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rcu: Mark accesses to rdp->rcu_cpu_has_work

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Although the rdp->rcu_cpu_has_work field is accessed only by the
corresponding CPU, it can be accessed by both interrupt handlers via
invoke_rcu_core_kthread() and at task level via rcu_cpu_kthread().
This means that we need this_cpu_read() rather than __this_cpu_read(),
this_cpu_write() rather than __this_cpu_write(), and READ_ONCE()
rather than plain C-language loads.  The exception is the boot-time
rcu_spawn_core_kthreads(), which cannot race with kthreads that have
not yet been spawned.

This commit therefore makes it so.

KCSAN located this issue.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Paul E. McKenney 2026-07-20 16:36:55 -07:00
parent 545b3ac4c1
commit 2aaee3fc84
1 changed files with 4 additions and 4 deletions
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8
kernel/rcu/tree.c
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@ -2671,7 +2671,7 @@ static void rcu_do_batch(struct rcu_data *rdp)
// reporting, so check time limits for them.
if (rdp->rcu_cpu_kthread_status == RCU_KTHREAD_RUNNING &&
rcu_do_batch_check_time(count, tlimit, jlimit_check, jlimit)) {
rdp->rcu_cpu_has_work = 1;
WRITE_ONCE(rdp->rcu_cpu_has_work, 1);
break;
}
}
@ -2931,7 +2931,7 @@ static void invoke_rcu_core_kthread(void)
unsigned long flags;
local_irq_save(flags);
__this_cpu_write(rcu_data.rcu_cpu_has_work, 1);
this_cpu_write(rcu_data.rcu_cpu_has_work, 1);
t = __this_cpu_read(rcu_data.rcu_cpu_kthread_task);
if (t != NULL && t != current)
rcu_wake_cond(t, __this_cpu_read(rcu_data.rcu_cpu_kthread_status));
@ -2958,7 +2958,7 @@ static void rcu_cpu_kthread_park(unsigned int cpu)
static int rcu_cpu_kthread_should_run(unsigned int cpu)
{
return __this_cpu_read(rcu_data.rcu_cpu_has_work);
return this_cpu_read(rcu_data.rcu_cpu_has_work);
}
/*
@ -2979,7 +2979,7 @@ static void rcu_cpu_kthread(unsigned int cpu)
local_bh_disable();
*statusp = RCU_KTHREAD_RUNNING;
local_irq_disable();
work = *workp;
work = READ_ONCE(*workp);
WRITE_ONCE(*workp, 0);
local_irq_enable();
if (work)