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rcu-tasks: Initialize callback lists at rcu_init() time 

In order for RCU Tasks to reliably maintain per-CPU lists of exiting
tasks, those lists must be initialized before it is possible for tasks
to exit, especially given that the boot CPU is not necessarily CPU 0
(an example being, powerpc kexec() kernels).  And at the time that
rcu_init_tasks_generic() is called, a task could potentially exit,
unconventional though that sort of thing might be.

This commit therefore moves the calls to cblist_init_generic() from
functions called from rcu_init_tasks_generic() to a new function named
tasks_cblist_init_generic() that is invoked from rcu_init().

This constituted a bug in a commit that never went to mainline, so
there is no need for any backporting to -stable.

Reported-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
This commit is contained in:
Paul E. McKenney 2024-02-22 12:29:54 -08:00 committed by Boqun Feng
parent bfe93930ea
commit 30ef09635b
4 changed files with 27 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
kernel/rcu/rcu.h
View File

@ -528,6 +528,12 @@ struct task_struct *get_rcu_tasks_gp_kthread(void);
struct task_struct *get_rcu_tasks_rude_gp_kthread(void);
#endif // # ifdef CONFIG_TASKS_RUDE_RCU
#ifdef CONFIG_TASKS_RCU_GENERIC
void tasks_cblist_init_generic(void);
#else /* #ifdef CONFIG_TASKS_RCU_GENERIC */
static inline void tasks_cblist_init_generic(void) { }
#endif /* #else #ifdef CONFIG_TASKS_RCU_GENERIC */
#define RCU_SCHEDULER_INACTIVE 0
#define RCU_SCHEDULER_INIT 1
#define RCU_SCHEDULER_RUNNING 2

24
kernel/rcu/tasks.h
View File

@ -242,7 +242,6 @@ static const char *tasks_gp_state_getname(struct rcu_tasks *rtp)
static void cblist_init_generic(struct rcu_tasks *rtp)
{
int cpu;
unsigned long flags;
int lim;
int shift;
@ -268,10 +267,8 @@ static void cblist_init_generic(struct rcu_tasks *rtp)
WARN_ON_ONCE(!rtpcp);
if (cpu)
raw_spin_lock_init(&ACCESS_PRIVATE(rtpcp, lock));
local_irq_save(flags); // serialize initialization
if (rcu_segcblist_empty(&rtpcp->cblist))
rcu_segcblist_init(&rtpcp->cblist);
local_irq_restore(flags);
INIT_WORK(&rtpcp->rtp_work, rcu_tasks_invoke_cbs_wq);
rtpcp->cpu = cpu;
rtpcp->rtpp = rtp;
@ -1120,7 +1117,6 @@ module_param(rcu_tasks_lazy_ms, int, 0444);
static int __init rcu_spawn_tasks_kthread(void)
{
cblist_init_generic(&rcu_tasks);
rcu_tasks.gp_sleep = HZ / 10;
rcu_tasks.init_fract = HZ / 10;
if (rcu_tasks_lazy_ms >= 0)
@ -1284,7 +1280,6 @@ module_param(rcu_tasks_rude_lazy_ms, int, 0444);
static int __init rcu_spawn_tasks_rude_kthread(void)
{
cblist_init_generic(&rcu_tasks_rude);
rcu_tasks_rude.gp_sleep = HZ / 10;
if (rcu_tasks_rude_lazy_ms >= 0)
rcu_tasks_rude.lazy_jiffies = msecs_to_jiffies(rcu_tasks_rude_lazy_ms);
@ -1916,7 +1911,6 @@ module_param(rcu_tasks_trace_lazy_ms, int, 0444);
static int __init rcu_spawn_tasks_trace_kthread(void)
{
cblist_init_generic(&rcu_tasks_trace);
if (IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB)) {
rcu_tasks_trace.gp_sleep = HZ / 10;
rcu_tasks_trace.init_fract = HZ / 10;
@ -2088,6 +2082,24 @@ late_initcall(rcu_tasks_verify_schedule_work);
static void rcu_tasks_initiate_self_tests(void) { }
#endif /* #else #ifdef CONFIG_PROVE_RCU */
void __init tasks_cblist_init_generic(void)
{
lockdep_assert_irqs_disabled();
WARN_ON(num_online_cpus() > 1);
#ifdef CONFIG_TASKS_RCU
cblist_init_generic(&rcu_tasks);
#endif
#ifdef CONFIG_TASKS_RUDE_RCU
cblist_init_generic(&rcu_tasks_rude);
#endif
#ifdef CONFIG_TASKS_TRACE_RCU
cblist_init_generic(&rcu_tasks_trace);
#endif
}
void __init rcu_init_tasks_generic(void)
{
#ifdef CONFIG_TASKS_RCU

1
kernel/rcu/tiny.c
View File

@ -261,4 +261,5 @@ void __init rcu_init(void)
{
open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
rcu_early_boot_tests();
tasks_cblist_init_generic();
}

2
kernel/rcu/tree.c
View File

@ -5165,6 +5165,8 @@ void __init rcu_init(void)
(void)start_poll_synchronize_rcu_expedited();
rcu_test_sync_prims();
tasks_cblist_init_generic();
}
#include "tree_stall.h"