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rcu: Use this_cpu_{read,write}() for ->cpu_no_qs.b.exp

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Currently __this_cpu_read() and __this_cpu_write() is used to access the
->cpu_no_qs.b.exp field of the per-CPU rcu_data structure.  However,
this can fail when the accesses can happen in interrupt handlers, as
recently started being exercised by rcutorture.  This commit therefore
upgrades the uses of __this_cpu_read() and __this_cpu_write() to their
interrupt-safe counterparts this_cpu_read() and this_cpu_write().

KCSAN located this issue.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Paul E. McKenney 2026-07-16 12:53:56 -07:00
parent d972d10696
commit d2282f9bc7
2 changed files with 4 additions and 4 deletions
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4
kernel/rcu/tree_exp.h
View File

@ -731,7 +731,7 @@ static void rcu_exp_need_qs(void)
{
lockdep_assert_irqs_disabled();
ASSERT_EXCLUSIVE_WRITER_SCOPED(*this_cpu_ptr(&rcu_data.cpu_no_qs.b.exp));
__this_cpu_write(rcu_data.cpu_no_qs.b.exp, true);
this_cpu_write(rcu_data.cpu_no_qs.b.exp, true);
/* Store .exp before .rcu_urgent_qs. */
smp_store_release(this_cpu_ptr(&rcu_data.rcu_urgent_qs), true);
set_need_resched_current();
@ -870,7 +870,7 @@ static void rcu_exp_handler(void *unused)
ASSERT_EXCLUSIVE_WRITER_SCOPED(rdp->cpu_no_qs.b.exp);
if (!(READ_ONCE(rnp->expmask) & rdp->grpmask) ||
__this_cpu_read(rcu_data.cpu_no_qs.b.exp))
this_cpu_read(rcu_data.cpu_no_qs.b.exp))
return;
if (rcu_is_cpu_rrupt_from_idle() ||
(IS_ENABLED(CONFIG_PREEMPT_COUNT) && preempt_bh_enabled)) {

4
kernel/rcu/tree_plugin.h
View File

@ -599,7 +599,7 @@ rcu_preempt_deferred_qs_irqrestore(struct task_struct *t, unsigned long flags)
*/
static notrace bool rcu_preempt_need_deferred_qs(struct task_struct *t)
{
return (__this_cpu_read(rcu_data.cpu_no_qs.b.exp) ||
return (this_cpu_read(rcu_data.cpu_no_qs.b.exp) ||
READ_ONCE(t->rcu_read_unlock_special.s)) &&
rcu_preempt_depth() == 0;
}
@ -981,7 +981,7 @@ static void rcu_qs(void)
trace_rcu_grace_period(TPS("rcu_sched"),
__this_cpu_read(rcu_data.gp_seq), TPS("cpuqs"));
__this_cpu_write(rcu_data.cpu_no_qs.b.norm, false);
if (__this_cpu_read(rcu_data.cpu_no_qs.b.exp))
if (this_cpu_read(rcu_data.cpu_no_qs.b.exp))
rcu_report_exp_rdp(this_cpu_ptr(&rcu_data));
}