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rcu: Mark interrupts-enabled accesses to rdp->cpu_no_qs.b.norm

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The rdp->cpu_no_qs.b.norm field is accessed only by the current CPU,
but can be accessed both at task level and from interrupt handlers.
All accesses from interrupts-enabled code must therefore be marked.
This commit therefore converts from __this_cpu_read() to this_cpu_read(),
from __this_cpu_write() to this_cpu_write(), and plain C-language accesses
to READ_ONCE() and WRITE_ONCE(), but only in interrupts-enabled code.

KCSAN located this issue.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Paul E. McKenney 2026-07-21 21:03:06 -07:00
parent 2aaee3fc84
commit 8fe479568c
2 changed files with 5 additions and 5 deletions
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2
kernel/rcu/tree.c
View File

@ -2540,7 +2540,7 @@ rcu_check_quiescent_state(struct rcu_data *rdp)
* Was there a quiescent state since the beginning of the grace
* period? If no, then exit and wait for the next call.
*/
if (rdp->cpu_no_qs.b.norm)
if (READ_ONCE(rdp->cpu_no_qs.b.norm))
return;
/*

8
kernel/rcu/tree_plugin.h
View File

@ -298,11 +298,11 @@ static void rcu_preempt_ctxt_queue(struct rcu_node *rnp, struct rcu_data *rdp)
static void rcu_qs(void)
{
RCU_LOCKDEP_WARN(preemptible(), "rcu_qs() invoked with preemption enabled!!!\n");
if (__this_cpu_read(rcu_data.cpu_no_qs.b.norm)) {
if (this_cpu_read(rcu_data.cpu_no_qs.b.norm)) {
trace_rcu_grace_period(TPS("rcu_preempt"),
__this_cpu_read(rcu_data.gp_seq),
TPS("cpuqs"));
__this_cpu_write(rcu_data.cpu_no_qs.b.norm, false);
this_cpu_write(rcu_data.cpu_no_qs.b.norm, false);
barrier(); /* Coordinate with rcu_flavor_sched_clock_irq(). */
WRITE_ONCE(current->rcu_read_unlock_special.b.need_qs, false);
}
@ -952,7 +952,7 @@ void rcu_read_unlock_strict(void)
* __rcu_read_unlock().
*/
rdp = this_cpu_ptr(&rcu_data);
rdp->cpu_no_qs.b.norm = false;
WRITE_ONCE(rdp->cpu_no_qs.b.norm, false);
rcu_report_qs_rdp(rdp);
udelay(rcu_unlock_delay);
}
@ -980,7 +980,7 @@ static void rcu_qs(void)
return;
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);
this_cpu_write(rcu_data.cpu_no_qs.b.norm, false);
if (this_cpu_read(rcu_data.cpu_no_qs.b.exp))
rcu_report_exp_rdp(this_cpu_ptr(&rcu_data));
}