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authorLinus Torvalds <torvalds@linux-foundation.org>2021-01-04 10:55:19 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2021-01-04 10:55:19 -0800
commit36bbbd0e234d817938bdc52121a0f5473b3e58f5 (patch)
tree7ca4bc8320bc75848e2b0f42328d6756f763db1d
parentf4f6a2e329523e1a795e5e5c0799feee997aa053 (diff)
parent1b04fa9900263b4e217ca2509fd778b32c2b4eb2 (diff)
Merge branch 'rcu/urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu
Pull RCU fix from Paul McKenney: "This is a fix for a regression in the v5.10 merge window, but it was reported quite late in the v5.10 process, plus generating and testing the fix took some time. The regression is due to commit 36dadef23fcc ("kprobes: Init kprobes in early_initcall") which on powerpc can use RCU Tasks before initialization, resulting in boot failures. The fix is straightforward, simply moving initialization of RCU Tasks before the early_initcall()s. The fix has been exposed to -next and kbuild test robot testing, and has been tested by the PowerPC guys" * 'rcu/urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu: rcu-tasks: Move RCU-tasks initialization to before early_initcall()
-rw-r--r--include/linux/rcupdate.h6
-rw-r--r--init/main.c1
-rw-r--r--kernel/rcu/tasks.h25
3 files changed, 28 insertions, 4 deletions
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index de0826411311..fd02c5fa60cb 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -86,6 +86,12 @@ void rcu_sched_clock_irq(int user);
void rcu_report_dead(unsigned int cpu);
void rcutree_migrate_callbacks(int cpu);
+#ifdef CONFIG_TASKS_RCU_GENERIC
+void rcu_init_tasks_generic(void);
+#else
+static inline void rcu_init_tasks_generic(void) { }
+#endif
+
#ifdef CONFIG_RCU_STALL_COMMON
void rcu_sysrq_start(void);
void rcu_sysrq_end(void);
diff --git a/init/main.c b/init/main.c
index 6feee7f11eaf..421640fca375 100644
--- a/init/main.c
+++ b/init/main.c
@@ -1518,6 +1518,7 @@ static noinline void __init kernel_init_freeable(void)
init_mm_internals();
+ rcu_init_tasks_generic();
do_pre_smp_initcalls();
lockup_detector_init();
diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index 35bdcfd84d42..36607551f966 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -241,7 +241,7 @@ static int __noreturn rcu_tasks_kthread(void *arg)
}
}
-/* Spawn RCU-tasks grace-period kthread, e.g., at core_initcall() time. */
+/* Spawn RCU-tasks grace-period kthread. */
static void __init rcu_spawn_tasks_kthread_generic(struct rcu_tasks *rtp)
{
struct task_struct *t;
@@ -564,7 +564,6 @@ static int __init rcu_spawn_tasks_kthread(void)
rcu_spawn_tasks_kthread_generic(&rcu_tasks);
return 0;
}
-core_initcall(rcu_spawn_tasks_kthread);
#if !defined(CONFIG_TINY_RCU)
void show_rcu_tasks_classic_gp_kthread(void)
@@ -692,7 +691,6 @@ static int __init rcu_spawn_tasks_rude_kthread(void)
rcu_spawn_tasks_kthread_generic(&rcu_tasks_rude);
return 0;
}
-core_initcall(rcu_spawn_tasks_rude_kthread);
#if !defined(CONFIG_TINY_RCU)
void show_rcu_tasks_rude_gp_kthread(void)
@@ -968,6 +966,11 @@ static void rcu_tasks_trace_pregp_step(void)
static void rcu_tasks_trace_pertask(struct task_struct *t,
struct list_head *hop)
{
+ // During early boot when there is only the one boot CPU, there
+ // is no idle task for the other CPUs. Just return.
+ if (unlikely(t == NULL))
+ return;
+
WRITE_ONCE(t->trc_reader_special.b.need_qs, false);
WRITE_ONCE(t->trc_reader_checked, false);
t->trc_ipi_to_cpu = -1;
@@ -1193,7 +1196,6 @@ static int __init rcu_spawn_tasks_trace_kthread(void)
rcu_spawn_tasks_kthread_generic(&rcu_tasks_trace);
return 0;
}
-core_initcall(rcu_spawn_tasks_trace_kthread);
#if !defined(CONFIG_TINY_RCU)
void show_rcu_tasks_trace_gp_kthread(void)
@@ -1222,6 +1224,21 @@ void show_rcu_tasks_gp_kthreads(void)
}
#endif /* #ifndef CONFIG_TINY_RCU */
+void __init rcu_init_tasks_generic(void)
+{
+#ifdef CONFIG_TASKS_RCU
+ rcu_spawn_tasks_kthread();
+#endif
+
+#ifdef CONFIG_TASKS_RUDE_RCU
+ rcu_spawn_tasks_rude_kthread();
+#endif
+
+#ifdef CONFIG_TASKS_TRACE_RCU
+ rcu_spawn_tasks_trace_kthread();
+#endif
+}
+
#else /* #ifdef CONFIG_TASKS_RCU_GENERIC */
static inline void rcu_tasks_bootup_oddness(void) {}
void show_rcu_tasks_gp_kthreads(void) {}

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