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-rw-r--r--kernel/locking/locktorture.c18
-rw-r--r--kernel/rcu/Kconfig.debug25
-rw-r--r--kernel/rcu/rcu.h8
-rw-r--r--kernel/rcu/rcutorture.c16
-rw-r--r--kernel/rcu/srcutree.c24
-rw-r--r--kernel/rcu/tasks.h4
-rw-r--r--kernel/rcu/tree.c2
-rw-r--r--kernel/rcu/tree_stall.h11
-rw-r--r--kernel/rcu/update.c6
9 files changed, 80 insertions, 34 deletions
diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
index 69d3cd2cfc3b..415d81e6ce70 100644
--- a/kernel/locking/locktorture.c
+++ b/kernel/locking/locktorture.c
@@ -124,7 +124,7 @@ struct call_rcu_chain {
struct rcu_head crc_rh;
bool crc_stop;
};
-struct call_rcu_chain *call_rcu_chain;
+struct call_rcu_chain *call_rcu_chain_list;
/* Forward reference. */
static void lock_torture_cleanup(void);
@@ -1074,12 +1074,12 @@ static int call_rcu_chain_init(void)
if (call_rcu_chains <= 0)
return 0;
- call_rcu_chain = kcalloc(call_rcu_chains, sizeof(*call_rcu_chain), GFP_KERNEL);
- if (!call_rcu_chain)
+ call_rcu_chain_list = kcalloc(call_rcu_chains, sizeof(*call_rcu_chain_list), GFP_KERNEL);
+ if (!call_rcu_chain_list)
return -ENOMEM;
for (i = 0; i < call_rcu_chains; i++) {
- call_rcu_chain[i].crc_stop = false;
- call_rcu(&call_rcu_chain[i].crc_rh, call_rcu_chain_cb);
+ call_rcu_chain_list[i].crc_stop = false;
+ call_rcu(&call_rcu_chain_list[i].crc_rh, call_rcu_chain_cb);
}
return 0;
}
@@ -1089,13 +1089,13 @@ static void call_rcu_chain_cleanup(void)
{
int i;
- if (!call_rcu_chain)
+ if (!call_rcu_chain_list)
return;
for (i = 0; i < call_rcu_chains; i++)
- smp_store_release(&call_rcu_chain[i].crc_stop, true);
+ smp_store_release(&call_rcu_chain_list[i].crc_stop, true);
rcu_barrier();
- kfree(call_rcu_chain);
- call_rcu_chain = NULL;
+ kfree(call_rcu_chain_list);
+ call_rcu_chain_list = NULL;
}
static void lock_torture_cleanup(void)
diff --git a/kernel/rcu/Kconfig.debug b/kernel/rcu/Kconfig.debug
index 2984de629f74..9b0b52e1836f 100644
--- a/kernel/rcu/Kconfig.debug
+++ b/kernel/rcu/Kconfig.debug
@@ -105,6 +105,31 @@ config RCU_CPU_STALL_CPUTIME
The boot option rcupdate.rcu_cpu_stall_cputime has the same function
as this one, but will override this if it exists.
+config RCU_CPU_STALL_NOTIFIER
+ bool "Provide RCU CPU-stall notifiers"
+ depends on RCU_STALL_COMMON
+ depends on DEBUG_KERNEL
+ depends on RCU_EXPERT
+ default n
+ help
+ WARNING: You almost certainly do not want this!!!
+
+ Enable RCU CPU-stall notifiers, which are invoked just before
+ printing the RCU CPU stall warning. As such, bugs in notifier
+ callbacks can prevent stall warnings from being printed.
+ And the whole reason that a stall warning is being printed is
+ that something is hung up somewhere. Therefore, the notifier
+ callbacks must be written extremely carefully, preferably
+ containing only lockless code. After all, it is quite possible
+ that the whole reason that the RCU CPU stall is happening in
+ the first place is that someone forgot to release whatever lock
+ that you are thinking of acquiring. In which case, having your
+ notifier callback acquire that lock will hang, preventing the
+ RCU CPU stall warning from appearing.
+
+ Say Y here if you want RCU CPU stall notifiers (you don't want them)
+ Say N if you are unsure.
+
config RCU_TRACE
bool "Enable tracing for RCU"
depends on DEBUG_KERNEL
diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
index b531c33e9545..f94f65877f2b 100644
--- a/kernel/rcu/rcu.h
+++ b/kernel/rcu/rcu.h
@@ -262,6 +262,8 @@ static inline bool rcu_stall_is_suppressed_at_boot(void)
return rcu_cpu_stall_suppress_at_boot && !rcu_inkernel_boot_has_ended();
}
+extern int rcu_cpu_stall_notifiers;
+
#ifdef CONFIG_RCU_STALL_COMMON
extern int rcu_cpu_stall_ftrace_dump;
@@ -659,10 +661,10 @@ static inline bool rcu_cpu_beenfullyonline(int cpu) { return true; }
bool rcu_cpu_beenfullyonline(int cpu);
#endif
-#ifdef CONFIG_RCU_STALL_COMMON
+#if defined(CONFIG_RCU_STALL_COMMON) && defined(CONFIG_RCU_CPU_STALL_NOTIFIER)
int rcu_stall_notifier_call_chain(unsigned long val, void *v);
-#else // #ifdef CONFIG_RCU_STALL_COMMON
+#else // #if defined(CONFIG_RCU_STALL_COMMON) && defined(CONFIG_RCU_CPU_STALL_NOTIFIER)
static inline int rcu_stall_notifier_call_chain(unsigned long val, void *v) { return NOTIFY_DONE; }
-#endif // #else // #ifdef CONFIG_RCU_STALL_COMMON
+#endif // #else // #if defined(CONFIG_RCU_STALL_COMMON) && defined(CONFIG_RCU_CPU_STALL_NOTIFIER)
#endif /* __LINUX_RCU_H */
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 30fc9d34e329..7567ca8e743c 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -2450,10 +2450,12 @@ static int rcu_torture_stall(void *args)
unsigned long stop_at;
VERBOSE_TOROUT_STRING("rcu_torture_stall task started");
- ret = rcu_stall_chain_notifier_register(&rcu_torture_stall_block);
- if (ret)
- pr_info("%s: rcu_stall_chain_notifier_register() returned %d, %sexpected.\n",
- __func__, ret, !IS_ENABLED(CONFIG_RCU_STALL_COMMON) ? "un" : "");
+ if (rcu_cpu_stall_notifiers) {
+ ret = rcu_stall_chain_notifier_register(&rcu_torture_stall_block);
+ if (ret)
+ pr_info("%s: rcu_stall_chain_notifier_register() returned %d, %sexpected.\n",
+ __func__, ret, !IS_ENABLED(CONFIG_RCU_STALL_COMMON) ? "un" : "");
+ }
if (stall_cpu_holdoff > 0) {
VERBOSE_TOROUT_STRING("rcu_torture_stall begin holdoff");
schedule_timeout_interruptible(stall_cpu_holdoff * HZ);
@@ -2497,7 +2499,7 @@ static int rcu_torture_stall(void *args)
cur_ops->readunlock(idx);
}
pr_alert("%s end.\n", __func__);
- if (!ret) {
+ if (rcu_cpu_stall_notifiers && !ret) {
ret = rcu_stall_chain_notifier_unregister(&rcu_torture_stall_block);
if (ret)
pr_info("%s: rcu_stall_chain_notifier_unregister() returned %d.\n", __func__, ret);
@@ -3872,7 +3874,9 @@ rcu_torture_init(void)
}
if (fqs_duration < 0)
fqs_duration = 0;
- if (fqs_duration) {
+ if (fqs_holdoff < 0)
+ fqs_holdoff = 0;
+ if (fqs_duration && fqs_holdoff) {
/* Create the fqs thread */
firsterr = torture_create_kthread(rcu_torture_fqs, NULL,
fqs_task);
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index 560e99ec5333..0351a4e83529 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -772,20 +772,10 @@ EXPORT_SYMBOL_GPL(__srcu_read_unlock_nmisafe);
*/
static void srcu_gp_start(struct srcu_struct *ssp)
{
- struct srcu_data *sdp;
int state;
- if (smp_load_acquire(&ssp->srcu_sup->srcu_size_state) < SRCU_SIZE_WAIT_BARRIER)
- sdp = per_cpu_ptr(ssp->sda, get_boot_cpu_id());
- else
- sdp = this_cpu_ptr(ssp->sda);
lockdep_assert_held(&ACCESS_PRIVATE(ssp->srcu_sup, lock));
WARN_ON_ONCE(ULONG_CMP_GE(ssp->srcu_sup->srcu_gp_seq, ssp->srcu_sup->srcu_gp_seq_needed));
- spin_lock_rcu_node(sdp); /* Interrupts already disabled. */
- rcu_segcblist_advance(&sdp->srcu_cblist,
- rcu_seq_current(&ssp->srcu_sup->srcu_gp_seq));
- WARN_ON_ONCE(!rcu_segcblist_segempty(&sdp->srcu_cblist, RCU_NEXT_TAIL));
- spin_unlock_rcu_node(sdp); /* Interrupts remain disabled. */
WRITE_ONCE(ssp->srcu_sup->srcu_gp_start, jiffies);
WRITE_ONCE(ssp->srcu_sup->srcu_n_exp_nodelay, 0);
smp_mb(); /* Order prior store to ->srcu_gp_seq_needed vs. GP start. */
@@ -1271,9 +1261,11 @@ static unsigned long srcu_gp_start_if_needed(struct srcu_struct *ssp,
* period (gp_num = X + 8). So acceleration fails.
*/
s = rcu_seq_snap(&ssp->srcu_sup->srcu_gp_seq);
- rcu_segcblist_advance(&sdp->srcu_cblist,
- rcu_seq_current(&ssp->srcu_sup->srcu_gp_seq));
- WARN_ON_ONCE(!rcu_segcblist_accelerate(&sdp->srcu_cblist, s) && rhp);
+ if (rhp) {
+ rcu_segcblist_advance(&sdp->srcu_cblist,
+ rcu_seq_current(&ssp->srcu_sup->srcu_gp_seq));
+ WARN_ON_ONCE(!rcu_segcblist_accelerate(&sdp->srcu_cblist, s));
+ }
if (ULONG_CMP_LT(sdp->srcu_gp_seq_needed, s)) {
sdp->srcu_gp_seq_needed = s;
needgp = true;
@@ -1723,6 +1715,11 @@ static void srcu_invoke_callbacks(struct work_struct *work)
WARN_ON_ONCE(!rcu_segcblist_segempty(&sdp->srcu_cblist, RCU_NEXT_TAIL));
rcu_segcblist_advance(&sdp->srcu_cblist,
rcu_seq_current(&ssp->srcu_sup->srcu_gp_seq));
+ /*
+ * Although this function is theoretically re-entrant, concurrent
+ * callbacks invocation is disallowed to avoid executing an SRCU barrier
+ * too early.
+ */
if (sdp->srcu_cblist_invoking ||
!rcu_segcblist_ready_cbs(&sdp->srcu_cblist)) {
spin_unlock_irq_rcu_node(sdp);
@@ -1753,6 +1750,7 @@ static void srcu_invoke_callbacks(struct work_struct *work)
sdp->srcu_cblist_invoking = false;
more = rcu_segcblist_ready_cbs(&sdp->srcu_cblist);
spin_unlock_irq_rcu_node(sdp);
+ /* An SRCU barrier or callbacks from previous nesting work pending */
if (more)
srcu_schedule_cbs_sdp(sdp, 0);
}
diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index f54d5782eca0..732ad5b39946 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -975,7 +975,7 @@ static void check_holdout_task(struct task_struct *t,
t->rcu_tasks_nvcsw != READ_ONCE(t->nvcsw) ||
!rcu_tasks_is_holdout(t) ||
(IS_ENABLED(CONFIG_NO_HZ_FULL) &&
- !is_idle_task(t) && t->rcu_tasks_idle_cpu >= 0)) {
+ !is_idle_task(t) && READ_ONCE(t->rcu_tasks_idle_cpu) >= 0)) {
WRITE_ONCE(t->rcu_tasks_holdout, false);
list_del_init(&t->rcu_tasks_holdout_list);
put_task_struct(t);
@@ -993,7 +993,7 @@ static void check_holdout_task(struct task_struct *t,
t, ".I"[is_idle_task(t)],
"N."[cpu < 0 || !tick_nohz_full_cpu(cpu)],
t->rcu_tasks_nvcsw, t->nvcsw, t->rcu_tasks_holdout,
- t->rcu_tasks_idle_cpu, cpu);
+ data_race(t->rcu_tasks_idle_cpu), cpu);
sched_show_task(t);
}
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 3ac3c846105f..1ae851777806 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2338,6 +2338,8 @@ void rcu_force_quiescent_state(void)
struct rcu_node *rnp;
struct rcu_node *rnp_old = NULL;
+ if (!rcu_gp_in_progress())
+ return;
/* Funnel through hierarchy to reduce memory contention. */
rnp = raw_cpu_read(rcu_data.mynode);
for (; rnp != NULL; rnp = rnp->parent) {
diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index ac8e86babe44..5d666428546b 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -1061,6 +1061,7 @@ static int __init rcu_sysrq_init(void)
}
early_initcall(rcu_sysrq_init);
+#ifdef CONFIG_RCU_CPU_STALL_NOTIFIER
//////////////////////////////////////////////////////////////////////////////
//
@@ -1081,7 +1082,13 @@ static ATOMIC_NOTIFIER_HEAD(rcu_cpu_stall_notifier_list);
*/
int rcu_stall_chain_notifier_register(struct notifier_block *n)
{
- return atomic_notifier_chain_register(&rcu_cpu_stall_notifier_list, n);
+ int rcsn = rcu_cpu_stall_notifiers;
+
+ WARN(1, "Adding %pS() to RCU stall notifier list (%s).\n", n->notifier_call,
+ rcsn ? "possibly suppressing RCU CPU stall warnings" : "failed, so all is well");
+ if (rcsn)
+ return atomic_notifier_chain_register(&rcu_cpu_stall_notifier_list, n);
+ return -EEXIST;
}
EXPORT_SYMBOL_GPL(rcu_stall_chain_notifier_register);
@@ -1115,3 +1122,5 @@ int rcu_stall_notifier_call_chain(unsigned long val, void *v)
{
return atomic_notifier_call_chain(&rcu_cpu_stall_notifier_list, val, v);
}
+
+#endif // #ifdef CONFIG_RCU_CPU_STALL_NOTIFIER
diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index c534d6806d3d..46aaaa9fe339 100644
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -538,9 +538,15 @@ long torture_sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
EXPORT_SYMBOL_GPL(torture_sched_setaffinity);
#endif
+int rcu_cpu_stall_notifiers __read_mostly; // !0 = provide stall notifiers (rarely useful)
+EXPORT_SYMBOL_GPL(rcu_cpu_stall_notifiers);
+
#ifdef CONFIG_RCU_STALL_COMMON
int rcu_cpu_stall_ftrace_dump __read_mostly;
module_param(rcu_cpu_stall_ftrace_dump, int, 0644);
+#ifdef CONFIG_RCU_CPU_STALL_NOTIFIER
+module_param(rcu_cpu_stall_notifiers, int, 0444);
+#endif // #ifdef CONFIG_RCU_CPU_STALL_NOTIFIER
int rcu_cpu_stall_suppress __read_mostly; // !0 = suppress stall warnings.
EXPORT_SYMBOL_GPL(rcu_cpu_stall_suppress);
module_param(rcu_cpu_stall_suppress, int, 0644);
generated by cgit v1.2.3-70-g09d2 (git 2.47.1) at 2025-01-26 02:20:06 +0000