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rcu-tasks: Drive synchronous grace periods from calling task

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This commit causes synchronous grace periods to be driven from the task
invoking synchronize_rcu_*(), allowing these functions to be invoked from
the mid-boot dead zone extending from when the scheduler was initialized
to to point that the various RCU tasks grace-period kthreads are spawned.
This change will allow the self-tests to run in a consistent manner.

Reported-by: Matthew Wilcox <willy@infradead.org>
Reported-by: Zhouyi Zhou <zhouzhouyi@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Paul E. McKenney 2022-04-19 15:41:38 -07:00
parent 68cb47204d
commit 4a8cc433b8
1 changed files with 16 additions and 8 deletions
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24
kernel/rcu/tasks.h
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@ -495,17 +495,21 @@ static void rcu_tasks_invoke_cbs_wq(struct work_struct *wp)
}
// Wait for one grace period.
static void rcu_tasks_one_gp(struct rcu_tasks *rtp)
static void rcu_tasks_one_gp(struct rcu_tasks *rtp, bool midboot)
{
int needgpcb;
mutex_lock(&rtp->tasks_gp_mutex);
set_tasks_gp_state(rtp, RTGS_WAIT_CBS);
// If there were none, wait a bit and start over.
rcuwait_wait_event(&rtp->cbs_wait,
(needgpcb = rcu_tasks_need_gpcb(rtp)),
TASK_IDLE);
if (unlikely(midboot)) {
needgpcb = 0x2;
} else {
set_tasks_gp_state(rtp, RTGS_WAIT_CBS);
rcuwait_wait_event(&rtp->cbs_wait,
(needgpcb = rcu_tasks_need_gpcb(rtp)),
TASK_IDLE);
}
if (needgpcb & 0x2) {
// Wait for one grace period.
@ -540,7 +544,7 @@ static int __noreturn rcu_tasks_kthread(void *arg)
for (;;) {
// Wait for one grace period and invoke any callbacks
// that are ready.
rcu_tasks_one_gp(rtp);
rcu_tasks_one_gp(rtp, false);
// Paranoid sleep to keep this from entering a tight loop.
schedule_timeout_idle(rtp->gp_sleep);
@ -554,8 +558,12 @@ static void synchronize_rcu_tasks_generic(struct rcu_tasks *rtp)
RCU_LOCKDEP_WARN(rcu_scheduler_active == RCU_SCHEDULER_INACTIVE,
"synchronize_rcu_tasks called too soon");
/* Wait for the grace period. */
wait_rcu_gp(rtp->call_func);
// If the grace-period kthread is running, use it.
if (READ_ONCE(rtp->kthread_ptr)) {
wait_rcu_gp(rtp->call_func);
return;
}
rcu_tasks_one_gp(rtp, true);
}
/* Spawn RCU-tasks grace-period kthread. */