rsp, rdp);
/* Does this CPU require a not-yet-started grace period? */
local_irq_save(flags);
if (cpu_needs_another_gp(rsp, rdp)) {
raw_spin_lock_rcu_node(rcu_get_root(rsp)); /* irqs disabled. */
needwake = rcu_start_gp(rsp);
raw_spin_unlock_irqrestore_rcu_node(rcu_get_root(rsp), flags);
if (needwake)
rcu_gp_kthread_wake(rsp);
} else {
local_irq_restore(flags);
/* No grace period and unregistered callbacks? */
if (!rcu_gp_in_progress(rsp) &&
rcu_segcblist_is_enabled(&rdp->cblist)) {
local_irq_save(flags);
if (rcu_segcblist_restempty(&rdp->cblist, RCU_NEXT_READY_TAIL)) {
local_irq_restore(flags);
} else {
rnp = rdp->mynode;
raw_spin_lock_rcu_node(rnp); /* irqs disabled. */
needwake = rcu_accelerate_cbs(rsp, rnp, rdp);
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
if (needwake)
rcu_gp_kthread_wake(rsp);
}
}
/* If there are callbacks ready, invoke them. */
@@ -2973,11 +2861,11 @@ static void __call_rcu_core(struct rcu_state *rsp, struct rcu_data *rdp,
/* Start a new grace period if one not already started. */
if (!rcu_gp_in_progress(rsp)) {
struct rcu_node *rnp_root = rcu_get_root(rsp);
struct rcu_node *rnp = rdp->mynode;
raw_spin_lock_rcu_node(rnp_root);
needwake = rcu_start_gp(rsp);
raw_spin_unlock_rcu_node(rnp_root);
raw_spin_lock_rcu_node(rnp);
needwake = rcu_accelerate_cbs(rsp, rnp, rdp);
raw_spin_unlock_rcu_node(rnp);
if (needwake)
rcu_gp_kthread_wake(rsp);
} else {
@@ -3368,7 +3256,9 @@ static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp)
return 1;
/* Has RCU gone idle with this CPU needing another grace period? */
if (cpu_needs_another_gp(rsp, rdp))
if (!rcu_gp_in_progress(rsp) &&
rcu_segcblist_is_enabled(&rdp->cblist) &&
!rcu_segcblist_restempty(&rdp->cblist, RCU_NEXT_READY_TAIL))
return 1;
/* Has another RCU grace period completed? */
@@ -3775,6 +3665,8 @@ int rcutree_dead_cpu(unsigned int cpu)
return 0;
}
static DEFINE_PER_CPU(int, rcu_cpu_started);
/*
* Mark the specified CPU as being online so that subsequent grace periods
* (both expedited and normal) will wait on it. Note that this means that
@@ -3796,6 +3688,11 @@ void rcu_cpu_starting(unsigned int cpu)
struct rcu_node *rnp;
struct rcu_state *rsp;
if (per_cpu(rcu_cpu_started, cpu))
return;
per_cpu(rcu_cpu_started, cpu) = 1;
for_each_rcu_flavor(rsp) {
rdp = per_cpu_ptr(rsp->rda, cpu);
rnp = rdp->mynode;
@@ -3852,6 +3749,8 @@ void rcu_report_dead(unsigned int cpu)
preempt_enable();
for_each_rcu_flavor(rsp)
rcu_cleanup_dying_idle_cpu(cpu, rsp);
per_cpu(rcu_cpu_started, cpu) = 0;
}
/* Migrate the dead CPU's callbacks to the current CPU. */
@@ -3861,6 +3760,7 @@ static void rcu_migrate_callbacks(int cpu, struct rcu_state *rsp)
struct rcu_data *my_rdp;
struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
struct rcu_node *rnp_root = rcu_get_root(rdp->rsp);
bool needwake;
if (rcu_is_nocb_cpu(cpu) || rcu_segcblist_empty(&rdp->cblist))
return; /* No callbacks to migrate. */
@@ -3872,12 +3772,15 @@ static void rcu_migrate_callbacks(int cpu, struct rcu_state *rsp)
return;
}
raw_spin_lock_rcu_node(rnp_root); /* irqs already disabled. */
rcu_advance_cbs(rsp, rnp_root, rdp); /* Leverage recent GPs. */
rcu_advance_cbs(rsp, rnp_root, my_rdp); /* Assign GP to pending CBs. */
/* Leverage recent GPs and set GP for new callbacks. */
needwake = rcu_advance_cbs(rsp, rnp_root, rdp) ||
rcu_advance_cbs(rsp, rnp_root, my_rdp);
rcu_segcblist_merge(&my_rdp->cblist, &rdp->cblist);
WARN_ON_ONCE(rcu_segcblist_empty(&my_rdp->cblist) !=
!rcu_segcblist_n_cbs(&my_rdp->cblist));
raw_spin_unlock_irqrestore_rcu_node(rnp_root, flags);
if (needwake)
rcu_gp_kthread_wake(rsp);
WARN_ONCE(rcu_segcblist_n_cbs(&rdp->cblist) != 0 ||
!rcu_segcblist_empty(&rdp->cblist),
"rcu_cleanup_dead_cpu: Callbacks on offline CPU %d: qlen=%lu, 1stCB=%p\n",
@@ -4056,7 +3959,7 @@ static void __init rcu_init_one(struct rcu_state *rsp)
init_swait_queue_head(&rsp->gp_wq);
init_swait_queue_head(&rsp->expedited_wq);
rnp = rsp->level[rcu_num_lvls - 1];
rnp = rcu_first_leaf_node(rsp);
for_each_possible_cpu(i) {
while (i > rnp->grphi)
rnp++;
@@ -4168,6 +4071,7 @@ static void __init rcu_dump_rcu_node_tree(struct rcu_state *rsp)
}
struct workqueue_struct *rcu_gp_wq;
struct workqueue_struct *rcu_par_gp_wq;
void __init rcu_init(void)
{
@@ -4199,6 +4103,8 @@ void __init rcu_init(void)
/* Create workqueue for expedited GPs and for Tree SRCU. */
rcu_gp_wq = alloc_workqueue("rcu_gp", WQ_MEM_RECLAIM, 0);
WARN_ON(!rcu_gp_wq);
rcu_par_gp_wq = alloc_workqueue("rcu_par_gp", WQ_MEM_RECLAIM, 0);
WARN_ON(!rcu_par_gp_wq);
}
#include "tree_exp.h"

36
kernel/rcu/tree.h
View File

@@ -58,6 +58,14 @@ struct rcu_dynticks {
#endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
};
/* Communicate arguments to a workqueue handler. */
struct rcu_exp_work {
smp_call_func_t rew_func;
struct rcu_state *rew_rsp;
unsigned long rew_s;
struct work_struct rew_work;
};
/* RCU's kthread states for tracing. */
#define RCU_KTHREAD_STOPPED 0
#define RCU_KTHREAD_RUNNING 1
@@ -150,15 +158,32 @@ struct rcu_node {
struct swait_queue_head nocb_gp_wq[2];
/* Place for rcu_nocb_kthread() to wait GP. */
#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
int need_future_gp[2];
/* Counts of upcoming no-CB GP requests. */
u8 need_future_gp[4]; /* Counts of upcoming GP requests. */
raw_spinlock_t fqslock ____cacheline_internodealigned_in_smp;
spinlock_t exp_lock ____cacheline_internodealigned_in_smp;
unsigned long exp_seq_rq;
wait_queue_head_t exp_wq[4];
struct rcu_exp_work rew;
bool exp_need_flush; /* Need to flush workitem? */
} ____cacheline_internodealigned_in_smp;
/* Accessors for ->need_future_gp[] array. */
#define need_future_gp_mask() \
(ARRAY_SIZE(((struct rcu_node *)NULL)->need_future_gp) - 1)
#define need_future_gp_element(rnp, c) \
((rnp)->need_future_gp[(c) & need_future_gp_mask()])
#define need_any_future_gp(rnp) \
({ \
int __i; \
bool __nonzero = false; \
\
for (__i = 0; __i < ARRAY_SIZE((rnp)->need_future_gp); __i++) \
__nonzero = __nonzero || \
READ_ONCE((rnp)->need_future_gp[__i]); \
__nonzero; \
})
/*
* Bitmasks in an rcu_node cover the interval [grplo, grphi] of CPU IDs, and
* are indexed relative to this interval rather than the global CPU ID space.
@@ -224,10 +249,6 @@ struct rcu_data {
#ifdef CONFIG_RCU_FAST_NO_HZ
struct rcu_head oom_head;
#endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
atomic_long_t exp_workdone0; /* # done by workqueue. */
atomic_long_t exp_workdone1; /* # done by others #1. */
atomic_long_t exp_workdone2; /* # done by others #2. */
atomic_long_t exp_workdone3; /* # done by others #3. */
int exp_dynticks_snap; /* Double-check need for IPI. */
/* 6) Callback offloading. */
@@ -408,7 +429,6 @@ extern struct rcu_state rcu_preempt_state;
#endif /* #ifdef CONFIG_PREEMPT_RCU */
int rcu_dynticks_snap(struct rcu_dynticks *rdtp);
bool rcu_eqs_special_set(int cpu);
#ifdef CONFIG_RCU_BOOST
DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_status);
@@ -438,7 +458,6 @@ static void rcu_preempt_boost_start_gp(struct rcu_node *rnp);
static void invoke_rcu_callbacks_kthread(void);
static bool rcu_is_callbacks_kthread(void);
#ifdef CONFIG_RCU_BOOST
static void rcu_preempt_do_callbacks(void);
static int rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
struct rcu_node *rnp);
#endif /* #ifdef CONFIG_RCU_BOOST */
@@ -454,7 +473,6 @@ static void print_cpu_stall_info_end(void);
static void zero_cpu_stall_ticks(struct rcu_data *rdp);
static void increment_cpu_stall_ticks(void);
static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu);
static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq);
static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp);
static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq);
static void rcu_init_one_nocb(struct rcu_node *rnp);

241
kernel/rcu/tree_exp.h
View File

@@ -20,6 +20,8 @@
* Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
*/
#include <linux/lockdep.h>
/*
* Record the start of an expedited grace period.
*/
@@ -154,14 +156,34 @@ static void __maybe_unused sync_exp_reset_tree(struct rcu_state *rsp)
* for the current expedited grace period. Works only for preemptible
* RCU -- other RCU implementation use other means.
*
* Caller must hold the rcu_state's exp_mutex.
* Caller must hold the specificed rcu_node structure's ->lock
*/
static bool sync_rcu_preempt_exp_done(struct rcu_node *rnp)
{
raw_lockdep_assert_held_rcu_node(rnp);
return rnp->exp_tasks == NULL &&
READ_ONCE(rnp->expmask) == 0;
}
/*
* Like sync_rcu_preempt_exp_done(), but this function assumes the caller
* doesn't hold the rcu_node's ->lock, and will acquire and release the lock
* itself
*/
static bool sync_rcu_preempt_exp_done_unlocked(struct rcu_node *rnp)
{
unsigned long flags;
bool ret;
raw_spin_lock_irqsave_rcu_node(rnp, flags);
ret = sync_rcu_preempt_exp_done(rnp);
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
return ret;
}
/*
* Report the exit from RCU read-side critical section for the last task
* that queued itself during or before the current expedited preemptible-RCU
@@ -170,8 +192,7 @@ static bool sync_rcu_preempt_exp_done(struct rcu_node *rnp)
* recursively up the tree. (Calm down, calm down, we do the recursion
* iteratively!)
*
* Caller must hold the rcu_state's exp_mutex and the specified rcu_node
* structure's ->lock.
* Caller must hold the specified rcu_node structure's ->lock.
*/
static void __rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
bool wake, unsigned long flags)
@@ -207,8 +228,6 @@ static void __rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
/*
* Report expedited quiescent state for specified node. This is a
* lock-acquisition wrapper function for __rcu_report_exp_rnp().
*
* Caller must hold the rcu_state's exp_mutex.
*/
static void __maybe_unused rcu_report_exp_rnp(struct rcu_state *rsp,
struct rcu_node *rnp, bool wake)
@@ -221,8 +240,7 @@ static void __maybe_unused rcu_report_exp_rnp(struct rcu_state *rsp,
/*
* Report expedited quiescent state for multiple CPUs, all covered by the
* specified leaf rcu_node structure. Caller must hold the rcu_state's
* exp_mutex.
* specified leaf rcu_node structure.
*/
static void rcu_report_exp_cpu_mult(struct rcu_state *rsp, struct rcu_node *rnp,
unsigned long mask, bool wake)
@@ -248,14 +266,12 @@ static void rcu_report_exp_rdp(struct rcu_state *rsp, struct rcu_data *rdp,
}
/* Common code for synchronize_{rcu,sched}_expedited() work-done checking. */
static bool sync_exp_work_done(struct rcu_state *rsp, atomic_long_t *stat,
unsigned long s)
static bool sync_exp_work_done(struct rcu_state *rsp, unsigned long s)
{
if (rcu_exp_gp_seq_done(rsp, s)) {
trace_rcu_exp_grace_period(rsp->name, s, TPS("done"));
/* Ensure test happens before caller kfree(). */
smp_mb__before_atomic(); /* ^^^ */
atomic_long_inc(stat);
return true;
}
return false;
@@ -289,7 +305,7 @@ static bool exp_funnel_lock(struct rcu_state *rsp, unsigned long s)
* promoting locality and is not strictly needed for correctness.
*/
for (; rnp != NULL; rnp = rnp->parent) {
if (sync_exp_work_done(rsp, &rdp->exp_workdone1, s))
if (sync_exp_work_done(rsp, s))
return true;
/* Work not done, either wait here or go up. */
@@ -302,8 +318,7 @@ static bool exp_funnel_lock(struct rcu_state *rsp, unsigned long s)
rnp->grplo, rnp->grphi,
TPS("wait"));
wait_event(rnp->exp_wq[rcu_seq_ctr(s) & 0x3],
sync_exp_work_done(rsp,
&rdp->exp_workdone2, s));
sync_exp_work_done(rsp, s));
return true;
}
rnp->exp_seq_rq = s; /* Followers can wait on us. */
@@ -313,7 +328,7 @@ static bool exp_funnel_lock(struct rcu_state *rsp, unsigned long s)
}
mutex_lock(&rsp->exp_mutex);
fastpath:
if (sync_exp_work_done(rsp, &rdp->exp_workdone3, s)) {
if (sync_exp_work_done(rsp, s)) {
mutex_unlock(&rsp->exp_mutex);
return true;
}
@@ -361,6 +376,95 @@ static void sync_sched_exp_online_cleanup(int cpu)
WARN_ON_ONCE(ret);
}
/*
* Select the CPUs within the specified rcu_node that the upcoming
* expedited grace period needs to wait for.
*/
static void sync_rcu_exp_select_node_cpus(struct work_struct *wp)
{
int cpu;
unsigned long flags;
smp_call_func_t func;
unsigned long mask_ofl_test;
unsigned long mask_ofl_ipi;
int ret;
struct rcu_exp_work *rewp =
container_of(wp, struct rcu_exp_work, rew_work);
struct rcu_node *rnp = container_of(rewp, struct rcu_node, rew);
struct rcu_state *rsp = rewp->rew_rsp;
func = rewp->rew_func;
raw_spin_lock_irqsave_rcu_node(rnp, flags);
/* Each pass checks a CPU for identity, offline, and idle. */
mask_ofl_test = 0;
for_each_leaf_node_cpu_mask(rnp, cpu, rnp->expmask) {
unsigned long mask = leaf_node_cpu_bit(rnp, cpu);
struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
struct rcu_dynticks *rdtp = per_cpu_ptr(&rcu_dynticks, cpu);
int snap;
if (raw_smp_processor_id() == cpu ||
!(rnp->qsmaskinitnext & mask)) {
mask_ofl_test |= mask;
} else {
snap = rcu_dynticks_snap(rdtp);
if (rcu_dynticks_in_eqs(snap))
mask_ofl_test |= mask;
else
rdp->exp_dynticks_snap = snap;
}
}
mask_ofl_ipi = rnp->expmask & ~mask_ofl_test;
/*
* Need to wait for any blocked tasks as well. Note that
* additional blocking tasks will also block the expedited GP
* until such time as the ->expmask bits are cleared.
*/
if (rcu_preempt_has_tasks(rnp))
rnp->exp_tasks = rnp->blkd_tasks.next;
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
/* IPI the remaining CPUs for expedited quiescent state. */
for_each_leaf_node_cpu_mask(rnp, cpu, rnp->expmask) {
unsigned long mask = leaf_node_cpu_bit(rnp, cpu);
struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
if (!(mask_ofl_ipi & mask))
continue;
retry_ipi:
if (rcu_dynticks_in_eqs_since(rdp->dynticks,
rdp->exp_dynticks_snap)) {
mask_ofl_test |= mask;
continue;
}
ret = smp_call_function_single(cpu, func, rsp, 0);
if (!ret) {
mask_ofl_ipi &= ~mask;
continue;
}
/* Failed, raced with CPU hotplug operation. */
raw_spin_lock_irqsave_rcu_node(rnp, flags);
if ((rnp->qsmaskinitnext & mask) &&
(rnp->expmask & mask)) {
/* Online, so delay for a bit and try again. */
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
trace_rcu_exp_grace_period(rsp->name, rcu_exp_gp_seq_endval(rsp), TPS("selectofl"));
schedule_timeout_uninterruptible(1);
goto retry_ipi;
}
/* CPU really is offline, so we can ignore it. */
if (!(rnp->expmask & mask))
mask_ofl_ipi &= ~mask;
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
}
/* Report quiescent states for those that went offline. */
mask_ofl_test |= mask_ofl_ipi;
if (mask_ofl_test)
rcu_report_exp_cpu_mult(rsp, rnp, mask_ofl_test, false);
}
/*
* Select the nodes that the upcoming expedited grace period needs
* to wait for.
@@ -368,87 +472,34 @@ static void sync_sched_exp_online_cleanup(int cpu)
static void sync_rcu_exp_select_cpus(struct rcu_state *rsp,
smp_call_func_t func)
{
int cpu;
unsigned long flags;
unsigned long mask_ofl_test;
unsigned long mask_ofl_ipi;
int ret;
struct rcu_node *rnp;
trace_rcu_exp_grace_period(rsp->name, rcu_exp_gp_seq_endval(rsp), TPS("reset"));
sync_exp_reset_tree(rsp);
trace_rcu_exp_grace_period(rsp->name, rcu_exp_gp_seq_endval(rsp), TPS("select"));
/* Schedule work for each leaf rcu_node structure. */
rcu_for_each_leaf_node(rsp, rnp) {
raw_spin_lock_irqsave_rcu_node(rnp, flags);
/* Each pass checks a CPU for identity, offline, and idle. */
mask_ofl_test = 0;
for_each_leaf_node_cpu_mask(rnp, cpu, rnp->expmask) {
unsigned long mask = leaf_node_cpu_bit(rnp, cpu);
struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
struct rcu_dynticks *rdtp = per_cpu_ptr(&rcu_dynticks, cpu);
int snap;
if (raw_smp_processor_id() == cpu ||
!(rnp->qsmaskinitnext & mask)) {
mask_ofl_test |= mask;
} else {
snap = rcu_dynticks_snap(rdtp);
if (rcu_dynticks_in_eqs(snap))
mask_ofl_test |= mask;
else
rdp->exp_dynticks_snap = snap;
}
rnp->exp_need_flush = false;
if (!READ_ONCE(rnp->expmask))
continue; /* Avoid early boot non-existent wq. */
rnp->rew.rew_func = func;
rnp->rew.rew_rsp = rsp;
if (!READ_ONCE(rcu_par_gp_wq) ||
rcu_scheduler_active != RCU_SCHEDULER_RUNNING) {
/* No workqueues yet. */
sync_rcu_exp_select_node_cpus(&rnp->rew.rew_work);
continue;
}
mask_ofl_ipi = rnp->expmask & ~mask_ofl_test;
/*
* Need to wait for any blocked tasks as well. Note that
* additional blocking tasks will also block the expedited
* GP until such time as the ->expmask bits are cleared.
*/
if (rcu_preempt_has_tasks(rnp))
rnp->exp_tasks = rnp->blkd_tasks.next;
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
/* IPI the remaining CPUs for expedited quiescent state. */
for_each_leaf_node_cpu_mask(rnp, cpu, rnp->expmask) {
unsigned long mask = leaf_node_cpu_bit(rnp, cpu);
struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
if (!(mask_ofl_ipi & mask))
continue;
retry_ipi:
if (rcu_dynticks_in_eqs_since(rdp->dynticks,
rdp->exp_dynticks_snap)) {
mask_ofl_test |= mask;
continue;
}
ret = smp_call_function_single(cpu, func, rsp, 0);
if (!ret) {
mask_ofl_ipi &= ~mask;
continue;
}
/* Failed, raced with CPU hotplug operation. */
raw_spin_lock_irqsave_rcu_node(rnp, flags);
if ((rnp->qsmaskinitnext & mask) &&
(rnp->expmask & mask)) {
/* Online, so delay for a bit and try again. */
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
trace_rcu_exp_grace_period(rsp->name, rcu_exp_gp_seq_endval(rsp), TPS("selectofl"));
schedule_timeout_uninterruptible(1);
goto retry_ipi;
}
/* CPU really is offline, so we can ignore it. */
if (!(rnp->expmask & mask))
mask_ofl_ipi &= ~mask;
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
}
/* Report quiescent states for those that went offline. */
mask_ofl_test |= mask_ofl_ipi;
if (mask_ofl_test)
rcu_report_exp_cpu_mult(rsp, rnp, mask_ofl_test, false);
INIT_WORK(&rnp->rew.rew_work, sync_rcu_exp_select_node_cpus);
queue_work_on(rnp->grplo, rcu_par_gp_wq, &rnp->rew.rew_work);
rnp->exp_need_flush = true;
}
/* Wait for workqueue jobs (if any) to complete. */
rcu_for_each_leaf_node(rsp, rnp)
if (rnp->exp_need_flush)
flush_work(&rnp->rew.rew_work);
}
static void synchronize_sched_expedited_wait(struct rcu_state *rsp)
@@ -469,9 +520,9 @@ static void synchronize_sched_expedited_wait(struct rcu_state *rsp)
for (;;) {
ret = swait_event_timeout(
rsp->expedited_wq,
sync_rcu_preempt_exp_done(rnp_root),
sync_rcu_preempt_exp_done_unlocked(rnp_root),
jiffies_stall);
if (ret > 0 || sync_rcu_preempt_exp_done(rnp_root))
if (ret > 0 || sync_rcu_preempt_exp_done_unlocked(rnp_root))
return;
WARN_ON(ret < 0); /* workqueues should not be signaled. */
if (rcu_cpu_stall_suppress)
@@ -504,7 +555,7 @@ static void synchronize_sched_expedited_wait(struct rcu_state *rsp)
rcu_for_each_node_breadth_first(rsp, rnp) {
if (rnp == rnp_root)
continue; /* printed unconditionally */
if (sync_rcu_preempt_exp_done(rnp))
if (sync_rcu_preempt_exp_done_unlocked(rnp))
continue;
pr_cont(" l=%u:%d-%d:%#lx/%c",
rnp->level, rnp->grplo, rnp->grphi,
@@ -560,14 +611,6 @@ static void rcu_exp_wait_wake(struct rcu_state *rsp, unsigned long s)
mutex_unlock(&rsp->exp_wake_mutex);
}
/* Let the workqueue handler know what it is supposed to do. */
struct rcu_exp_work {
smp_call_func_t rew_func;
struct rcu_state *rew_rsp;
unsigned long rew_s;
struct work_struct rew_work;
};
/*
* Common code to drive an expedited grace period forward, used by
* workqueues and mid-boot-time tasks.
@@ -633,7 +676,7 @@ static void _synchronize_rcu_expedited(struct rcu_state *rsp,
rdp = per_cpu_ptr(rsp->rda, raw_smp_processor_id());
rnp = rcu_get_root(rsp);
wait_event(rnp->exp_wq[rcu_seq_ctr(s) & 0x3],
sync_exp_work_done(rsp, &rdp->exp_workdone0, s));
sync_exp_work_done(rsp, s));
smp_mb(); /* Workqueue actions happen before return. */
/* Let the next expedited grace period start. */

98
kernel/rcu/tree_plugin.h
View File

@@ -182,7 +182,7 @@ static void rcu_preempt_ctxt_queue(struct rcu_node *rnp, struct rcu_data *rdp)
raw_lockdep_assert_held_rcu_node(rnp);
WARN_ON_ONCE(rdp->mynode != rnp);
WARN_ON_ONCE(rnp->level != rcu_num_lvls - 1);
WARN_ON_ONCE(!rcu_is_leaf_node(rnp));
/*
* Decide where to queue the newly blocked task. In theory,
@@ -383,6 +383,50 @@ static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp)
return rnp->gp_tasks != NULL;
}
/*
* Preemptible RCU implementation for rcu_read_lock().
* Just increment ->rcu_read_lock_nesting, shared state will be updated
* if we block.
*/
void __rcu_read_lock(void)
{
current->rcu_read_lock_nesting++;
barrier(); /* critical section after entry code. */
}
EXPORT_SYMBOL_GPL(__rcu_read_lock);
/*
* Preemptible RCU implementation for rcu_read_unlock().
* Decrement ->rcu_read_lock_nesting. If the result is zero (outermost
* rcu_read_unlock()) and ->rcu_read_unlock_special is non-zero, then
* invoke rcu_read_unlock_special() to clean up after a context switch
* in an RCU read-side critical section and other special cases.
*/
void __rcu_read_unlock(void)
{
struct task_struct *t = current;
if (t->rcu_read_lock_nesting != 1) {
--t->rcu_read_lock_nesting;
} else {
barrier(); /* critical section before exit code. */
t->rcu_read_lock_nesting = INT_MIN;
barrier(); /* assign before ->rcu_read_unlock_special load */
if (unlikely(READ_ONCE(t->rcu_read_unlock_special.s)))
rcu_read_unlock_special(t);
barrier(); /* ->rcu_read_unlock_special load before assign */
t->rcu_read_lock_nesting = 0;
}
#ifdef CONFIG_PROVE_LOCKING
{
int rrln = READ_ONCE(t->rcu_read_lock_nesting);
WARN_ON_ONCE(rrln < 0 && rrln > INT_MIN / 2);
}
#endif /* #ifdef CONFIG_PROVE_LOCKING */
}
EXPORT_SYMBOL_GPL(__rcu_read_unlock);
/*
* Advance a ->blkd_tasks-list pointer to the next entry, instead
* returning NULL if at the end of the list.
@@ -489,7 +533,7 @@ void rcu_read_unlock_special(struct task_struct *t)
rnp = t->rcu_blocked_node;
raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */
WARN_ON_ONCE(rnp != t->rcu_blocked_node);
WARN_ON_ONCE(rnp->level != rcu_num_lvls - 1);
WARN_ON_ONCE(!rcu_is_leaf_node(rnp));
empty_norm = !rcu_preempt_blocked_readers_cgp(rnp);
empty_exp = sync_rcu_preempt_exp_done(rnp);
smp_mb(); /* ensure expedited fastpath sees end of RCU c-s. */
@@ -685,15 +729,6 @@ static void rcu_preempt_check_callbacks(void)
t->rcu_read_unlock_special.b.need_qs = true;
}
#ifdef CONFIG_RCU_BOOST
static void rcu_preempt_do_callbacks(void)
{
rcu_do_batch(rcu_state_p, this_cpu_ptr(rcu_data_p));
}
#endif /* #ifdef CONFIG_RCU_BOOST */
/**
* call_rcu() - Queue an RCU callback for invocation after a grace period.
* @head: structure to be used for queueing the RCU updates.
@@ -1140,7 +1175,7 @@ static void rcu_kthread_do_work(void)
{
rcu_do_batch(&rcu_sched_state, this_cpu_ptr(&rcu_sched_data));
rcu_do_batch(&rcu_bh_state, this_cpu_ptr(&rcu_bh_data));
rcu_preempt_do_callbacks();
rcu_do_batch(&rcu_preempt_state, this_cpu_ptr(&rcu_preempt_data));
}
static void rcu_cpu_kthread_setup(unsigned int cpu)
@@ -1607,7 +1642,7 @@ static int rcu_oom_notify(struct notifier_block *self,
for_each_online_cpu(cpu) {
smp_call_function_single(cpu, rcu_oom_notify_cpu, NULL, 1);
cond_resched_rcu_qs();
cond_resched_tasks_rcu_qs();
}
/* Unconditionally decrement: no need to wake ourselves up. */
@@ -1780,19 +1815,6 @@ static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq)
swake_up_all(sq);
}
/*
* Set the root rcu_node structure's ->need_future_gp field
* based on the sum of those of all rcu_node structures. This does
* double-count the root rcu_node structure's requests, but this
* is necessary to handle the possibility of a rcu_nocb_kthread()
* having awakened during the time that the rcu_node structures
* were being updated for the end of the previous grace period.
*/
static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq)
{
rnp->need_future_gp[(rnp->completed + 1) & 0x1] += nrq;
}
static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp)
{
return &rnp->nocb_gp_wq[rnp->completed & 0x1];
@@ -1966,7 +1988,7 @@ static void __call_rcu_nocb_enqueue(struct rcu_data *rdp,
trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu,
TPS("WakeOvf"));
} else {
wake_nocb_leader_defer(rdp, RCU_NOCB_WAKE,
wake_nocb_leader_defer(rdp, RCU_NOCB_WAKE_FORCE,
TPS("WakeOvfIsDeferred"));
}
rdp->qlen_last_fqs_check = LONG_MAX / 2;
@@ -2048,7 +2070,8 @@ static void rcu_nocb_wait_gp(struct rcu_data *rdp)
struct rcu_node *rnp = rdp->mynode;
raw_spin_lock_irqsave_rcu_node(rnp, flags);
needwake = rcu_start_future_gp(rnp, rdp, &c);
c = rcu_cbs_completed(rdp->rsp, rnp);
needwake = rcu_start_this_gp(rnp, rdp, c);
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
if (needwake)
rcu_gp_kthread_wake(rdp->rsp);
@@ -2057,7 +2080,7 @@ static void rcu_nocb_wait_gp(struct rcu_data *rdp)
* Wait for the grace period. Do so interruptibly to avoid messing
* up the load average.
*/
trace_rcu_future_gp(rnp, rdp, c, TPS("StartWait"));
trace_rcu_this_gp(rnp, rdp, c, TPS("StartWait"));
for (;;) {
swait_event_interruptible(
rnp->nocb_gp_wq[c & 0x1],
@@ -2065,9 +2088,9 @@ static void rcu_nocb_wait_gp(struct rcu_data *rdp)
if (likely(d))
break;
WARN_ON(signal_pending(current));
trace_rcu_future_gp(rnp, rdp, c, TPS("ResumeWait"));
trace_rcu_this_gp(rnp, rdp, c, TPS("ResumeWait"));
}
trace_rcu_future_gp(rnp, rdp, c, TPS("EndWait"));
trace_rcu_this_gp(rnp, rdp, c, TPS("EndWait"));
smp_mb(); /* Ensure that CB invocation happens after GP end. */
}
@@ -2236,7 +2259,7 @@ static int rcu_nocb_kthread(void *arg)
cl++;
c++;
local_bh_enable();
cond_resched_rcu_qs();
cond_resched_tasks_rcu_qs();
list = next;
}
trace_rcu_batch_end(rdp->rsp->name, c, !!list, 0, 0, 1);
@@ -2292,7 +2315,7 @@ static void do_nocb_deferred_wakeup(struct rcu_data *rdp)
void __init rcu_init_nohz(void)
{
int cpu;
bool need_rcu_nocb_mask = true;
bool need_rcu_nocb_mask = false;
struct rcu_state *rsp;
#if defined(CONFIG_NO_HZ_FULL)
@@ -2315,7 +2338,7 @@ void __init rcu_init_nohz(void)
#endif /* #if defined(CONFIG_NO_HZ_FULL) */
if (!cpumask_subset(rcu_nocb_mask, cpu_possible_mask)) {
pr_info("\tNote: kernel parameter 'rcu_nocbs=' contains nonexistent CPUs.\n");
pr_info("\tNote: kernel parameter 'rcu_nocbs=', 'nohz_full', or 'isolcpus=' contains nonexistent CPUs.\n");
cpumask_and(rcu_nocb_mask, cpu_possible_mask,
rcu_nocb_mask);
}
@@ -2495,10 +2518,6 @@ static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq)
{
}
static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq)
{
}
static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp)
{
return NULL;
@@ -2587,8 +2606,7 @@ static bool rcu_nohz_full_cpu(struct rcu_state *rsp)
}
/*
* Bind the grace-period kthread for the sysidle flavor of RCU to the
* timekeeping CPU.
* Bind the RCU grace-period kthreads to the housekeeping CPU.
*/
static void rcu_bind_gp_kthread(void)
{

50
kernel/rcu/update.c
View File

@@ -226,54 +226,6 @@ core_initcall(rcu_set_runtime_mode);
#endif /* #if !defined(CONFIG_TINY_RCU) || defined(CONFIG_SRCU) */
#ifdef CONFIG_PREEMPT_RCU
/*
* Preemptible RCU implementation for rcu_read_lock().
* Just increment ->rcu_read_lock_nesting, shared state will be updated
* if we block.
*/
void __rcu_read_lock(void)
{
current->rcu_read_lock_nesting++;
barrier(); /* critical section after entry code. */
}
EXPORT_SYMBOL_GPL(__rcu_read_lock);
/*
* Preemptible RCU implementation for rcu_read_unlock().
* Decrement ->rcu_read_lock_nesting. If the result is zero (outermost
* rcu_read_unlock()) and ->rcu_read_unlock_special is non-zero, then
* invoke rcu_read_unlock_special() to clean up after a context switch
* in an RCU read-side critical section and other special cases.
*/
void __rcu_read_unlock(void)
{
struct task_struct *t = current;
if (t->rcu_read_lock_nesting != 1) {
--t->rcu_read_lock_nesting;
} else {
barrier(); /* critical section before exit code. */
t->rcu_read_lock_nesting = INT_MIN;
barrier(); /* assign before ->rcu_read_unlock_special load */
if (unlikely(READ_ONCE(t->rcu_read_unlock_special.s)))
rcu_read_unlock_special(t);
barrier(); /* ->rcu_read_unlock_special load before assign */
t->rcu_read_lock_nesting = 0;
}
#ifdef CONFIG_PROVE_LOCKING
{
int rrln = READ_ONCE(t->rcu_read_lock_nesting);
WARN_ON_ONCE(rrln < 0 && rrln > INT_MIN / 2);
}
#endif /* #ifdef CONFIG_PROVE_LOCKING */
}
EXPORT_SYMBOL_GPL(__rcu_read_unlock);
#endif /* #ifdef CONFIG_PREEMPT_RCU */
#ifdef CONFIG_DEBUG_LOCK_ALLOC
static struct lock_class_key rcu_lock_key;
struct lockdep_map rcu_lock_map =
@@ -624,7 +576,7 @@ EXPORT_SYMBOL_GPL(call_rcu_tasks);
* grace period has elapsed, in other words after all currently
* executing rcu-tasks read-side critical sections have elapsed. These
* read-side critical sections are delimited by calls to schedule(),
* cond_resched_rcu_qs(), idle execution, userspace execution, calls
* cond_resched_tasks_rcu_qs(), idle execution, userspace execution, calls
* to synchronize_rcu_tasks(), and (in theory, anyway) cond_resched().
*
* This is a very specialized primitive, intended only for a few uses in

14
kernel/sched/core.c
View File

@@ -5025,20 +5025,6 @@ int __cond_resched_lock(spinlock_t *lock)
}
EXPORT_SYMBOL(__cond_resched_lock);
int __sched __cond_resched_softirq(void)
{
BUG_ON(!in_softirq());
if (should_resched(SOFTIRQ_DISABLE_OFFSET)) {
local_bh_enable();
preempt_schedule_common();
local_bh_disable();
return 1;
}
return 0;
}
EXPORT_SYMBOL(__cond_resched_softirq);
/**
* yield - yield the current processor to other threads.
*

3
kernel/softirq.c
View File

@@ -145,8 +145,7 @@ static void __local_bh_enable(unsigned int cnt)
}
/*
* Special-case - softirqs can safely be enabled in
* cond_resched_softirq(), or by __do_softirq(),
* Special-case - softirqs can safely be enabled by __do_softirq(),
* without processing still-pending softirqs:
*/
void _local_bh_enable(void)

2
kernel/torture.c
View File

@@ -574,7 +574,7 @@ void stutter_wait(const char *title)
{
int spt;
cond_resched_rcu_qs();
cond_resched_tasks_rcu_qs();
spt = READ_ONCE(stutter_pause_test);
for (; spt; spt = READ_ONCE(stutter_pause_test)) {
if (spt == 1) {

4
kernel/trace/trace_benchmark.c
View File

@@ -159,13 +159,13 @@ static int benchmark_event_kthread(void *arg)
* wants to run, schedule in, but if the CPU is idle,
* we'll keep burning cycles.
*
* Note the _rcu_qs() version of cond_resched() will
* Note the tasks_rcu_qs() version of cond_resched() will
* notify synchronize_rcu_tasks() that this thread has
* passed a quiescent state for rcu_tasks. Otherwise
* this thread will never voluntarily schedule which would
* block synchronize_rcu_tasks() indefinitely.
*/
cond_resched();
cond_resched_tasks_rcu_qs();
}
return 0;